Is eating meat good for you? The answer is an emphatic yes—and here’s the research to prove it.

Table of Contents

Nutrient Density and Bioavailability

Kerstetter JE, Wall DE, O’Brien KO, Caseria DM, Insogna KL. Meat and soy protein affect calcium homeostasis in healthy women. J Nutr. 2006;136(7):1890–1895. https://academic.oup.com/jn/article/136/7/1890/4664693 .

Intestinal absorption of calcium is lower when soy protein is consumed instead of meat protein. The high phytic acid content of soy is responsible for decreased calcium bioavailability because phytate strongly chelates multivalent metal ions, including zinc, calcium, and iron. Rutherfurd SM, Fanning AC, Miller BJ, Moughan PJ. Protein digestibility-corrected amino acid scores and digestible indispensable amino acid scores differentially describe protein quality in growing male rats. J Nutr. 2015;145(2):372–379. https://www.ncbi.nlm.nih.gov/pubmed/?term=25644361 .

Animal proteins are more bioavailable than plant proteins. Protein digestibility-corrected amino acids scores (PDCAAS), a measure of protein bioavailability that combines the amino acid profile of a protein with a measure of how much is absorbed during digestion, are significantly higher for whey, casein, egg, and beef protein than for soy, rice, pea, hemp, spirulina, and chlorella protein.

Nutrient Deficiencies in Vegan and Vegetarian Diets

Iron Deficiency

Wilson AK, Ball MJ. Nutrient intake and iron status of Australian male vegetarians. Eur J Clin Nutr. 1999;53(3):189–194. https://www.ncbi.nlm.nih.gov/pubmed/10201799 .

Despite having higher iron intakes than omnivores, Australian male vegetarians and vegans have serum ferritin concentrations that are 29 to 49 percent lower. This may be due to the poor bioavailability of iron in vegetarian and vegan diets.

Iodine Deficiency

Leung AM, Lamar A, He X, Braverman LE, Pearce EN. Iodine status and thyroid function of Boston-area vegetarians and vegans. J Clin Endocrinol Metab. 2011;96(8):E1303–E1307. https://www.ncbi.nlm.nih.gov/pubmed/21613354 .

The mean urine iodine level in vegans in Boston was less than half the level of comparable omnivores in the general U.S. population. This finding suggests that vegans are at risk of iodine deficiency. Elorinne A-L, Alfthan G, Erlund I, Kivimäki H, Paju A, Salminen I, Turpeinen U, Voutilainen S, Laakso J. Food and nutrient intake and nutritional status of Finnish vegans and non-vegetarians. PLoS One. 2016;11(3):e0151296. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0148235 .

In Finnish vegans, long-term consumption of a vegan diet is associated with lower levels of iodine compared to omnivores.

Choline Deficiency

Kim S, Fenech MF, Kim P-J. Nutritionally recommended food for semi- to strict vegetarian diets based on large-scale nutrient composition data. Sci Reports. 2018;8:4344. https://www.nature.com/articles/s41598-018-22691-1#Tab2 .

The Standard American Diet, vegan, and vegetarian diets all pose a risk of choline deficiency, among many other nutrients.

Selenium Deficiency

Schultz TD, Leklem JE. Selenium status of vegetarians, nonvegetarians, and hormone-dependent cancer subjects. Am J Clin Nutr. 1983;37(1):114–118. https://academic.oup.com/ajcn/article-abstract/37/1/114/4690821?redirectedFrom=PDF .

Seventh Day Adventists (vegetarians) have significantly lower blood selenium levels compared to omnivores. Elorinne AL, Alfthan G, Erlund I, Kivimäki H, Paju A, Salminen I, Turpeinen U, Voutilainen S, Laakso J. Food and nutrient intake and nutritional status of Finnish vegans and non-vegetarians. PLoS One. 2016;11(3):e0151296. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0148235 .

Finnish vegans have lower blood selenium levels than omnivores. Kadrabová J, Madaric A, Kováciková Z, Ginter E. Selenium status, plasma zinc, copper, and magnesium in vegetarians. Biol Trace Elem Res. 1995;50(1):13–24. https://www.ncbi.nlm.nih.gov/pubmed/8546880 .

Vegetarians have low levels of selenium, along with other essential antioxidant trace elements such as zinc and copper. This may lead to impaired antioxidant activity.

Amino Acid Deficiencies

Rae C, Digney AL, McEwan SR, Bates TC. Oral creatine monohydrate supplementation improves brain performance: a double-blind, placebo-controlled, cross-over trial. Proc Biol Sci. 2003;270(1529):2147–2150. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1691485/ .

Six weeks of oral creatine supplementation significantly improved vegetarians’ performance on tests of fluid intelligence and working memory. The difference in test scores between supplemented vegetarians and non-supplemented vegetarians was enormous, suggesting that vegetarians may have impaired cognitive processing due to creatine deficiency. Benton D, Donohoe R. The influence of creatine supplementation on the cognitive functioning of vegetarians and omnivores. Br J Nutr. 2011;105(7):1100–1105. https://www.ncbi.nlm.nih.gov/pubmed/21118604 .

Creatine supplementation resulted in better memory in vegetarians but not in omnivores, suggesting that chronic creatine deficiency may impair memory in vegetarians. Laidlaw SA, Shultz TD, Cecchino JT, Kopple JD. Plasma and urine taurine levels in vegans. Am J Clin Nutr. 1988;47(4):660–663. https://www.ncbi.nlm.nih.gov/pubmed/3354491 .

Vegetarians and vegans have a low taurine intake and low plasma and urinary taurine. Taurine is crucial for neurodevelopment, and a low taurine intake in children is associated with reduced scores on the Bayley mental development test and the WISC-R arithmetic test. Schmidt JA, Rinaldi S, Scalbert A, Ferrari P, Achaintre D, Gunter MJ, Appleby PN, Key TJ, Travis RC. Plasma concentrations and intakes of amino acids in male meat-eaters, fish-eaters, vegetarians and vegans: a cross-sectional analysis in the EPIC-Oxford cohort. Eur J Clin Nutr. 2016;70(3):306–312. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4705437/ .

Vegans don’t consume as much glycine as omnivores, even though their blood levels are higher. Everaert I, Mooyaart A, Baguet A, Zutinic A, Baelde H, Achten E, Taes Y, De Heer E, Derave W. Vegetarianism, female gender and increasing age, but not CNDP1 genotype, are associated with reduced muscle carnosine levels in humans. Amino Acids. 2011;40(4):1221–1229. https://link.springer.com/article/10.1007/s00726-010-0749-2 .

Vegetarians have a lower muscle content of carnosine, an amino acid that protects against degenerative processes, than omnivores. Kim S, Fenech MF, Kim P-J. Nutritionally recommended food for semi- to strict vegetarian diets based on large-scale nutrient composition data. Sci Reports. 2018;8:4344. https://www.nature.com/articles/s41598-018-22691-1#Tab2 .

Vegans are at risk for methionine deficiency because most high-methionine foods are animal foods such as beef, lamb, turkey, pork, fish, and cheese. Too little methionine may impair detoxification processes and reduce fertility. Pannemans DL, Wagenmakers AJ, Westerterp KR, Schaafsma G, Halliday D. Effect of protein source and quantity on protein metabolism in elderly women. Am J Clin Nutr. 1998;68(6):1228–1235. https://www.ncbi.nlm.nih.gov/pubmed/9846851 .

High-animal-protein diets produce a greater net protein synthesis in the body than plant-based protein diets. Optimal net protein synthesis is important for growth, tissue repair, and prevention of muscle catabolism in elderly people.

B12 Deficiency

Herbert V. Staging vitamin B-12 (cobalamin) status in vegetarians. Am J Clin Nutr. 1994;59(5 Suppl):1213S–1222S. https://www.ncbi.nlm.nih.gov/pubmed/8172125 .

B12 deficiency progresses through four stages: 1) plasma and cell stores of B12 become depleted, with resulting decreases in holo-TCII; 2) cell stores of B12 become low enough to decrease haptocorrin (a B12-transporting protein) and RBC B12; 3) biochemical deficiency occurs, resulting in slowed DNA synthesis and elevated serum homocysteine and serum/urine MMA; 4) clinical B12 deficiency occurs, with symptoms such as macrocytic anemia and neurological impairment. Holo-TCII is thus a much earlier indicator of B12 deficiency than total serum B12. In addition, calcium deficiency, which is common in vegans, can lead to B12 deficiency because calcium is required for B12 absorption. Herrmann W, Schorr H, Obeid R, Geisel J. Vitamin B-12 status, particularly holotranscobalamin II and methylmalonic acid concentrations, and hyperhomocysteinemia in vegetarians. Am J Clin Nutr. 2003;78(1):131–136. https://www.ncbi.nlm.nih.gov/pubmed/12816782 .

When more sensitive methods for testing B12 are used (holotranscobalamin II rather than serum B12) there is a much greater discrepancy in B12 status among vegans, vegetarians, and omnivores than previously believed, with 77 percent of vegetarians, 92 percent of vegans, and only 11 percent of omnivores demonstrating B12 deficiency. Signs of B12 deficiency such as elevated MCV may be obscured in vegetarians and vegans due to high rates of iron deficiency and high folate intakes, which reduce MCV and “cancel out” any increase that B12 deficiency would cause. This further delays the diagnosis of B12 deficiency in these populations. B12 deficiency in these populations can lead to hyperhomocysteinemia, a risk factor for cardiovascular disease. Pawlak R, Parrott SJ, Raj S, Cullum-Dugan D, Lucas D. How prevalent is vitamin B(12) deficiency among vegetarians? Nutr Rev. 2013;71(2):110–117. https://www.ncbi.nlm.nih.gov/pubmed/23356638 .

When holotranscobalamin II is used as a marker of B12 deficiency, 90 percent of vegans are found to be deficient. Furthermore, the prevalence of B12 deficiency is high in vegan/vegetarian children: in studies of U.S. and New Zealand kids following macrobiotic and lacto-ovo vegetarian diets, respectively, the prevalence of B12 deficiency was 67 percent in the U.S. kids and 50 percent in the New Zealand kids. Another study of Norwegian infants on a macrobiotic diet (born to macrobiotic mothers) found that 85 percent were B12 deficient. Bjørke Monsen AL, Ueland PM, Vollset SE, Guttormsen AB, Markestad T, Solheim E, Refsum H. Determinants of cobalamin status in newborns. Pediatrics. 2001;108(3):624–630. https://www.ncbi.nlm.nih.gov/pubmed/11533328 .

B12 status in infants is strongly correlated with maternal B12 status. Decreased maternal serum B12 is associated with impaired B12 function, as indicated by elevated MMA, in newborn infants. Specker BL, Miller D, Norman EJ, Greene H, Hayes KC. Increased urinary methylmalonic acid excretion in breast-fed infants of vegetarian mothers and identification of an acceptable dietary source of vitamin B-12. Am J Clin Nutr. 1988;47(1):89–92. https://www.ncbi.nlm.nih.gov/pubmed/3337042 .

Infant urinary MMA concentrations correlated positively with the urinary MMA of their mothers, indicating that maternal B12 status directly impacts B12 status in their offspring. Specker BL, Black A, Allen L, Morrow F. Vitamin B-12: low milk concentrations are related to low serum concentrations in vegetarian women and to methylmalonic aciduria in their infants. Am J Clin Nutr. 1990;52(6):1073–1076. https://www.ncbi.nlm.nih.gov/pubmed/2239784 .

The longer a mother has been a vegetarian, the greater the likelihood she’ll have low serum and breast milk B12 levels that correlate with B12 deficiency in her infant. Van Dusseldorp M, Schneede J, Refsum H, Ueland PM, Thomas CM, de Boer E, van Staveren WA. Risk of persistent cobalamin deficiency in adolescents fed a macrobiotic diet in early life. Am J Clin Nutr. 1999;69(4):664–671. https://www.ncbi.nlm.nih.gov/pubmed/10197567 .

Children raised on a vegan (macrobiotic) diet are at risk for B12 deficiency even after transitioning to an omnivorous diet. Moderate animal food consumption is not sufficient for restoring healthy B12 status in these individuals. Louwman MW, van Dusseldorp M, van de Vijver FJ, Thomas CM, Schneede J, Ueland PM, Refsum H, van Staveren WA. Signs of impaired cognitive function in adolescents with marginal cobalamin status. Am J Clin Nutr. 2000;72(3):762–769. https://www.ncbi.nlm.nih.gov/pubmed/10966896 .

B12 deficiency leads to impaired cognitive performance in adolescents. Rogers LM, Boy E, Miller JW, Green R, Casterline Sabel C, Allen LH. High prevalence of cobalamin deficiency in Guatemalan schoolchildren: associations with low plasma holotranscobalamin II and elevated serum methylmalonic acid and plasma homocysteine concentrations. Am J Clin Nutr. 2003;77(2):433–440. https://academic.oup.com/ajcn/article/77/2/433/4689696 .

Guatemalan children with B12 deficiency demonstrate impaired reasoning, short-term memory, and perception compared to kids with adequate B12 status. Donaldson MS. Metabolic vitamin B12 status on a mostly raw vegan diet with follow-up using tablets, nutritional yeast, or probiotic supplements. Ann Nutr Metab. 2000;44(5–6):229–234. https://www.ncbi.nlm.nih.gov/pubmed/11146329 .

It is a myth that it takes 20 years to develop a B12 deficiency. A study of raw food vegans found that 47 percent were B12 deficient after an average of two to four years on the diet. Elmadfa I, Singer I. Vitamin B-12 and homocysteine status among vegetarians: a global perspective. Am J Clin Nutr. 2009;89(5):1693S–1698S. https://academic.oup.com/ajcn/article/89/5/1693S/4596963 .

Though some studies have shown a reduced risk of circulatory problems among vegans compared with non-vegetarians, other studies report a higher risk of cardiovascular disease among vegans compared with lacto-ovo vegetarians and even omnivores.The low B12 status of vegetarians and vegans increases homocysteine, which is a risk factor for cardiovascular disease. Thus, vegetarians and vegans with low B12 status are predisposed to developing circulatory problems regardless of their favorable profile of traditional heart disease risk factors such as low serum lipids and glucose. Obersby D, Chappell DC, Dunnett A, Tsiami AA. Plasma total homocysteine status of vegetarians compared with omnivores: a systematic review and meta-analysis. Br J Nutr. 2013;109(5):785–794. https://www.ncbi.nlm.nih.gov/pubmed/23298782 .

Average homocysteine levels among vegetarians are 13.9 micromol/L, 16.4 micromol/L for vegans, and 11.3 micromol/L for omnivores. This puts vegetarians and vegans in a homocysteine range that carries a significant risk of cardiovascular disease. Woo KS, Kwok TCY, Celermajer DS. Vegan diet, subnormal vitamin B-12 status and cardiovascular health. Nutrients. 2014;6(8):3259–3273. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4145307/ .

Studies have demonstrated impaired arterial endothelial function and increased carotid intima thickness in vitamin B12-deficient populations such as vegans. This increases the risk of atherosclerosis-related diseases. Pawlak R. Is vitamin B12 deficiency a risk factor for cardiovascular disease in vegetarians? Am J Prev Med. 2015;48(6):e11–26. https://www.ncbi.nlm.nih.gov/pubmed/25998928 .

When data on circulatory death rate ratios and cerebrovascular disease death are assessed, some cohorts demonstrate higher death rates among vegetarians and vegans compared to omnivores. This may be attributed to the lower B12 status and higher homocysteine concentrations among vegetarians and vegans. Vitamin B12 deficiency may therefore negate the purported cardiovascular disease prevention benefits of vegetarian diets.

The Effects of Vegetarianism and Veganism in Children

Cofnas N. Is vegetarianism healthy for children? Crit Rev Food Sci Nutr. Published ahead of print 2018 Feb 23. https://www.ncbi.nlm.nih.gov/pubmed/29405739 .

Vegetarianism and veganism pose serious risks to brain and body development in children. Regular supplementation with iron, zinc, and B12 may not mitigate these risks. Dagnelie PC, van Staveren WA. Macrobiotic nutrition and child health: results of a population-based, mixed-longitudinal cohort study in The Netherlands. Am J Clin Nutr. 1994;59(5 Suppl):1187S–1196S. https://www.ncbi.nlm.nih.gov/pubmed/8172122 .

Children raised on a vegan (macrobiotic) diet experience retarded growth, fat and muscle wasting, slowed psychomotor development, and deficiencies of energy, protein, B12, vitamin D, calcium, and riboflavin. Von Schenck U, Bender-Götze C, Koletzko B. Persistence of neurological damage induced by dietary vitamin B-12 deficiency in infancy. Arch Dis Child. 1997;77:137–139. https://adc.bmj.com/content/77/2/137.citation-tools .

In this case study, an infant born to a vegan mom suffered from persistent neurological damage due to maternal vitamin B12 deficiency. Hudson P, Buckley R. Vegetarian diets. Are they good for pregnant women and their babies? Pract Midwife. 2000;3(7):22–23. https://www.ncbi.nlm.nih.gov/pubmed/12026434?dopt=Abstract .

A low sex ratio in newborns is an indicator of environmental stressors such as malnutrition. The normal male/female sex ratio is 105/100. This study of 6,000 women at a British hospital found a decreased sex ratio (81.5/100 vs 106/100) in vegetarians vs omnivores. This suggests that vegetarians may be malnourished, contributing to the decreased sex ratio. Guez S, Chiarelli G, Menni F, Salera S, Principi N, Esposito S. Severe vitamin B12 deficiency in an exclusively breastfed 5-month-old Italian infant born to a mother receiving supplementation during pregnancy. BMC Pediatr. 2012;12:85. https://www.ncbi.nlm.nih.gov/pubmed/22726312 .

This case study demonstrated deficiencies of B12 and iron in an infant of a vegan mother, despite maternal supplementation with a multivitamin during pregnancy. Yen CE, Yen CH, Huang MC, Cheng CH, Huang YC. Dietary intake and nutritional status of vegetarian and omnivorous preschool children and their parents in Taiwan. Nutr Res. 2008;28(7):430–436. https://www.ncbi.nlm.nih.gov/pubmed/19083442 .

Vegetarian preschoolers and parents in Taiwan have low vitamin A, calcium, and iron intake, but high intakes of vitamin C and fiber. Burdge GC, Tan SY, Henry CJ. Long-chain n-3 PUFA in vegetarian women: a metabolic perspective. J Nutr Sci. 2017;6:e58. https://www.ncbi.nlm.nih.gov/pubmed/29209497 .

EPA and DHA are lower in breastmilk and in infants of vegetarian mothers compared to omnivore mothers. Van Winckel M, Vande Velde S, De Bruyne R, Van Biervliet S. Clinical practice: vegetarian infant and child nutrition. Eur J Pediatr. 2011;170(12):1489–1494. https://www.ncbi.nlm.nih.gov/pubmed/21912895 .

The more restricted the diet of a vegetarian child or infant, the greater the risk of nutrient deficiencies. Shaikh MG, Anderson JM, Hall SK, Jackson MA. Transient neonatal hypothyroidism due to a maternal vegan diet. J Pediatr Endocrinol Metab. 2003;16(1):111–113. https://www.ncbi.nlm.nih.gov/pubmed/12585349 .

A maternal vegan diet can cause transient neonatal hypothyroidism. This may be due to low levels of iodine and other nutrients critical for thyroid function (such as selenium) in vegan diets. Yeliosof O, Silverman LA. Veganism as a cause of iodine deficient hypothyroidism. J Pediatr Endocrinol Metab. 2018;31(1):91–94. https://www.ncbi.nlm.nih.gov/pubmed/29303778 .

In this case study, a 23-month-old child developed iodine deficiency hypothyroidism due to a vegan diet.

Dietary Cholesterol, Eggs, and Heart Disease

Alexander DD, Miller PE, Vargas AJ, Weed DL, Cohen SS. Meta-analysis of egg consumption and risk of coronary heart disease and stroke. J Am Coll Nutr. 2016;35(8):704–716. https://www.ncbi.nlm.nih.gov/pubmed/27710205 .

This meta-analysis of studies assesses egg intake (a major source of dietary cholesterol) and risk of coronary heart disease (CHD) and stroke. The researchers found that an intake of one egg per day significantly decreased the risk of stroke (by 12 percent). Furthermore, daily egg intake was not associated with an increased risk of coronary heart disease. The beneficial effects of egg intake on stroke risk may be attributed to their excellent nutrient profile, including bioavailable protein, essential fatty acids, antioxidants, choline, vitamins, and minerals.

Red Meat and Cancer

Alexander DD, Weed DL, Cushing CA, Lowe KA. Meta-analysis of prospective studies of red meat consumption and colorectal cancer. Eur J Cancer Prev. 2011;20(4):293–307. https://www.ncbi.nlm.nih.gov/pubmed/21540747 .

A 2011 meta-analysis of 34 prospective studies on red meat and colorectal cancer concluded that the available data was insufficient to support an association between red meat intake and colorectal cancer. Bernstein AM, Song M, Zhang X, Pan A, Wang M, Fuchs CS, Le N, Chan AT, Willett WC, Ogino S, et al. Processed and unprocessed red meat and risk of colorectal cancer: analysis by tumor location and modification by time. PLoS One. 2015;10(8):e0135959. https://www.ncbi.nlm.nih.gov/pubmed/26305323 .

A 2015 meta-analysis found that processed red meat was linked with colorectal cancer but that unprocessed red meat was not. Alexander DD, Cushing CA. Red meat and colorectal cancer: a critical summary of prospective epidemiologic studies. Obes Rev. 2011;12(5):e472–e493. https://www.ncbi.nlm.nih.gov/pubmed/20663065 .

Some studies suggest a decrease in cancer rates in people who ate the most red meat. This finding goes to show that there is not a direct relationship between red meat intake and colorectal cancer, despite what the media and the conventional medical establishment have led us to believe.

Red Meat and Heart Disease

Micha R, Wallace SK, Mozaffarian D. Red and processed meat consumption and risk of incident coronary heart disease, stroke, and diabetes: a systematic review and meta-analysis. Circulation. 2010;121(21):2271–2283. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2885952/ .

This meta-analysis that included more than 1.2 million participants found no association between the consumption of fresh, unprocessed red meat and the risk of coronary heart disease (CHD), stroke, or diabetes. Lippi G, Mattiuzzi C, Sanchis-Gomar F. Red meat consumption and ischemic heart disease. A systematic literature review. Meat Sci. 2015;108:32–36. https://www.ncbi.nlm.nih.gov/pubmed/26017245 .

This meta-analysis of 11 studies concluded that the scientific literature does not support the existence of a relationship between red meat intake and an increased risk of myocardial ischemia. Abete I, Romaguera D, Vieira AR, Lopez de Munain A, Norat T. Association between total, processed, red and white meat consumption and all-cause, CVD, and IHD mortality: a meta-analysis of cohort studies. Br J Nutr. 2014;112(5):762–775. https://www.ncbi.nlm.nih.gov/pubmed/24932617 .

This meta-analysis of 13 studies found a positive but weak association between red meat intake and cardiovascular disease mortality. However, the authors caution that the results should be taken with a grain of salt because of the high heterogeneity of the studies included and the possibility of residual confounding. Romano KA, Martinez-Del Campo A, Kasahara K, Chittim CL, Vivas EI, Amador-Noguez D, Balskus EP, Rey FE. Metabolic, epigenetic, and transgenerational effects of gut bacterial choline consumption. Cell Host Microbe. 2017;22(3):279–290. https://www.ncbi.nlm.nih.gov/pubmed/28844887 .

Endogenous production of TMAO, a metabolite of consumed meat that is associated with heart disease, is higher in mice with greater numbers of choline-metabolizing bacteria than in mice colonized primarily with non-choline-metabolizing bacteria. This finding indicates that the composition of the gut microbiota has much to do with an individual’s TMAO level and that meat consumption may thus not be the determining factor of one’s TMAO level. Stremmel W, Schmidt KV, Schuhmann V, Kratzer F, Garbade SF, Langhans CD, Fricker G, Okun JG. Blood trimethylamine-N-oxide originates from microbiota mediated breakdown of phosphatidylcholine and absorption from small intestine. PLoS One. 2017;12(1):e0170742. https://www.ncbi.nlm.nih.gov/pubmed/28129384 .

TMA, a byproduct of the decomposition of TMAO, is only absorbed in the small intestine. Furthermore, rifaximin, the antibiotic most commonly used to treat small intestinal bacterial overgrowth (SIBO), can reduce serum levels of TMAO. These findings suggest that small intestinal bacterial overgrowth may play an important role in production and toxicity of TMAO and thus the development of cardiovascular disease. Ponziani FR, Pompili M, Di Stasio E, Zocco MA, Gasbarrini A, Flore R. Subclinical atherosclerosis is linked to small intestinal bacterial overgrowth via vitamin K2-dependent mechanisms. World J Gastroenterol. 2017;23(7):1241–1249. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5323449/pdf/WJG-23-1241.pdf .

This research indicates that atherosclerosis is linked to small intestinal bacterial overgrowth (SIBO) because SIBO depletes vitamin K2, which is needed to activate matrix Gla-protein. Matrix Gla-protein plays a key role in maintaining arterial structure and function, and low matrix Gla-protein may increase the risk of arterial stiffening and atherosclerosis.

Saturated Fat and Heart Disease

Harcombe Z. US dietary guidelines: is saturated fat a nutrient of concern? Br J Sports Med. Published ahead of print 2018 Aug 14. https://bjsm.bmj.com/content/early/2018/08/14/bjsports-2018-099420 .

An overwhelming body of scientific evidence indicates that there is no relationship between saturated fat consumption and cardiovascular disease (CVD) outcomes in adults. Robust meta-analyses also indicate a lack of relationship between saturated fat consumption and total mortality, CVD mortality, fatal myocardial infarctions, nonfatal myocardial infarctions, coronary heart disease (CHD) mortality, and CHD events. Harcombe Z, Baker JS, Cooper SM, Davies B, Sculthorpe N, DiNicolantonio JJ, Grace F. Evidence from randomised controlled trials did not support the introduction of dietary fat guidelines in 1977 and 1983: a systematic review and meta-analysis. Open Heart. 2015;2:e000196. https://openheart.bmj.com/content/2/1/e000196 .

In this systematic review and meta-analysis of RCTs examining the relationship between dietary fat, serum cholesterol, and the development of coronary heart disease, the researchers found no differences in all-cause mortality and nonsignificant differences in coronary heart disease (CHD) between groups that underwent dietary interventions intended to reduce fat and cholesterol intake and control groups. Reductions in serum cholesterol experienced by subjects in the intervention groups did not reduce CHD or all-cause mortality. This research indicates that government recommendations to limit dietary fat intake to lower cholesterol are unsupported by randomized controlled trials. Harcombe Z, Baker JS, DiNicolantonio JJ, Grace F, Davies B. Evidence from randomized controlled trials does not support current dietary fat guidelines: a systematic review and meta-analysis. Open Heart. 2016;3(2):e000409. https://www.ncbi.nlm.nih.gov/pubmed/27547428 .

Currently available randomized controlled trials do not demonstrate a significant difference in all-cause mortality or CHD mortality resulting from interventions that reduce dietary fat intake. RCT evidence does not support current governmental dietary fat guidelines. Harcombe Z, Baker JS, Davies B. Evidence from prospective cohort studies did not support the introduction of dietary fat guidelines in 1977 and 1983: a systematic review. Br J Sports Med. 2017;51(24):1737–1742. https://www.ncbi.nlm.nih.gov/pubmed/27357514 .

Epidemiological evidence available on the relationship between dietary fat and coronary heart disease (CHD) at the time US dietary guidelines were created was scant and only included six studies. Of these studies, only one found a correlation between dietary saturated fat intake and CHD deaths. None of the studies found a significant relationship between CHD deaths and saturated dietary fat in the same population. Chowdhury R, Warnakula S, Kunutsor S, Crowe F, Ward HA, Johnson L, Franco OH, Butterworth AS, Forouhi NG, Thompson SG, et al. Association of dietary, circulating, and supplement fatty acids with coronary risk: a systematic review and meta-analysis. Ann Intern Med. 2014;160(6):398–406. https://www.ncbi.nlm.nih.gov/pubmed/24723079 .

There is no relationship between dietary fatty acid intake, individual circulating fatty acids, and coronary heart disease. This evidence does not support guidelines advising people to increase their polyunsaturated fatty acid intake and decrease their saturated fat intake to reduce their risk of CHD. Mozaffarian D, Micha R, Wallace S. Effects on coronary heart disease of increasing polyunsaturated fat in place of saturated fat: a systematic review and meta-analysis of randomized controlled trials. PLoS Med. 2010;7(3):e1000252. https://www.ncbi.nlm.nih.gov/pubmed/20351774 .

While this study showed benefits by replacing dietary saturated fat with polyunsaturated fat, it excluded two studies that would have changed the results and also included non-randomized non-controlled studies. Guyenet S. Does dietary saturated fat increase blood cholesterol? An informal review of observational studies. Whole Health Source. 2011 Jan 13. http://wholehealthsource.blogspot.com/2011/01/does-dietary-saturated-fat-increase.htm .

There are several long-term RCTs that indicate that saturated fat intake raises blood cholesterol, but the associations are weak. Yusuf S, Hawken S, Ounpuu S, Dans T, Avezum A, Lanas F, McQueen M, Budaj A, Pais P, Varigos J, et al. Effect of potentially modifiable risk factors associated with myocardial infarction in 52 countries (the INTERHEART study): case-control study. Lancet. 2004;364(9438):937–952. https://www.ncbi.nlm.nih.gov/pubmed/15364185 .

Modifiable diet and lifestyle factors account for 90 percent of cardiovascular disease worldwide. Davidson MH, Ballantyne CM, Jacobson TA, Bittner VA, Braun LT, Brown AS, Brown WV, Cromwell WC, Goldberg RB, McKenney JM, et al. Clinical utility of inflammatory markers and advanced lipoprotein testing: advice from an expert panel of lipid specialists. J Clin Lipidol. 2011;5(5):338–367. https://www.ncbi.nlm.nih.gov/pubmed/21981835 .

LDL particle number is a better predictor of heart disease risk than total cholesterol or LDL cholesterol. Often when LDL is high, LDL particle number is also high, but it is possible to have normal or low cholesterol and a high LDL particle number; in fact, this pattern is common in people with metabolic syndrome and type 2 diabetes. Koskinen J, Magnussen CG, Würtz P, Soininen P, Kangas AJ, Viikari JS, Kähönen M, Loo BM, Jula A, Ahotupa M, et al. Apolipoprotein B, oxidized low-density lipoprotein, and LDL particle size in predicting the incidence of metabolic syndrome: the Cardiovascular Risk in Young Finns study. Eur J Prev Cardiol. 2012;19(6):1296–1303. https://www.ncbi.nlm.nih.gov/pubmed/21960651 .

Metabolic syndrome may be a cause of increased LDL particle number. It is not clear which comes first, the increased LDL-P or metabolic syndrome, but it is likely that they influence each other bidirectionally. Newman D. Statins given for 5 years for heart disease prevention (with known heart disease). The NNT. 2013 Nov 2. http://www.thennt.com/nnt/statins-for-heart-disease-prevention-with-known-heart-disease/ .

While statins are effective in reducing the risk of heart attacks and heart disease in people who already have heart disease, 83 people have to be treated to extend one life, and 39 have to be treated to prevent one repeat heart attack. Gutierrez J, Ramirez G, Rundek T, Sacco RL. Statin therapy in the prevention of recurrent cardiovascular events: a sex-based meta-analysis. Arch Intern Med. 2012;172(12):909–919. https://www.ncbi.nlm.nih.gov/pubmed/22732744 .

Statin therapy has no benefit on stroke incidence or all-cause mortality in women. Ray KK, Seshasai SR, Ergou S, Sever P, Jukema JW, Ford I, Sattar N. Statins and all-cause mortality in high-risk primary prevention: a meta-analysis of 11 randomized controlled trials involving 65,229 participants. Arch Intern Med. 2010;170(12):1024–1031. https://www.ncbi.nlm.nih.gov/pubmed/20585067 .

This large meta-analysis of 11 RCTs showed that statins didn’t reduce all-cause mortality in people without preexisting heart disease.

Acid–Alkaline Myth

Fenton TR, Lyon AW, Eliasziw M, Tough SC, Hanley DA. Meta-analysis of the effect of the acid-ash hypothesis of osteoporosis on calcium balance. J Bone Min Res. 2009;24(11):1835–1840. https://onlinelibrary.wiley.com/doi/full/10.1359/jbmr.090515 .

Clinical trials do not support the acid–ash hypothesis of osteoporosis, in which “acidic” foods in the diet are purported to have a negative effect on calcium metabolism. Promotion of an “alkaline” diet to prevent calcium loss is not justified by the literature. Fenton TR, Tough SC, Lyon AW, Eliasziw M, Hanley DA. Causal assessment of dietary acid load and bone disease: a systematic review & meta-analysis applying Hill’s epidemiologic criteria for causality. Nutr J. 2011;10:41. https://www.ncbi.nlm.nih.gov/pubmed/21529374 .

This systematic review concludes that a causal relationship between dietary acid load and osteoporotic bone disease is not supported by scientific evidence and that the alkaline diet is unlikely to be protective of bone health. Bonjour JP. Nutritional disturbance in acid-base balance and osteoporosis: a hypothesis that disregards the essential homeostatic role of the kidney. Br J Nutr. 2013;110(7):1168–1177. https://www.ncbi.nlm.nih.gov/pubmed/23551968 .

Acid–base balance is tightly regulated in the body with the help of the kidneys. There is no evidence to support the hypothesis that a diet high in “acidic” foods, such as animal foods, increases the risk of osteoporosis by upsetting acid–base balance. McLean RR, Qiao N, Broe KE, Tucker KL, Casey V, Cupples LA, Kiel DP, Hannan MT. Dietary acid load is not associated with lower bone mineral density except in older men. J Nutr. 2011;141(4):588–594. https://academic.oup.com/jn/article/141/4/588/4630600 .

Observational studies do not support the acid–ash hypothesis of osteoporosis. Dietary acid load is not associated with depreciations in bone mineral density. Fenton TR, Eliasziw M, Tough SC, Lyon AW, Brown JP, Hanley DA. Low urine pH and acid excretion do not predict bone fractures or the loss of bone mineral density: a prospective cohort study. BMC Musculoskel Dis. 2010;11:88. https://bmcmusculoskeletdisord.biomedcentral.com/articles/10.1186/1471-2474-11-88#Decs .

In this observational study, low urine pH and urinary acid excretion were not predictive of bone fractures or loss of bone mineral density. Pedone C, Napoli N, Pozzilli P, Lauretani F, Bandinelli S, Ferrucci L, Antonelli-Incalzi R. Quality of diet and potential renal acid load as risk factors for reduced bone density in elderly women. Bone. 2010;46(4):1063–1067. https://www.ncbi.nlm.nih.gov/pubmed/20005315 .

There is no association between dietary acid load and trabecular and cortical bone mineral density in women aged 60 years and older. Tucker KL, Hannan MT, Kiel DP. The acid-base hypothesis: diet and bone in the Framingham Osteoporosis Study. Eur J Nutr. 2001;40(5):231–237. https://www.ncbi.nlm.nih.gov/pubmed/11842948 .

Higher, rather than lower, protein intakes are associated with reduced bone loss, in the context of a diet that contains ample fruits and vegetables. Munger RG, Cerhan JR, Chiu BC. Prospective study of dietary protein intake and risk of hip fracture in postmenopausal women. Am J Clin Nutr. 1999;69(1):147–152. https://www.ncbi.nlm.nih.gov/pubmed/9925137?dopt=Abstract .

A sufficient intake of dietary protein, especially from animal sources, is associated with a reduced risk of hip bone fractures in postmenopausal women.

Dairy Products

Kratz M, Baars T, Guyenet S. The relationship between high-fat dairy consumption and obesity, cardiovascular, and metabolic disease. Eur J Nutr. 2013;52(1):1–24. https://www.ncbi.nlm.nih.gov/pubmed/22810464 .

Observational studies do not support the existence of a relationship between the consumption of dairy fat or high-fat dairy foods and an increased risk of cardiometabolic disease or obesity. In fact, the consumption of high-fat dairy is inversely associated with obesity risk. This may be due to the presence of specific bioactive compounds in full-fat dairy, such as conjugated linoleic acid (CLA) and butyric acid. Drehmer M, Pereira MA, Schmidt MI, Alvim S, Lotufo PA, Luft VC, Duncan BB. Total and full-fat, but not low-fat, dairy product intakes are inversely associated with metabolic syndrome in adults. J Nutr. 2016;146(1):81–89. https://www.ncbi.nlm.nih.gov/pubmed/26511614 .

The consumption of full-fat dairy products is inversely associated with metabolic syndrome in middle-aged and older adults. Dietary recommendations to avoid full-fat dairy products are not supported by the scientific literature. De Oliveira Otto MC, Lemaitre RN, Song X, King IB, Siscovick DS, Mozaffarian D. Serial measures of circulating biomarkers of dairy fat and total and cause-specific mortality in older adults: the Cardiovascular Health Study. Am J Clin Nutr. Published ahead of print 2018 Jul 11. https://www.ncbi.nlm.nih.gov/pubmed/30007304 .

Long-term exposure to dairy fats is not significantly associated with total mortality or incident cardiovascular disease and stroke in adults. In fact, high circulating levels of heptadecanoic acid, a dairy fat, are inversely associated with cardiovascular disease and stroke mortality. The study of biomarkers of dairy fat consumption provide more objective insight into the impact of long-term exposure to dairy fats on health than the more commonly used self-reported consumption. Liang J, Zhou Q, Kwame Amakye W, Su Y, Zhang Z. Biomarkers of dairy fat intake and risk of cardiovascular disease: a systematic review and meta analysis of prospective studies. Crit Rev Food Sci Nutr. 2018;58(7):1122–1130. https://www.ncbi.nlm.nih.gov/pubmed/28001085 .

This systematic review and meta-analysis of 13 studies involving 7,680 subjects found that higher dairy fat exposure is not associated with an increased risk of cardiovascular disease. Appleby P, Roddam A, Allen N, Key T. Comparative fracture risk in vegetarians and nonvegetarians in EPIC-Oxford. Eur J Clin Nutr. 2007;61:1400–1406. https://www.nature.com/articles/1602659 .

Vegans have a higher fracture risk than meat eaters, fish eaters, and vegetarians. This may be due in part to their significantly lower calcium intake. Bian S, Hu J, Zhang K, Wang Y, Miaohui Y, Ma J. Dairy product consumption and risk of hip fracture: a systematic review and meta-analysis. BMC Public Health. 2018;18:165. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5778815/ .

This systematic review and meta-analysis indicates that the consumption of dairy products, specifically yogurt and cheese, is associated with a lower risk of hip fracture.

The Problem with Nutrition Research

Ioannidis JPA. The challenge of reforming nutritional epidemiologic research. JAMA. 2018;320(10):969–970. https://jamanetwork.com/journals/jama/article-abstract/2698337 .

Epidemiological studies assessing nutritional factors and health outcomes are often used to draw conclusions about causality when, in reality, the conclusions are spurious. It is nearly impossible to disentangle the impact of a single dietary influence on health. Nutritional epidemiological research is also notoriously biased.

Longevity of Meat Eaters versus Vegetarians and Vegans

Key TJ, Thorogood M, Appleby PN, Burr ML. Dietary habits and mortality in 11,000 vegetarians and health conscious people: results of a 17 year follow up. BMJ. 1996;313(7060):775–779. https://www.ncbi.nlm.nih.gov/pubmed/8842068 .

This study assessed the relationship between dietary habits and mortality in vegetarians and omnivores who frequented health-food stores, based on the premise that health-food store shoppers would be more health-conscious, regardless of whether or not they ate meat. It was found that both vegetarians and health-conscious omnivores live longer than people in the general population and that there was no survival difference between vegetarians and omnivores. Key TJ, Appleby PN, Spencer EA, Travis RC, Roddam AW, Allen NE. Mortality in British vegetarians: results from the European Prospective Investigation into Cancer and Nutrition (EPIC-Oxford). Am J Clin Nutr. 2009;89(5):1613S–1619S. https://academic.oup.com/ajcn/article/89/5/1613S/4596950 .

In this study, vegetarians and their omnivorous friends and family (who were recruited with the assumption that they would be more health conscious than the general population) were followed for five to 10 years. The risk of death for vegetarians/vegans and health-conscious omnivores was 52 percent lower than the risk of death for the general population. There was no difference in mortality between vegetarians and omnivores. Chang-Claude J, Hermann S, Eilber U, Steindorf K. Lifestyle determinants and mortality in German vegetarians and health-conscious persons: results of a 21-year follow-up. Cancer Epidemiol Biomarkers Prev. 2005; 14(4):963–968. http://cebp.aacrjournals.org/content/14/4/963.long .

The Heidelberg Study in Germany compared lifespan in health-conscious omnivores with vegetarians (a total of 2,000 participants). The risk of death for both vegetarians/vegans and omnivores was 59 percent lower than the risk of death for the general population. They found no difference in mortality between vegetarians and omnivores. The study found that a high level of physical activity was the greatest predictor of lifespan—independently of whether meat was consumed. Mihrshahi S, Ding D, Gale J, Allman-Farinelli M, Banks E, Bauman AE. Vegetarian diet and all-cause mortality: evidence from a large population-based Australian cohort – the 45 and Up Study. Prev Med. 2017;97:1–7. https://www.ncbi.nlm.nih.gov/pubmed/28040519 .

This study, which did a good job of controlling for confounding factors, found no evidence that a vegetarian, semi-vegetarian, or pesco-vegetarian diet had a protective effect on all-cause mortality. Kwok CS, Umar S, Myint PK, Mamas MA, Loke YK. Vegetarian diet, Seventh Day Adventists and risk of cardiovascular mortality: a systematic review and meta-analysis. Int J Cardiol. 2014;176(3):680–686. https://www.sciencedirect.com/science/article/pii/S016752731401290X .

A meta-analysis of studies comparing mortality in vegetarians/vegans and omnivores found no mortality benefit for vegetarians/vegans. It also concluded that any previous observed benefits were driven by Seventh Day Adventist studies, which are plagued with confounding variables.

Low-Carb and Ketogenic Diets

Virta Health: Clinical Outcomes of Low-Carb Diets

Public Health Collaboration: Review Comparing Low-Carb and Low-Fat Diets

Vazquez JA, Adibi SA. Protein sparing during treatment of obesity: ketogenic versus nonketogenic very low calorie diet. Metabolism. 1992;41(4):406–414. https://www.ncbi.nlm.nih.gov/pubmed/1556948 .

When protein intake is held constant, a nonketogenic very-low-calorie diet is superior to a ketogenic diet for sparing body protein. A nonketogenic very-low-calorie diet may be best for preventing loss of lean body mass during weight reduction efforts. Willi SM, Oexmann MJ, Wright NM, Collop NA, Key LL Jr. The effects of a high-protein, low-fat, ketogenic diet on adolescents with morbid obesity: body composition, blood chemistries, and sleep abnormalities. Pediatrics. 1998;101(1 Pt 1):61–67. https://www.ncbi.nlm.nih.gov/pubmed/9417152 .

In adolescents with morbid obesity, a ketogenic diet induced rapid weight loss of predominantly fat tissue with minimal effects on lean body mass. Serum cholesterol and the prevalence of sleep abnormalities also decreased. Volek JS, Sharman MJ, Love DM, Avery NG, Gómez AL, Scheett TP, Kraemer WJ. Body composition and hormonal responses to a carbohydrate-restricted diet. Metabolism. 2002;51(7):864–870. https://www.ncbi.nlm.nih.gov/pubmed/12077732 .

In this study, 12 healthy men switched from a diet containing 48 percent carbohydrate to one containing 8 percent carbohydrate for six weeks. By week six, fat mass had significantly decreased, whereas lean body mass increased. The subjects also experienced decreases in insulin and increases in total thyroxine and free T4. Volek JS, Sharman MJ, Gómez AL, Judelson DA, Rubin MR, Watson G, Sokmen B, Silvestre R, French DN, Kraemer WJ. Comparison of energy-restricted very low-carbohydrate and low-fat diets on weight loss and body composition in overweight men and women. Nutr Metab (Lond). 2004;1:13. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC538279/ .

A very-low-carbohydrate ketogenic diet (VLCK) was superior to a low-fat diet for inducing rapid body weight and fat loss. The subjects experienced a preferential loss of trunk fat (fat in the abdominal area), which is associated with insulin resistance, dyslipidemia, diabetes, and atherosclerosis. Dansinger ML, Gleason JA, Griffith JL, Selker HP, Schaefer EJ. Comparison of the Atkins, Ornish, Weight Watchers, and Zone diets for weight loss and heart disease risk reduction: a randomized trial. JAMA. 2005;293(1):43–53. https://jamanetwork.com/journals/jama/fullarticle/200094 .

In this study, 160 participants were assigned to either an Atkins (low-carb), Zone (balanced macronutrient), Weight Watchers (low-calorie), or Ornish (low-fat) diet group. All participants lost weight and experienced reductions in total/HDL cholesterol, C-reactive protein, and insulin. However, compliance was best in the Atkins, Zone, and Weight Watchers groups. Johnston CS, Tjonn SL, Swan PD, White A, Hutchins H, Sears B. Ketogenic low-carbohydrate diets have no metabolic advantage over nonketogenic low-carbohydrate diets. Am J Clin Nutr. 2006;83(5):1055–1061. https://academic.oup.com/ajcn/article/83/5/1055/4649481 .

Ketogenic and non-ketogenic low-carbohydrate diets were equally effective in reducing body weight and insulin resistance in sedentary, overweight men and women. However, the arachidonic acid/EPA ratio was higher and perceptions of physical vigor were lower in the ketogenic diet subjects. Layman DK, Evans E, Baum JI, Seyler J, Erickson DJ, Boileau RA. Dietary protein and exercise have additive effects on body composition during weight loss in adult women. J Nutr. 2005;135(8):1903–1910. https://academic.oup.com/jn/article/135/8/1903/4663944 .

Subjects on a high-protein, low-carbohydrate diet lost more total weight and fat mass, preserved more lean mass, and experienced greater reductions in triglycerides and maintained higher HDL cholesterol than subjects on a low-protein, high-carbohydrate diet. Johnstone AM, Horgan GW, Murison SD, Bremner DM, Lobley GE. Effects of a high-protein, ketogenic diet on hunger, appetite, and weight loss in obese men feeding ad libitum. Am J Clin Nutr. 2008;87(1):44–55. https://www.ncbi.nlm.nih.gov/pubmed/18175736 .

In 17 obese men, a high-protein, low-carbohydrate ketogenic diet reduced hunger and food intake significantly more than a high-protein, medium-carbohydrate, non-ketogenic diet. Sacks FM, Bray GA, Carey VJ, Smith SR, Ryan DH, Anton SD, McManus K, Champagne CM, Bishop LM, Laranjo N, et al. Comparison of weight-loss diets with different compositions of fat, protein, and carbohydrates. N Engl J Med. 2009;360(9):859–873. https://www.ncbi.nlm.nih.gov/pubmed/19246357 .

Reduced-calorie diets produce weight loss regardless of the type of macronutrient that is restricted. Weight loss was similar between subjects consuming diets with 40 percent fat, 25 percent protein, and 35 percent carbohydrate; 40 percent fat, 15 percent protein, and 45 percent carbohydrate; 20 percent fat, 25 percent protein, and 55 percent carbohydrate; or 20 percent fat, 15 percent protein, and 65 percent carbohydrate. Jabekk PT, Moe IA, Meen HD, Tomten SE, Høstmark AT. Resistance training in overweight women on a ketogenic diet conserved lean body mass while reducing body fat. Nutr Metab (Lond). 2010;7:17. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2845587/ .

In 18 untrained women, a ketogenic diet combined with resistance training significantly reduced body fat without altering lean body mass. Ebbeling CB, Swain JF, Feldman HA, Wong WW, Hachey DL, Garcia-Lago E, Ludwig DS. Effects of dietary composition on energy expenditure during weight-loss maintenance. JAMA. 2012;307(24):2627–2634. https://www.ncbi.nlm.nih.gov/pubmed/22735432 .

During weight loss maintenance, resting energy expenditure (REE) and total energy expenditure (TEE) are reduced more in people on a low-fat diet than in people on a very-low-carbohydrate diet. This may make it hard for people on low-fat diets to maintain their weight loss over the long term. Wood RJ, Gregory SM, Sawyer J, Milch CM, Matthews TD, Headley SA. Preservation of fat-free mass after two distinct weight loss diets with and without progressive resistance exercise. Metab Syndr Relat Disord. 2012;10(3):167–174. https://www.ncbi.nlm.nih.gov/pubmed/22283635 .

Low-fat and low-carb diets with and without progressive resistance exercise all promote weight loss, but low-carb diets produce greater improvements in triglyceride and HDL levels. Paoli A, Grimaldi K, D’Agostino D, Cenci L, Moro T, Bianco A, Palma A. Ketogenic diet does not affect strength performance in elite artistic gymnasts. J Int Soc Sports Nutr. 2012;9:34. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3411406/ .

The ketogenic diet is capable of producing significant decreases in body weight and fat over a short period of time (30 days) without adversely impacting strength performance in gymnastic athletes. Ruth MR, Port AM, Shah M, Bourland AC, Istfan NW, Nelson KP, Gokce N, Apovian CM. Consuming a hypocaloric high fat low carbohydrate diet for 12 weeks lowers C-reactive protein, and raises serum adiponectin and high density lipoprotein-cholesterol in obese subjects. Metabolism. 2013;62(12):1779–1787. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3845365/ .

C-reactive protein decreased and serum adiponectin and HDL cholesterol increased significantly in obese adults on a low-carb, high-fat diet (HFLC) compared to those on a low-fat, high-carb diet (LFHC). This suggests that an HFLC diet is better for improving cardiovascular health and inflammation than an LFHC diet. Rhyu H, Cho S-Y. The effect of weight loss by ketogenic diet on the body composition, performance-related physical fitness factors and cytokines of Taekwondo athletes. J Exerc Rehabil. 2014;10(5): 326–331. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4237850/ .

A ketogenic diet significantly reduced sprint time, fatigue, and TNF-⍺ in Taekwondo athletes. Non-ketogenic athletes did not experience these beneficial effects. These findings suggest that a ketogenic diet improves aerobic capacity and fatigue resistance and has an anti-inflammatory response. Rauch JT, Silva JE, Lowery RP, McCleary SA, Shields KA, Ormes JA, Sharp MH, Weiner SI, Georges JI, Volek JS, et al. The effects of ketogenic dieting on skeletal muscle and fat mass. J Int Soc Sports Nutr. 2014;11(Suppl 1):P40. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4271639/ .

In college-age resistance-trained males, a very-low-carbohydrate ketogenic diet (VLCKD) containing 5 percent carbohydrate significantly increased lean body mass and decreased fat mass compared to a standard Western diet containing 55 percent carbohydrate. Bazzano LA, Hu T, Reynolds K, Yao L, Bunol C, Liu Y, Chen C-S, Klag MJ, Whelton PK, He J. Effects of low-carbohydrate and low-fat diets: a randomized trial. Ann Intern Med. 2014;161(5):309–318. http://annals.org/aim/article-abstract/1900694/effects-low-carbohydrate-low-fat-diets-randomized-trial .

In men and women with cardiovascular disease and diabetes, a low-carbohydrate diet is more effective for weight loss and cardiovascular disease risk factor reduction than a low-fat diet. Hall KD, Bemis T, Brychta R, Chen KY, Courville A, Crayner EJ, Goodwin S, Guo J, Howard L, Knuth ND, et al. Calorie for calorie, dietary fat restriction results in more body fat loss than carbohydrate restriction in people with obesity. Cell Metab. 2015;22(3):427–436. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4603544/ .

This very short-term (six days long) study demonstrated that dietary fat restriction led to a greater body fat loss in obese adults than carb restriction. However, carb intake on the low-carb diet was around 140 grams per day, which is not really low-carb at all. The researchers also chose a method of assessing fat loss that presents some problems: to quantify net fat loss, they measured the difference between fat intake and fat oxidation in the low-carb and low-fat diet groups. This is not the most accurate reflection of fat loss because fat oxidation can be very high on a low-carb diet, but if fat intake is also high, as is typical with low-carb diets, the “net fat loss” will be small. Conversely, low fat oxidation combined with a low fat intake (the low-fat group) could potentially demonstrate a larger net fat loss despite no significant increase in fat oxidation. Upon further examination, it becomes clear that the low-carb diet produced greater fat oxidation and fat loss, despite the fact that net fat loss was smaller. Hall KD, Chen KY, Guo J, Lam YY, Leibel RL, Mayer LE, Reitman ML, Rosenbaum M, Smith SR, Walsh BT, et al. Energy expenditure and body composition changes after an isocaloric ketogenic diet in overweight and obese men. Am J Clin Nutr. 2016;104(2):324–333. https://www.ncbi.nlm.nih.gov/pubmed/27385608 .

In 17 overweight and obese men, four weeks of a ketogenic diet resulted in weight and body fat loss, a slightly increased energy expenditure (EE), and a decreased respiratory quotient (RQ). The respiratory quotient is the ratio of carbon dioxide consumed by the body to oxygen consumed by the body and is used to indicate which macronutrients are being metabolized. A decrease in RQ indicates a transition from primarily carbohydrate oxidation to fat oxidation. Meirelles CM, Gomes PSC. Effects of short-term carbohydrate restrictive and conventional hypoenergetic diets and resistance training on strength gains and muscle thickness. J Sports Sci Med. 2016;15(4):578–584. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5131210/ .

In this study, the effects of carbohydrate-restricted and conventional hypocaloric diets combined with resistance training were assessed for their effects on weight loss, body fat loss, strength gains, and muscle thickness. While the differences were not deemed significant, body mass and body fat loss were greater in the carbohydrate-restricted diet group than in the conventional hypocaloric group. Total body strength increased in both groups but there were no changes in muscle thickness. Had the study period been longer, these differences might have become more pronounced. Goday A, Bellido D, Sajoux I, Crujeiras AB, Burguera B, García-Luna PP, Oleaga A, Moreno B, Casanueva FF. Short-term safety, tolerability and efficacy of a very low-calorie ketogenic diet interventional weight loss program versus hypocaloric diet in patients with type 2 diabetes mellitus. Nutr Diabetes. 2016;6(9):e230. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5048014/ .

Eighty-nine men and women with type 2 diabetes and BMIs of 30 or greater were randomly assigned to a very-low-carb ketogenic (VLCK) diet or a conventional low-calorie diet for four months. Weight loss, reductions in waist circumference and hemoglobin A1c, and improvements in glycemic control were significantly greater in the VLCK group compared to the conventional low-calorie group. Hu T, Yao L, Reynolds K, Niu T, Li S, Whelton PK, He J, Steffen LM, Bazzano LA. Adherence to low-carbohydrate and low-fat diets in relation to weight loss and cardiovascular risk factors. Obes Sci Pract. 2016;2(1):24–31. https://www.ncbi.nlm.nih.gov/pubmed/27114827 .

Though adherence to low-carb and low-fat diets is similar, a low-carb diet is associated with significant reductions in body weight and improvement of body composition while a low-fat diet is not. Veum VL, Laupsa-Borge J, Eng Ø, Rostrup E, Larsen TH, Nordrehaug JE, Nygård OK, Sagen JV, Gudbrandsen OA, Dankel SN, et al. Visceral adiposity and metabolic syndrome after very high-fat and low-fat isocaloric diets: a randomized controlled trial. Am J Clin Nutr. 2017;105(1):85–99. https://academic.oup.com/ajcn/article/105/1/85/4637481 .

Forty-six overweight men were randomized to either a very-high-fat low-carbohydrate diet (VHFLC) or a low-fat high-carbohydrate diet (LFHC). The groups experienced similar decreases in waist circumference, abdominal subcutaneous fat mass, visceral fat mass, and total body weight. They also experienced similar improvements in dyslipidemia, reductions in insulin, hemoglobin A1c, and HOMA2-IR. These findings support the idea that dietary fat does not promote ectopic obesity and cardiovascular disease in humans. Merra G, Miranda R, Barrucco S, Gualtieri P, Mazza M, Moriconi E, Marchetti M, Chang TFM, De Lorenzo A, Di Renzo L. Very-low-calorie ketogenic diet with aminoacid supplement versus very low restricted-calorie diet for preserving muscle mass during weight loss: a pilot double-blind study. Eur Rev Med Pharmacol Sci. 2016;20(12):2613–2621. https://www.europeanreview.org/article/11018 .

A very-low-carbohydrate ketogenic diet (VLCKD) supplemented with whey protein produced significant reductions in body weight compared to a very-low-restricted-calorie diet (VLRC) without causing reductions in lean body mass. Gardner CD, Offringa LC, Hartle JC, Kapphahn K, Cherin R. Weight loss on low-fat vs. low-carbohydrate diets by insulin resistance status among overweight adults and adults with obesity: a randomized pilot trial. Obesity (Silver Spring). 2016;24(1):79–86. https://www.ncbi.nlm.nih.gov/pubmed/26638192 .

Both low-fat and low-carb diets induce weight loss in overweight and obese adults, regardless of whether the individuals are insulin-sensitive or insulin-resistant. Chatterton S, Helms ER, Zinn C, Storey A. The effect of an 8-week low carbohydrate high fat (LCHF) diet in sub-elite Olympic weightlifters and powerlifters on strength, body composition, mental state and adherence: a pilot study. J Aust Strength Cond. 2017;25(2):6–13. https://www.researchgate.net/publication/316675957_The_effect_of_an_8-week_low_carbohydrate_high_fat_LCHF_diet_in_sub-elite_Olympic_weightlifters_and_powerlifters_on_strength_body_composition_mental_state_and_adherence_a_pilot_case-study .

In five sub-elite-level Olympic weightlifters and powerlifters, eight weeks of a low-carb high-fat diet produced weight loss in four out of five lifters, reduced skinfold measurements in three subjects, and increased strength in two subjects. Though the lifters found the diet acceptable for training and lifestyle, they did report low energy and fatigue as common side effects. Gregory RM, Hamdan H, Torisky DM, Akers JD. A low-carbohydrate ketogenic diet combined with 6-weeks of Crossfit training improves body composition and performance. Int J Sports Exerc Med. 2017;3(2). https://clinmedjournals.org/articles/ijsem/international-journal-of-sports-and-exercise-medicine-ijsem-3-054.php?jid=ijsem .

In 27 non-elite CrossFit subjects, six weeks of a low-carb ketogenic diet led to greater reductions in body weight, BMI, percent body fat, and fat mass than did a control diet. Urbain P, Strom L, Morawski L, Wehrle A, Deibert P, Bertz H. Impact of a 6-week non-energy-restricted ketogenic diet on physical fitness, body composition and biochemical parameters in healthy adults. Nutr Metab (Lond). 2017;14:17. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5319032/ .

Six weeks of a non-energy-restricted ketogenic diet in healthy adults resulted in weight loss and reductions in glucose, insulin, and IGF-1. However the diet also had a mild negative impact on endurance capacity, peak power, and time to exhaustion during exercise, suggesting that it may have adverse impacts on competitive athletes. Wilson JM, Lowery RP, Roberts MD, Sharp MH, Joy JM, Shields KA, Partl J, Volek JS, D’Agostino D. The effects of ketogenic dieting on body composition, strength, power, and hormonal profiles in resistance training males. J Strength Cond Res. Published ahead of print 2017 Apr 7. https://journals.lww.com/nsca-jscr/Abstract/publishahead/The_Effects_of_Ketogenic_Dieting_on_Body.96026.aspx .

In 25 college-aged resistance-trained men, both ketogenic and Western diets increased lean body mass, decreased fat mass, and increased strength and power. However, the KD increased testosterone while the WD decreased testosterone. These findings suggest that the ketogenic diet can improve body composition, physical performance, and hormonal profiles in resistance-trained men. Colica C, Merra G, Gasbarrini A, De Lorenzo A, Cioccoloni G, Gualtieri P, Perrone MA, Bernardini S, Bernardo V, Di Renzo L, et al. Efficacy and safety of very-low-calorie ketogenic diet: a double blind randomized crossover study. Eur Rev Med Pharmacol Sci. 2017;21(9):2274–2289. https://www.ncbi.nlm.nih.gov/pubmed/28537652 .

In this randomized crossover trial, two dietary treatments were used: a very-low-carbohydrate ketogenic diet in which 50 percent of protein was replaced with synthetic amino acids (VLCKD1) and a VLCKD with placebo (VLCKD2). Two weeks of a VLCKD1 reduced BMI, total body water, android fat percentage (percentage of weight around the chest and abdomen), android fat mass, gynoid fat mass (amount of fat around the hips, buttocks, and thighs), intermuscular adipose tissue, and HOMA-IR. Two weeks of VLCKD2 reduced BMI, android fat mass, gynoid fat mass, appendicular skeletal muscle mass index, and HOMA-IR. Neither diet impaired nutritional state and not significant effects were found on sarcopenia, bone mineral content, and hepatic, renal, and lipid profiles.

Meta-Analyses of Low-Carb Diets

Hession M, Rolland C, Kulkarni U, Wise A, Broom J. Systematic review of randomized controlled trials of low-carbohydrate vs. low-fat/low-calories diets in the management of obesity and its comorbidities. Obes Rev. 2009;10(1):36–50. https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1467-789X.2008.00518.x .

This systematic review found that low-carb diets were more effective at promoting weight loss, lowering triglycerides and systolic blood pressure, and raising HDL cholesterol in obese individuals over the course of six months than low-fat, low-calorie diets. The low-fat, low-calorie group also had a higher attrition rate than the low-carb group, indicating patient preference for a low-carb, high-protein approach. Castaneda-Gonzalez LM, Bacardi Gascon M, Jimenez Cruz A. Effects of low carbohydrate diets on weight and glycemic control among type 2 diabetes individuals: a systematic review of RCT greater than 12 weeks. Nutr Hosp. 2011;26(6):1270–1276. https://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0048000/ .

This systematic review analyzed randomized controlled trials examining the effects of low-carb, low-fat, low-glycemic index, and control diets on weight and glycemic control in patients with type 2 diabetes. The trials were all longer than 12 weeks in duration. Of the eight RCTs included in the review, one demonstrated significantly greater weight reduction on a low-carb diet compared to a control diet and two trials demonstrated significantly lower hemoglobin A1c on a low-carb diet. Unfortunately, the studies included in this review had some methodological weaknesses that may have obscured the true differences between low-carb and conventional diets in the treatment of type 2 diabetes: the amount of carbohydrates in the “low-carb” diets varied widely, from 19 grams to as high as 95 grams per day; the number of subjects in each study varied greatly; and only two of the eight trials included intention to treat. Nonetheless, this review suggests that low-carb diets may have some benefits over low-fat and control diets in the management of type 2 diabetes. Santos FL, Esteves SS, da Costa Pereira A, Yancy WS Jr, Nunes JPL. Systematic review and meta-analysis of clinical trials of the effects of low carbohydrate diets on cardiovascular risk factors. Obes Rev. 2012;13(11):1048–1066. https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1467-789X.2012.01021.x .

This meta-analysis of data from 1,141 obese individuals indicates that a low-carb diet is associated with significant decreases in body weight, BMI, abdominal circumference, systolic and diastolic blood pressure, triglycerides, fasting glucose, hemoglobin A1c, insulin, and C-reactive protein and increases in HDL cholesterol. These findings indicate that low-carb diets are beneficial for reducing cardiovascular disease risk factors. Bezerra Bueno N, Vieira de Melo IS, Lima de Oliveira S, da Rocha Ataide T. Very-low-carbohydrate diet v. low-fat diet for long-term weight loss: a meta-analysis of randomised controlled trials. Br J Nutr. 2013;110(7):1178–1187. https://www.cambridge.org/core/journals/british-journal-of-nutrition/article/verylowcarbohydrate-ketogenic-diet-v-lowfat-diet-for-longterm-weight-loss-a-metaanalysis-of-randomised-controlled-trials/6FD9F975BAFF1D46F84C8BA9CE860783 .

In this meta-analysis comparing studies of very-low-carbohydrate ketogenic diets (VLCKD) with low-fat diets for weight loss, patients assigned to VLCKD experienced greater weight loss, decreases in triglycerides and diastolic blood pressure, and increased HDL cholesterol compared to patients assigned to a low-fat diet. Sackner-Bernstein J, Kanter D, Kaul S. Dietary intervention for overweight and obese adults: Comparison of low-carbohydrate and low-fat diets. A meta-analysis. PLoS One. 2015;10(10):e0139817. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0139817 .

While both low-carb and low-fat diets demonstrated beneficial effects on weight loss in this meta-analysis, low-carb diets were associated with significantly greater weight loss and improvements in risk factors for atherosclerosis and cardiovascular disease. Tobias DK, Chen M, Manson JE, Ludwig DS, Willett W, Hu FB. Effect of low-fat diet interventions versus other diet interventions on long-term weight change in adults: a systematic review and meta-analysis. Lancet Diabetes Endocrinol. 2015;3(12):968–979. https://www.ncbi.nlm.nih.gov/pubmed/26527511 .

In weight loss trials, low-carbohydrate diets produced significantly greater weight loss than low-fat diet interventions. Evidence from randomized controlled trials thus does not support the use of low-fat diets over low-carb diets for long-term weight loss. Mansoor N, Vinknes KJ, Veierød MB, Retterstøl K. Effects of low-carbohydrate diets v. low-fat diets on body weight and cardiovascular risk factors: a meta-analysis of randomised controlled trials. Br J Nutr. 2016;115(Suppl 3):466–479. https://www.cambridge.org/core/journals/british-journal-of-nutrition/article/effects-of-lowcarbohydrate-diets-v-lowfat-diets-on-body-weight-and-cardiovascular-risk-factors-a-metaanalysis-of-randomised-controlled-trials/B8FBAC51C156D8CAB189CF0B14FB2A46 .

Compared to participants on low-fat diets, participants on low-carb diets (carbs comprising less than 20 percent of total energy intake) experienced greater decreases in body weight and triglycerides and greater increases in HDL and LDL cholesterol. While decreased body weight and triglycerides and increased HDL are associated with reduced cardiovascular disease risk, elevated LDL has typically been associated with increased risk; however, new research indicates that it is LDL particle number, rather than total LDL itself, that is a predictor of heart disease. These findings thus suggest that low-carb diets have beneficial effects on several key cardiovascular disease risk factors. Fan Y, Di H, Chen G, Mao X, Liu C. Effects of low carbohydrate diets in individuals with type 2 diabetes: systematic review and meta-analysis. Int J Clin Exp Med. 2016;9(6):11166–11174. http://www.ijcem.com/files/ijcem0023504.pdf .

In this systematic review, low-carb diets were more effective at promoting weight loss than conventional diabetes diets in individuals with type 2 diabetes. Low-carb diets also significantly decreased hemoglobin A1c and triglycerides and increased HDL cholesterol compared to control diets. Meng Y, Bai H, Wang S, Li Z, Wang Q, Chen L. Efficacy of low carbohydrate diet for type 2 diabetes mellitus management: a systematic review and meta-analysis of randomized controlled trials. Diabetes Res Clin Pract. 2017;131:124–131. https://www.diabetesresearchclinicalpractice.com/article/S0168-8227(17)30402-3/fulltext .

In this systematic review and meta-analysis of nine studies including a total of 734 type 2 diabetic patients, low-carb diets significantly reduced hemoglobin A1c and triglycerides and increased HDL cholesterol. Subgroup analysis indicated that low-carb diets also are an effective tool for weight loss. Huntriss R, Campbell M, Bedwell C. The interpretation and effect of a low-carbohydrate diet in the management of type 2 diabetes: a systematic review and meta-analysis of randomised controlled trials. Eur J Clin Nutr. 2018;72:311–325. https://www.nature.com/articles/s41430-017-0019-4 .

In this systematic review, low-carb diets induced significant reductions in hemoglobin A1c, triglycerides, and systolic blood pressure and increased HDL cholesterol in type 2 diabetic patients. Importantly, “low-carb” diets were defined as those containing less than 130 grams of carbs per day; this is still a fairly high carbohydrate intake, so the studies may have underestimated the true impact of low-carb diets in the management of type 2 diabetes.

The Optimal Human Diet

Perry GH, Dominy NJ, Claw KG, Lee AS, Fiegler H, Redon R, Werner J, Villanea FA, Mountain JL, Misra R, et al. Diet and the evolution of human amylase gene copy number variation. Nat Genet. 2007;39(10):1256–1260. https://www.ncbi.nlm.nih.gov/pubmed/17828263?dopt=AbstractPlus .

Populations of agriculturalists and hunter–gatherers with a historically high starch intake produce more salivary amylase, an enzyme that breaks down dietary starch, than populations with traditionally low starch intakes. Hehemann J-H, Correc G, Barbeyron T, Helbert W, Czjzek M, Michel G. Transfer of carbohydrate-active enzymes from marine bacteria to Japanese gut microbiota. Nature. 2010;464:908–912. https://www.nature.com/articles/nature08937 .

Studies of Japanese people have found that they have a unique gut bacterial composition that helps them break down seaweed, which can be difficult for many humans to digest. Siri-Tarino PW, Sun Q, Hu FB, Krauss RM. Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease. Am J Clin Nutr. 2010;91(3):535–546. https://www.ncbi.nlm.nih.gov/pubmed/20071648?dopt=AbstractPlus .

Higher intakes of saturated fat are not associated with an increased risk of coronary heart disease (CHD) or cardiovascular disease (CVD). Scrinis G. On the ideology of nutritionism. Gastronomica: J Crit Food Stud. 2008;8(1):39–48. http://gcfs.ucpress.edu/content/8/1/39 .

Nutritionism, the reductive approach of understanding food only in the context of nutrients, food components, and their effects on biomarkers rather than on the source and quality of the food, is one of the main reasons why nutrition research has resulted in ineffective, and even harmful, public health recommendations and dietary guidelines. We must focus on food quality, not just food and nutrient quantities, if we truly want to understand what constitutes the optimal human diet. De Heinzelin J, Clark JD, White T, Hart W, Renne P, WoldeGabriel G, Beyene Y, Vrba E. Environment and behavior of 2.5-million-year-old Bouri hominids. Science. 1999;284(5414):625–629. https://www.ncbi.nlm.nih.gov/pubmed/10213682/ .

Archaeological studies indicate that our hominid ancestors have been eating meat for the past 2.5 million years. In fact, the advent of meat eating may have been responsible for the divergence of our more recent hominid ancestors, including members of the genus Homo, from Australopithecus, a far more primitive primate. Fahy GE, Richards M, Riedel J, Hublin J-J, Boesch C. Stable isotope evidence of meat eating and hunting specialization in adult male chimpanzees. PNAS. 2013;110(15):5829–5833. http://www.pnas.org/content/110/15/5829 .

This research indicates that meat eating and hunting are not unique to members of the genus Homo; in fact, they are common characteristics of male chimpanzees. This finding indicates that meat acquisition has been persistent throughout hominin evolution. Ireland C. Eating meat led to smaller stomachs, bigger brains. The Harvard Gazette. 2008 Apr 3. https://news.harvard.edu/gazette/story/2008/04/eating-meat-led-to-smaller-stomachs-bigger-brains/ .

Researchers believe that the consumption of meat and fish was the pivotal factor that led to larger brains and smaller guts in our hominid ancestors. Larger brains propelled our ancestors forward, creating highly intelligent, capable modern humans. Cordain L, Brand Miller J, Boyd Eaton S, Mann N, Holt SHA, Speth JD. Plant-animal subsistence ratios and macronutrient energy estimations in worldwide hunter–gatherer diets. Am J Clin Nutr. 2000;71(3):682–692. https://academic.oup.com/ajcn/article/71/3/682/4729121 .

In this comprehensive study of 229 hunter–gatherer groups, animal food was found to be the dominant source of calories (68 percent) compared to plant food (32 percent). Only 14 percent of the groups obtained more than 50 percent of their calories from plant food. Cordain L, Eaton SB, Brand Miller J, Mann N, Hill K. The paradoxical nature of hunter–gatherer diets: meat-based, yet non-atherogenic. Eur J Clin Nutr. 2002;56:S42–S52. https://www.nature.com/articles/1601353 .

Thirteen field studies of the last remaining hunter–gatherer societies found that animal foods comprised 65 percent of their total calories on average, and plant foods comprised 35 percent. This finding highlights the significance of animal foods in the natural human diet. Gurven M, Kaplan H. Longevity among hunter–gatherers: a cross-cultural examination. Popul Dev Rev. 2007;33(2):321–365. https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1728-4457.2007.00171.x .

The average lifespan is and was lower in hunter–gatherers due to high rates of infant mortality and a lack of emergency medical care; when hunter–gatherers survive childhood, their lifespans are roughly equivalent to our own. This finding contradicts the caricature of hunter–gatherer lives as “nasty, brutish, and short.” Kaplan H, Thompson RC, Trumble BC, Wann LS, Allam AH, Beheim B, Frohlich B, Sutherland ML, Sutherland JD, Stieglitz J, et al. Coronary atherosclerosis in indigenous South American Tsimane: a cross-sectional cohort study. Lancet. 2017;389(10080):1730–1739. https://www.ncbi.nlm.nih.gov/pubmed/28320601 .

The Tsimane, hunter–gatherers native to Bolivia, have an 80 percent lower prevalence of atherosclerosis compared to the United States. Nine in 10 Tsimane adults ages 40 to 94 have completely clean arteries and no risk of cardiovascular disease. Maillot M, Darmon N, Darmon M, Lafay L, Drewnowski A. Nutrient-dense food groups have high energy costs: an econometric approach to nutrient profiling. J Nutr. 2007;137(7):1815–1820. https://www.ncbi.nlm.nih.gov/pubmed/17585036 .

According to this study, the most nutrient-dense foods are organ meats, shellfish, fatty fish, lean fish, vegetables, eggs, poultry, legumes, red meat, milk, fruit, and nuts. Eight of the 12 most nutrient-dense foods are animal foods. Weaver CM, Proulx WR, Heaney R. Choices for achieving adequate dietary calcium with a vegetarian diet. Am J Clin Nutr. 1999;70(3):543s–548s. https://academic.oup.com/ajcn/article/70/3/543s/4714998 .

While plant foods included in vegetarian and vegan diets contain calcium, the bioavailability of calcium is poor due to the presence of phytates and oxalates in these foods.

Paleo Randomized Controlled Trials (RCTs)

Metabolism and Inflammation

Martin CA, Akers J. Paleo diet versus modified Paleo diet: A randomized control trial of weight loss and biochemical benefit. J Acad Nutr Diet. 2013;113(9 Suppl):A35. https://jandonline.org/article/S2212-2672(13)00793-4/fulltext .

Consuming a “modified Paleo diet” with three unrestricted meals and two unrestricted snacks over the course of a five-week study period resulted in weight loss, fat loss, lowered blood pressure, increased insulin sensitivity, and improved lipid profiles in the participants in this study. These results demonstrate that a modified Paleo diet can have beneficial physiological effects equal to those of a strict Paleo diet. Genoni A, Lo J, Lyons-Wall P, Devine A. Compliance, palatability and feasibility of Paleolithic and Australian Guide to Healthy Eating diets in healthy women: A 4-week dietary intervention. Nutrients. 2016;8(8):481. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4997394/ .

Healthy women were randomized to follow either a Paleo diet or diet guidelines outlined by the Australian Guide to Healthy Eating (AGHE), which encourages the consumption of grains, legumes, and dairy along with fruits, vegetables, meat, and fish. The results showed that compliance to the Paleo diet and AGHE diet were equal, suggesting that the Paleo diet is a feasible dietary intervention for generally healthy individuals. Genoni A, Lyons-Wall P, Lo J, Devine A. Cardiovascular, metabolic effects and dietary composition of ad-libitum Paleolithic vs. Australian Guide to Healthy Eating diets: a 4-week randomised trial. Nutrients. 2016;8(5):E314. https://www.ncbi.nlm.nih.gov/pubmed/27223304

Thirty-nine healthy women were randomized to either a Paleo diet or the AGHE diet for four weeks. Paleo dieters spontaneously ate less food, resulting in weight loss. Paleo dieters had greater weight loss and lower intakes of carbs, sodium, calcium, and iodine. Paleo dieters also had higher intakes of fat and beta-carotene. No differences were found for cardiovascular or metabolic markers. The weight loss experienced by the Paleo dieters could not explained by calorie deficit alone.

Heart Disease

Jonsson T, Granfeldt Y, Erlanson-Albertsson C, Ahrén B, Lindeberg S. A Paleolithic diet is more satiating per calorie than a Mediterranean-like diet in individuals with ischemic heart disease. Nutr Metab (Lond). 2010;7:85. https://www.ncbi.nlm.nih.gov/pubmed/21118562 .

Twenty-nine male patients with ischemic heart disease (IHD) and either impaired glucose tolerance or type 2 diabetes were randomized to either a Paleo diet or Mediterranean diet for 12 weeks. Paleo dieters reported higher degrees of satiation than Mediterranean dieters. They also experienced greater decreases in leptin, weight, and waist circumference than those on the Mediterranean diet. Lindeberg S, Jonsson T, Granfeldt Y, Borgstrand E, Soffman J, Sjöström K, Ahrén B. A Palaeolithic diet improves glucose tolerance more than a Mediterranean-like diet in individuals with ischaemic heart disease. Diabetologia. 2007;50(9):1795–1807. https://www.ncbi.nlm.nih.gov/pubmed/17583796 .

Twenty-nine male patients with ischemic heart disease (the same subjects from the study mentioned above) consumed either a Paleo diet or Mediterranean diet for 12 weeks. The patients on the Paleo diet experienced a far greater improvement in glucose tolerance than patients on the Mediterranean diet. This improvement was independent of weight loss. Manheimer EW, van Zuuren EJ, Fedorowicz Z, Pijl H. Paleolithic nutrition for metabolic syndrome: systematic review and meta-analysis. Am J Clin Nutr. 2015;102(4):922–932. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4588744/

In this meta-analysis of randomized controlled trials, it was found that Paleo diets resulted in pooled improvements in waist circumference, triglycerides, HDL cholesterol, blood pressure, and fasting blood sugar (results did not reach statistical significance for HDL and blood sugar). One limitation is that these studies were short term. Pastore RL, Brooks JT, Carbone JW. Paleolithic nutrition improves plasma lipid concentrations of hypercholesterolemic adults to a greater extent than traditional heart-healthy dietary recommendations. Nutr Res. 2015;35(6):474–479. https://www.ncbi.nlm.nih.gov/pubmed/26003334

Twenty adults with high cholesterol followed a conventional “heart-healthy” diet for four months, followed by a Paleo diet for four months. The Paleo diet lowered total cholesterol, LDL cholesterol, and triglycerides and increased HDL cholesterol relative to baseline and the conventional “heart-healthy” diet.

Obesity, Metabolic Syndrome, Type 2 Diabetes

Jönsson T, Granfeldt Y, Ahrén B, Branell UC, Pålsson G, Hansson A, Söderström M, Lindeberg S. Beneficial effects of a Paleolithic diet on cardiovascular risk factors in type 2 diabetes: a randomized cross-over pilot study. Cardiovasc Diabetol. 2009;8:35. https://www.ncbi.nlm.nih.gov/pubmed/19604407 .

Thirteen patients with type 2 diabetes were randomized to either a Paleo diet or a conventional diabetes diet for three months. Over the three-month study period, the Paleo diet resulted in improved glycemic control, hemoglobin A1c, triglycerides, diastolic blood pressure, weight, BMI, and waist circumference compared to the conventional diabetes diet. Otten J, Stomby A, Waling M, Isaksson A, Tellström A, Lundin-Olsson L, Brage S, Ryberg M, Svensson M, Olsson T. Benefits of a Paleolithic diet with and without supervised exercise on fat mass, insulin sensitivity, and glycemic control: a randomized controlled trial in individuals with type 2 diabetes. Diabetes Metab Res Rev. 2017;33(1):e2828. https://www.ncbi.nlm.nih.gov/pubmed/27235022 .

Thirty-two patients with type 2 diabetes followed a Paleo diet for 12 weeks. The participants experienced improved insulin sensitivity and glycemic control and decreased leptin. Otten J, Stomby A, Waling M, Isaksson A, Söderström I, Ryberg M, Svensson M, Hauksson J, Olsson T. A heterogeneous response of liver and skeletal muscle fat to the combination of a Paleolithic diet and exercise in obese individuals with type 2 diabetes: a randomised controlled trial. Diabetologia. 2018;61(7):1548–1559. https://www.ncbi.nlm.nih.gov/pubmed/29696296 .

In 32 obese patients with type 2 diabetes, an ad libitum Paleo diet reduced liver fat and intramyocellular lipid content, which are lipid droplets stored in muscle cells. These results indicate that the Paleo diet has beneficial effects on liver and skeletal muscle fat storage in diabetic individuals. Fontes-Villalba M, Lindeberg S, Granfeldt Y, Knop FK, Memon AA, Carrera-Bastos P, Picazo Ó, Chanrai M, Sunquist J, Sundquist K, et al. Paleolithic diet decreases fasting plasma leptin concentrations more than a diabetes diet in patients with type 2 diabetes: a randomised cross-over trial. Cardiovasc Diabetol. 2016;15:80. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4877952/ .

In 13 patients with type 2 diabetes, a Paleo diet significantly lowered fasting plasma leptin levels compared to a conventional diabetes diet. Genetic and in vitro studies suggest that the human leptin system is ill adapted to a diet based on cereal grains, and a grain-based diet may promote leptin resistance. This explains why the grain-free Paleo diet may be beneficial for restoring leptin sensitivity. Frassetto LA, Shi L, Schloetter M, Sebastian A, Remer T. Established dietary estimates of net acid production do not predict measured net acid excretion in patients with Type 2 diabetes on Paleolithic-Hunter-Gatherer-type diets. Eur J Clin Nutr. 2013;67(9):899–903. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4209958/ .

The Paleo diet produces a lower net acid excretion than the conventional diabetes diet promoted by the American Diabetes Association. The high fruit and vegetable content of the Paleo diet may help reduce net acid load. Boers I, Muskiet FAJ, Berkelaar E, Schut E, Penders R, Hoenderdos K, Wichers HJ, Jong MC. Favourable effects of consuming a Palaeolithic-type diet on characteristics of the metabolic syndrome: a randomized controlled pilot-study. Lipids Health Dis. 2014;13:160. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4210559/

Thirty-four subjects with metabolic syndrome consumed a Paleo diet for two weeks. They experienced significant decreases in systolic and diastolic blood pressure, total cholesterol, and triglycerides, along with increased HDL cholesterol. Body weight also decreased in the Paleo diet group. Genoni A, Lyons-Wall P, Lo J, Devine A. Cardiovascular, metabolic effects and dietary composition of ad-libitum Paleolithic vs. Australian Guide to Healthy Eating diets: a 4-week randomised trial. Nutrients. 2016;8(5):E314. https://www.ncbi.nlm.nih.gov/pubmed/27223304

Subjects assigned to an ad libitum Paleo diet for four weeks spontaneously ate less food, resulting in weight loss. They had higher intakes of fat and beta-carotene and lower intakes of carbs, sodium, calcium, and iodine. The weight loss experienced by the subjects could not explained by calorie deficit alone. Jönsson T, Granfeldt Y, Lindeberg S, Hallberg AC. Subjective satiety and other experiences of a Paleolithic diet compared to a diabetes diet in patients with type 2 diabetes. Nutr J. 2013;12:105. https://www.ncbi.nlm.nih.gov/pubmed/23890471

In this six-month cross-over study that included 13 diabetic patients, the Paleo diet proved to be more satiating, despite lower fiber content, than the conventional diabetes diet. The Paleo diet was lower in carbohydrates and higher in protein than the conventional diabetes diet. Mellberg C, Sandberg S, Ryberg M, Eriksson M, Brage S, Larsson C, Olsson T, Lindahl B. Long-term effects of a Palaeolithic-type diet in obese postmenopausal women: a two-year randomized trial. Eur J Clin Nutr. 2014;68(3):350–357. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4216932/

In this study, 70 obese postmenopausal women were randomized to follow either Paleo or Nordic Nutrition Recommendations (NNR) for two years. Paleo dieters lost more fat and experienced decreased waist circumference and triglyceride levels at six months compared to those following the NNR. Triglycerides were also lower at 24 months in the Paleo group compared to the NNR group. However, the difference between the two groups was not significant after two years. Importantly, Paleo dieters didn’t reach the target protein intake of 30 percent of total calories, according to their urine nitrogen tests; this could have impacted their satiety and eating habits, and ultimately, their physiological outcomes. Masharani U, Sherchan P, Schloetter M, Stratford S, Xiao A, Sebastian A, Nolte Kennedy M, Frassetto L. Metabolic and physiologic effects from consuming a hunter-gatherer (Paleolithic)-type diet in type 2 diabetes. Eur J Clin Nutr. 2015;69(8):944–948. https://www.ncbi.nlm.nih.gov/pubmed/25828624

In this study of type 2 diabetes patients, 14 were assigned to a Paleo diet and 10 to a conventional diabetes diet. Patients on the Paleo diet experienced greater benefits in terms of glucose control and circulating blood lipid levels. Most insulin-resistant Paleo dieters showed improvements in insulin sensitivity; however, this did not occur in the patients on the conventional diabetes diet.

Autoimmune Disease

Irish AK, Erickson CM, Wahls TL, Snetselaar LG, Darling WG. Randomized control trial evaluation of a modified Paleolithic dietary intervention in the treatment of relapsing-remitting multiple sclerosis: a pilot study. Degener Neurol Neuromuscul Dis. 2017;7:1–18. https://www.ncbi.nlm.nih.gov/pubmed/30050374

A Paleo diet improves fatigue, increases mental and physical abilities, increases exercise capacity, and improves hand and leg function in patients with MS. By increasing vitamin K levels, it may also reduce inflammation.

Paleo Diet Studies (Non-RCT)

Metabolism and Insulin Sensitivity

Frassetto LA, Schloetter LM, Mietus-Snyder M, Morris RC Jr, Sebastian A. Metabolic and physiologic improvements from consuming a paleolithic, hunter-gatherer type diet. Eur J Clin Nutr. 2009;63(8):947–955. https://www.ncbi.nlm.nih.gov/pubmed/19209185 .

Even short-term consumption of a Paleo diet (10 days) significantly improves blood pressure, increases glucose tolerance and insulin sensitivity, decreases insulin secretion, and improves blood lipid profiles in adults. Jönsson T, Ahrén B, Pacini G, Sundler F, Wierup N, Steen S, Sjöberg T, Ugander M, Frostegård J, Göransson L, et al. A Paleolithic diet confers higher insulin sensitivity, lower C-reactive protein and lower blood pressure than a cereal-based diet in domestic pigs. Nutr Metab (Lond). 2006;3:39. https://www.ncbi.nlm.nih.gov/pubmed/17081292 .

In this animal study, pigs that consumed a Paleo diet (consisting of vegetables, fruit, meat, and tubers) for 17 months experienced higher insulin sensitivity, lower C-reactive protein, and lower blood pressure than pigs fed a grain-based diet. The pig model is one of the best non-primate models for human health disorders; thus, the results of this study may be extrapolated to humans.

Cardiovascular Disease

Osterdahl M, Kocturk T, Koochek A, Wandell PE. Effects of a short-term intervention with a paleolithic diet in healthy volunteers. Eur J Clin Nutr. 2008;62(5):682–685. https://www.ncbi.nlm.nih.gov/pubmed/17522610 .

Twenty subjects consumed a Paleo diet for three weeks. Over the course of the study period, the mean body weight, BMI, waist circumference, systolic blood pressure, and levels of plasminogen activator inhibitor, a biomarker predictive of cardiovascular disease, all decreased significantly. These results indicate that a Paleo diet has favorable effects on cardiovascular disease risk factors.

Inflammation and Oxidative Stress

Whalen KA, McCullough ML, Flanders WD, Hartman TJ, Judd S, Bostick RM. Paleolithic and Mediterranean diet pattern scores are inversely associated with biomarkers of inflammation and oxidative balance in adults. J Nutr. 2016;146(6):1217–1226. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4877627/ .

The consumption of diets that are more Paleolithic or more Mediterranean style, as assessed by food frequency questionnaire, is associated with lower levels of systemic inflammation and oxidative stress. Factors in the two diets that may contribute to reductions in inflammation and oxidative stress include high consumptions of fruit, vegetables, fish, and nuts, a lower glycemic load, and a more favorable omega-6/omega-3 fatty acid ratio.

Type 2 Diabetes

O’Dea K. Marked improvement in carbohydrate and lipid metabolism in diabetic Australian aborigines after temporary reversion to traditional lifestyle. Diabetes. 1984;33(6):596–603. https://www.ncbi.nlm.nih.gov/pubmed/6373464 .

Diabetic Australian Aborigines who consumed a traditional diet experienced significant declines in fasting blood glucose, insulin, and triglycerides, and an improvement in postprandial glucose clearance. Their diet was high in wild game and plant foods.

Autoimmune Disease

Konijeti GG, Kim N, Lewis JD, Groven S, Chandrasekaran A, Grandhe S, Diamant C, Singh E, Oliveira G, Wang X, et al. Efficacy of the autoimmune protocol diet for inflammatory bowel disease. Inflamm Bowel Dis. 2017;23(11):2054–2060. https://www.ncbi.nlm.nih.gov/pubmed/28858071.

A Paleo diet decreases fecal calprotectin, a marker of intestinal inflammation, and reduces symptoms in patients with inflammatory bowel disease.

Epilepsy

Clemens Z, Kelemen A, Fogarasi A, Tóth C. Childhood absence epilepsy successfully treated with the paleolithic ketogenic diet. Neurol Ther. 2013;2(1–2):71–76. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4389034/ .

In a seven-year-old child, absence epilepsy was successfully treated with a ketogenic Paleo diet. Seizure freedom was achieved within six weeks of following the diet. Developmental and behavioral improvements also occurred.

Anthropological Studies of Hunter–Gatherers

Acne

Cordain L, Lindeberg S, Hurtado M, Hill K, Eaton SB, Brand-Miller J. Acne vulgaris: a disease of Western civilization. Arch Dermatol. 2002;138(12):1584–1590. https://www.ncbi.nlm.nih.gov/pubmed/12472346 .

This epidemiological study of 1,200 Kitavans, the indigenous people of the Trobriand Islands, revealed a complete absence of acne. A parallel study of 112 Ache people, a group of hunter–gatherers indigenous to Paraguay, similarly found not a single case of active acne. The authors suggest that acne is a disease of Western civilization induced by our insulinogenic industrialized diet.

Cancer

Dewailly E, Mulvad G, Sloth Pedersen H, Hansen JC, Behrendt N, Hart Hansen JP. Inuit are protected against prostate cancer. Cancer Epidemiol Biomarkers Prev. 2003;12(9):926–927. https://www.ncbi.nlm.nih.gov/pubmed/14504206 .

The traditional diet of the Inuit, which is extraordinarily high in animal foods and fat, is associated with a reduced risk of cancer. The large amount of omega-3 fatty acids in the traditional Inuit diet may be responsible, in part, for the anticancer effect.

Cardiovascular Disease

Kaplan H, Thompson RC, Trumble BC, Wann LS, Allam AH, Beheim B, Frohlich B, Sutherland ML, Sutherland JD, Stieglitz J, et al. Coronary atherosclerosis in indigenous South American Tsimane: a cross-sectional cohort study. Lancet. 2017;389(10080):1730–1739. https://www.ncbi.nlm.nih.gov/pubmed/28320601 .

The Tsimane, a hunter–gatherer/horticulturist population living in the Bolivian Amazon, have the lowest reported levels of coronary artery disease of any population recorded to date. Their exemplary cardiovascular health may be attributed to their pre-industrial diet consisting of animal protein and fat acquired from hunting, freshwater fish, rice, plantain, manioc, corn, wild nuts, and fruits and their extremely active lifestyles. Sinnett PF, Whyte HM. Epidemiological studies in a total highland population, Tukisenta, New Guinea: cardiovascular disease and relevant clinical, electrocardiographic, radiological, and biochemical findings. J Chron Dis. 1973;26(5):265–290. https://www.sciencedirect.com/science/article/pii/0021968173900313 .

The indigenous Tukisenta people of New Guinea have a high glucose tolerance, are free of diabetes and gout, and have a very low prevalence of cardiovascular disease. Notably, carbohydrate provides more than 90 percent of their total calorie intake. Lindeberg S, Nilsson-Ehle P, Terént A, Vessby B, Scherstén B. Cardiovascular risk factors in a Melanesian population apparently free from stroke and ischaemic heart disease: the Kitava study. J Intern Med. 1994;236(3):331–340. https://www.ncbi.nlm.nih.gov/pubmed/8077891 .

The Kitavans, horticulturalists indigenous to the Trobriand Islands, eat a diet uninfluenced by the Western world. Compared to industrialized people living in Sweden, they are leaner and have significantly lower blood pressure, total cholesterol, LDL cholesterol, and apolipoprotein B. Together, these factors are likely responsible for their very low rates of heart disease and ischemic stroke. Cordain L, Eaton SB, Brand Miller J, Mann N, Hill K. The paradoxical nature of hunter-gatherer diets: meat-based, yet non-atherogenic. Eur J Clin Nutr. 2002;56:S42–S52. https://www.nature.com/articles/1601353 .

In this review of 13 studies of hunter–gatherer populations, animal foods provided the dominant energy source, at approximately 65 percent of total calories, with plant foods providing the remaining 35 percent of total calories. The high reliance on animal foods in these societies is accompanied by either an extremely low prevalence or a complete absence of cardiovascular disease; these findings suggest that hunter–gatherer diets are non-atherogenic. Pavan L, Casiglia E, Braga LM, Winnicki M, Puato M, Pauletto P, Pessina AC. Effects of a traditional lifestyle on the cardiovascular risk profile: the Amondava population of the Brazilian Amazon. Comparison with matched African, Italian and Polish populations. J Hypertens. 1999;17(6):749–756. https://www.ncbi.nlm.nih.gov/pubmed/10459871 .

In the Amondava people of the Brazilian Amazon, a traditional diet and lifestyle may protect against hypertension, diabetes, and dyslipidemia.

Dental Health

Crittenden AN, Sorrentino J, Moonie SA, Peterson M, Mabulla A, Ungar PS. Oral health in transition: the Hadza foragers of Tanzania. PLoS One. 2017;12(3):e0172197. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0172197 .

Hadza women who have transitioned from the traditional hunter–gatherer diet to an agricultural diet have a higher prevalence of dental caries and periodontal disease than those who live in the bush and consume a wild-food diet.

Insulin Resistance and Type 2 Diabetes

Kuroshima A, Itoh S, Azuma T, Agishi Y. Glucose tolerance test in the Ainu. Int J Biometerol. 1972;16(2):193–197. https://link.springer.com/article/10.1007/BF01810290 .

The Ainu, a population indigenous to Japan that subsists primarily on hunting and fishing, have significantly lower fasting levels of free fatty acids compared to industrialized Japanese people. High levels of free fatty acids are associated with impaired glucose metabolism, obesity, and type 2 diabetes. This finding suggests that the diet and lifestyle of the Ainu reduce their risk of these health conditions. Spielman RS, Fajans SS, Neel JV, Pek S, Floyd JC, Oliver WJ. Glucose tolerance in two unacculturated Indian tribes of Brazil. Diabetologia. 1982;23(2):90–93. https://www.ncbi.nlm.nih.gov/pubmed/6751901 .

This study assessed the glucose tolerance of two unacculturated tribes in Brazil, the Yanomami and Marubo. The researchers found that the Yanomami, who live a hunter–gatherer lifestyle, had significantly better glucose tolerance than the Marubo, who are more acculturated to the Western lifestyle. Lindgärde F, Widén I, Gebb M, Ahrén B. Traditional versus agricultural lifestyle among Shuar women of the Ecuadorian Amazon: effects on leptin levels. Metabolism. 2004;53(10):1355–1358. https://www.ncbi.nlm.nih.gov/pubmed/15375794 .

This study of 59 Shuar women, who live a hunter–gatherer lifestyle in the Ecuadorian Amazon, found that they had the lowest leptin concentrations ever reported for a concentration of healthy females. Elevated leptin is associated with disturbed metabolic function and obesity. The Shuar women also had lower fat mass and BMI than the Yuwientsa, a neighboring community that depends on agriculture, rather than hunting and foraging, for food. Lindeberg S, Eliasson M, Lindahl B, Ahrén B. Low serum insulin in traditional Pacific Islanders—the Kitava Study. Metabolism. 1999;48(10):1216–1219. https://www.ncbi.nlm.nih.gov/pubmed/10535381 .

The Kitavans, indigenous to the Trobriand Islands, have low serum insulin, blood pressure, and BMI. The intake of processed Western foods is negligible in this population, suggesting that the Western diet is a primary cause of insulin resistance. Martin FI, Wyatt GB, Griew AR, Haurahelia M, Higginbotham L. Diabetes mellitus in urban and rural communities in Papua New Guinea. Studies of prevalence and plasma insulin. Diabetologia. 1980;18(5):369–374. https://www.ncbi.nlm.nih.gov/pubmed/7000592 .

In Papua New Guinea, nearly 16 percent of urbanized people have diabetes mellitus and 22 percent are glucose intolerant, compared to 1 percent and 5.5 percent, respectively, of rural people. The differences in diet between these two groups—urbanized New Guineans eat a Westernized diet, whereas rural villagers practice horticulture, hunting, and gathering—may be responsible for these physiological differences.

Gut Microbiome

Schnorr SL, Candela M, Rampelli S, Centanni M, Consolandi C, Basaglia G, Turroni S, Biagi E, Peano C, Severgnini M, et al. Gut microbiome of the Hadza hunter-gatherers. Nat Commun. 2014;5:article number 3654. https://www.