Welcome, Joe Rogan fans! On this page, you’ll find a summary of the topics discussed on the September 27th, 2018, episode where I debated Dr. Joel Kahn on the health impacts of eating meat. You can watch the replay here. You’ll also find links to articles, resources, and scientific studies relevant to the debate. Enjoy!

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What Is the Optimal Human Diet?

This is an impossible question to answer because there is no single optimal diet for every individual. That said, there are core principles of nutrition that apply to all human beings, and we can discover them in two ways:

By looking through the lens of evolutionary biology, archeology, medical anthropology, and comparative anatomy and physiology; and By looking through the lens of biochemistry—what nutrients contribute to human health (and where are they found in foods), how do various functional components of food influence our body at the cellular and molecular level, and how do certain compounds in foods damage our health.

Looking through either of these lenses brings us to the same conclusion: the natural human diet contains both animal and plant foods.

For a deeper dive on this topic:

What Is Nutrient Density, Why Is It Important, and What Diet Is the Most Nutrient-Dense?

The term nutrient density refers to the concentration of micronutrients and amino acids, the building blocks of proteins, in a given food. Despite a high intake of calories, Americans have high rates of deficiency of vitamins A, B6, B12, C, D, E, and folate, as well as the mineral iron. Maximizing nutrient density should be the primary goal of our diet because deficiencies of any of these essential nutrients can contribute to the development of chronic disease and even shorten our lifespan. A diet that contains both animal and plant foods is the best way to maximize nutrient density because animal foods are higher in some nutrients (B12, iron, zinc, EPA and DHA, etc.) and plant foods are higher in others (flavonoids, carotenoids, diallyl sulfides, lignans, fiber, etc.).

For a deeper dive on this topic:

Do Vegetarians and Vegans Suffer from Higher Rates of Nutrient Deficiencies than Omnivores?

Humans require about 20 amino acids and about 40 micronutrients (vitamins, minerals, and trace minerals) for optimal function; suboptimal intake of any of these nutrients will increase the risk of chronic disease and reduce the quality of life. Vegetarian, and especially vegan, diets are lower in several essential nutrients, including vitamins A, B12, and D, as well as calcium, iron, zinc, iodine, choline, selenium, creatine, taurine, methionine, glycine, and EPA and DHA. This is especially true if bioavailability—the portion of a nutrient that is absorbed in the digestive tract—is considered. Studies suggest that vegetarians and vegans are significantly more likely to be deficient in these nutrients. For example, a recent study assessing B12 status found that 92 percent of vegans and 77 percent of vegetarians were deficient, compared to just 11 percent of omnivores.

For a deeper dive on this topic:

Do Vegetarians and Vegans Live Longer than Omnivores?

Early studies suggested that vegetarians live longer than omnivores. These studies have been heavily criticized because they compared Seventh Day Adventists, a religious group that embraces healthy lifestyle choices as part of their belief system, with the general population. Later studies that compared vegetarians with healthy omnivores found that both groups had longer lifespans than people following a Standard American Diet and lifestyle, but there was no difference in longevity between omnivores and vegetarians.

For a deeper dive on this topic:

Are Vegetarian and Vegan Diets Safe for Pregnant Women and Children?

Both the USDA and the Academy of Nutrition and Dietetics (AND) have said that vegetarian and vegan diets are safe during pregnancy, but critical analyses by several researchers have questioned whether these recommendations are based on sufficient evidence. One review remarked that “Realistic vegetarian diets put children at risk for deficiencies that may have both short-term and permanent negative health consequences.” The more restricted the diet and the younger the child, the greater the risk of deficiencies.

For a deeper dive on this topic:

Doesn’t Eating Saturated Fat and Cholesterol Increase the Risk of Heart Disease?

Most of us grew up being told that foods like red meat, eggs, and bacon raise our cholesterol levels. This idea is so deeply ingrained in our cultural psyche that few people even question it. But is it really true? In 2015, the U.S. government quietly revised dietary guidelines and dropped the strict limit on cholesterol that had been in place since the 1960s because newer evidence didn’t support an association between eating cholesterol in the diet and heart disease. Strict limits on saturated fat will also likely be dropped in the future. A meta-analysis of randomized, controlled trials of low-carb diets (which tend to be high in saturated fat) have shown that they have beneficial impacts on several cardiovascular disease risk markers, including body weight, triglycerides, fasting glucose, blood pressure, body mass index, abdominal circumference, plasma insulin, HDL cholesterol, and C-reactive protein. Moreover, an exhaustive review of studies involving more than 600,000 participants concluded that “Current evidence does not clearly support cardiovascular guidelines that encourage high consumption of polyunsaturated fatty acids and low consumption of total saturated fats.”

For a deeper dive on these topics:

What about Red Meat? Doesn’t It Increase the Risk of Heart Disease and Cancer?

Red meat has been associated with an increase in heart disease and cancer in several studies. But correlation is not causation, and there are numerous reasons to be skeptical of the research on this topic. Countless studies have found that people who eat more red meat have a higher BMI; are more likely to be overweight/obese, smoke cigarettes, and be physically inactive; and are less likely to eat fresh fruits and vegetables and have higher than a high-school education. All of these variables are associated with a higher risk of heart disease and cancer, so it’s not possible to isolate red meat as the cause. Many recent studies have cast doubt on the theory that consuming red meat contributes to disease. Red meat (especially grass-fed) is rich in several bioavailable nutrients—like B12, zinc, iron, CLA, and EPA and DHA—that Americans and people around the world are commonly deficient in.

For a deeper dive on these topics:

Aren’t Low-Fat Diets More Effective than Low-Carb for Weight Loss?

The U.S. dietary guidelines, and organizations like the American Heart Association and American Diabetic Association, continue to recommend low-fat diets for weight loss and disease prevention. There have been 10 meta-analyses of low-carb diets. All 10 showed that low-carb diets were either as effective or more effective than low-fat diets. That said, low-carb diets aren’t appropriate for everyone, and some may do better on a moderate-carb or even high-carb approach.

For a deeper dive on these topics:

Low-Carb Diets May Be More Effective for Weight Loss, but Are They Safe for People with Diabetes or Cardiovascular Disease? And What about That Study That Showed That Low-Carb Diets Shorten Lifespan?

This is also a common misconception. A meta-analysis of RCTs has shown that low-carb diets are more effective than high-carb diets for patients with type 2 diabetes, and another meta-analysis showed that low-carb diets lead to improvement of several cardiovascular risk markers. RCTs have also shown that low-carb and ketogenic diets are more effective than hypocaloric or conventional low-fat diets for improving glycemic control in patients with type 2 diabetes: see here, here, and here. As for the study claiming that low-carb diets shorten lifespan, it was riddled with methodological problems and has been widely criticized.

However, as I said above, low-carb and ketogenic diets aren’t appropriate in all cases, and some individuals may experience an increase in LDL particle number and other unfavorable changes in lipid markers on a high-fat, low-carb diet. This is one of the many reasons why I’ve argued that there is no “one-size-fits-all” approach when it comes to diet.

For a deeper dive on these topics:

Why Do the U.S. Government and Institutions like the American Dietetics Association, American Heart Association, and American Diabetes Association Continue to Recommend Low-Fat and Vegetarian Diets?

Dietary guidelines and public policy on nutrition are primarily informed by observational nutrition studies. These studies suffer from a variety of problems, including inaccurate methods of data collection (questionnaires that depend on faulty human memory), healthy user bias (people who engage in one behavior perceived as unhealthy also engage in other behaviors perceived as unhealthy), relative risks that are indistinguishable from chance, data manipulation, results that fail to be replicated in randomized, controlled trials, conflicts of interest (both financial and non-financial), and a misguided focus on quantity (of macronutrients, calories, etc.) rather than quality (types of foods consumed).

What’s more, nutrition policy in the United States has been heavily influenced by both politics and religion. The Seventh Day Adventist church—which originally advocated a vegetarian diet on moral grounds and to “suppress carnal urges”—was instrumental in the founding of the American Dietetic Association, the creation of nutrition curriculum at medical schools, and much of the research supporting vegetarian diets.

Dr. John Ioannidis, one of the most respected epidemiologists in the world and a professor at the Stanford School of Medicine, acknowledged these issues in a recent editorial when he said, “The emerging picture of nutritional epidemiology is difficult to reconcile with good scientific principles. The field needs radical reform.”

For a deeper dive on these topics:

My Doctor Said There’s Not Enough Research to Support the Paleo Diet. Is That True?

Your doctor is likely referring to the relatively low number of observational studies and randomized controlled trials specifically examining the Paleo diet. This is due to the fact that the modern concept of a Paleo diet is only about 30 years old and has only gained significant attention in the past 10 years. However, when you consider research in anthropology, archeology, evolutionary biology, comparative anatomy and physiology, and biochemistry that has shed light on what humans should eat, there are tens of thousands of studies that support the Paleo concept. (See “What Is the Optimal Human Diet?” above for more detail on this.)

And, in the last few years, roughly 30 clinical trials and a handful of RCTs on the Paleo diet have shown benefits like improved lipid profiles, insulin sensitivity, glycemic control, and body weight and composition, as well as reduced fat accumulation in the liver. The Paleo diet also compared well against the Mediterranean and low-fat diets.

For a deeper dive on this topic:

What about the Ketogenic Diet?

It’s certainly true that there’s not as much research on ketogenic diets as there is on low-fat or non-ketogenic low-carb diets, as they have only risen in popularity over the past few years. But that doesn’t mean there isn’t any research. A 2017 review of the effects of ketogenic diets on cardiovascular risk factors found that the ketogenic diet is associated with improvements in cardiovascular risk factors—such as obesity, type 2 diabetes, and HDL cholesterol levels. A 2013 meta-analysis of RCTs found that very-low-carb ketogenic diets (VLCKD) led to greater weight loss than low-fat diets, and trials in 2004 and 2006 showed that very-low-carb diets reduced cardiovascular risk factors. Ketogenic diets have also been shown to be effective for Parkinson’s disease, Alzheimer’s disease and dementia, and epilepsy in adults and children, and they have shown promising results for traumatic brain injury.

What about the Carnivore Diet?

The carnivore, or “all-meat” diet, is the latest hot trend. I don’t doubt the anecdotal reports springing up all over the internet of people that have found remarkable relief from debilitating chronic health problems with this diet, where nothing else they had tried worked. However, we need to be very careful about making the assumption that an intervention that works well in the short term would be safe and effective in the long term. Water fasting is a perfect example. Fasting is one of the most effective short-term treatments for chronic disease that we know about, and yet it’s obviously not sustainable over the long term. My belief is that the carnivore diet essentially mimics some of the benefits of fasting, but because it provides both nutrition and calories, people are able to sustain those benefits for longer.

That does not mean that there aren’t potential consequences to the carnivore diet over the long term. Plant foods contain several beneficial compounds, including vitamin C, carotenoids, diallyl sulfides, polyphenols, dithiolethiones, lignans, isothiocyanates, and indoles, plus prebiotic fibers. The available research on the action of these compounds suggests that eliminating them completely may be harmful over the long term, so I can’t recommend the carnivore diet for anything more than short-term use without more research indicating that it’s safe.

But I’ve Heard That Animal Products Are Acidic, and Our Bodies Should Be Alkaline.

It’s true that foods do leave behind alkaline or acid ash, and in general animal foods are acid forming whereas plant foods are alkaline forming. It’s also true that what we eat will temporarily cause changes in urine pH. However, food consumption does not change blood pH, which is tightly controlled at 7.4, and urine pH does not correlate with health. What’s more, clinical trials don’t support the acid–alkaline hypothesis.

For a deeper dive on this topic:

Where Do Dairy Products Fit In?

The conventional view on dairy products suggests that nonfat and low-fat dairy is beneficial; the main issue with dairy from this perspective is that it’s very high in saturated fat. On the other hand, vegans and Paleo diet advocates believe that dairy products are unhealthy regardless of fat content. But what does the research say? In a 2013 meta-analysis of 16 studies, 11 found an inverse relationship between high-fat dairy and body fat. High-fat dairy was either inversely or not associated with markers of metabolic and cardiovascular health. Three more recent reviews in 2016 and 2017 (here, here, and here) found similar results: full-fat dairy products were inversely associated with weight gain and obesity and either inversely associated or not associated with cardiovascular disease.

The evidence on dairy products reveals a significant chink in the armor of the “diet–heart hypothesis,” the idea that eating saturated fat increases the risk of heart disease. Why? Because dairy is the only food group that contains more saturated than unsaturated fat. All other food groups—including red meat, pork, eggs, and other animal products—contain more unsaturated than saturated fat. If saturated fat is fattening and increases the risk of heart disease, then how is it possible that people who consume more full-fat dairy products have either a lower risk, or at least not an increased risk, of obesity, diabetes, and cardiovascular disease?

This doesn’t mean dairy products are safe for everyone. Those who are intolerant of lactose, the sugar in dairy, may need to limit themselves to high-fat dairy products that don’t contain much lactose, like ghee, butter, hard cheese, and cream. Those who are intolerant of dairy proteins will likely need to avoid dairy altogether, with the possible exception of ghee.

For a deeper dive on these topics:

Why Quality Is Far More Important than Quantity When It Comes to Diet

Nutrition research has assumed that a carbohydrate is a carbohydrate, a fat is a fat, and a protein is a protein, no matter what type of food they come packaged in. If one person eats 50 percent of calories from fat in the form of donuts, pizza, candy, and fast food and another person eats 50 percent of calories from fat in the form of whole foods like meat, fish, avocados, nuts, and seeds, they will be lumped together in the same “50 percent of calories from fat” group in most studies.

Most people are shocked to learn that this is how nutrition research works. It doesn’t take a trained scientist to understand why this would be problematic. And yet, although there are some signs that the tide is turning, the vast majority of epidemiological studies that have served as the basis for public health recommendations and dietary guidelines are plagued by this focus on quantity over quality.

For a deeper dive on this topic:

Aren’t Vegetarian and Vegan Diets Better for the Environment?

Some people choose vegetarian or vegan diets because they believe they are better for the environment. But while there’s no doubt that CAFO meat is harmful for the environment, the same can’t be said for animals that are raised on pasture. In fact, several scientists have made the argument that grazing animals are critical for healthy ecosystems and preventing desertification, a growing problem around the world.

For a deeper dive on these topics:

Compilation links:

Media:

Articles:

Podcasts:

Books:

Scientific papers:

Stanley 2018 – This paper conducts a life-cycle assessment, including a direct measure of carbon flux, on various livestock finishing systems and shows that properly managed livestock create an ecosystem that is a net carbon sink instead of net carbon emitter.

Teague 2017 – This paper is an overarching discussion on various types of grazing management and the potential for proper (holistic) management to regenerate ecosystem function and grazing land livelihoods. It also dives into the shortcomings of most grazing research that reduces whole ecosystem complexities into individual factors.

Teague 2016 – Properly managed grazing, if applied to 25 percent of our crop and grasslands, would mitigate the entire carbon footprint of North American agriculture.

Rowntree 2016 – “From this data, we conclude that well-managed grazing and grass-ﬁnishing systems in environmentally appropriate settings can positively contribute to reducing the carbon footprint of beef cattle, while lowering overall atmospheric CO2 concentrations.”

Peters 2016 – This study modeled human carrying capacity under 10 diet scenarios. Even though carrying capacity was generally higher for diets with less meat (likely due to modeling being based on feedlot stats and the cropland needed to grow the feed), “the carrying capacity of the vegan diet was lower than two of the healthy omnivore diet scenarios.”

Machmuller 2015 – “Farms accumulated carbon at 8.0 Mg ha−1 yr−1, increasing cation exchange and water holding capacity by 95% and 34%, respectively. Thus, within a decade of management-intensive grazing practices, soil carbon levels returned to those of native forest soils and likely decreased fertilizer and irrigation demands. Emerging land uses, such as management-intensive grazing, may offer a rare win-win strategy combining profitable food production with rapid improvement of soil quality and short-term climate mitigation through soil carbon-accumulation.”

Herrero 2011 – This paper specifically calls out the often quoted but incorrect stat that 51 percent of greenhouse gas emissions are from livestock. The actual number is closer to 15 percent, but it’s important to remember that these numbers are derived from industrial livestock production methods. Papers above from Richard Teague and Paige Stanley show an alternative approach whereby properly managed livestock can regenerate grassland ecosystems and sequester carbon.

What about the Ethical Reasons for Eating a Vegetarian Diet?

I was a vegan myself earlier in my life, and a vegetarian before that. I love animals, I care about how they are treated, and I understand why people would choose a vegetarian or vegan diet for these reasons. As I looked more deeply into this, I began to question some of my assumptions and beliefs surrounding the ethics of omnivorous and vegetarian diets. This is a complex, nuanced, and ultimately personal topic, so I recommend that anyone that is genuinely interested in exploring it further read the material below and come to their own conclusions.

For a deeper dive on these topics: