There has been a history of enthusiasm for protein in the nutrition world. A century ago, the protein recommendations were more than twice what we know them to be today. This enthusiasm peaked in the 1950s with the United Nations identifying protein deficiency as a serious, widespread, global problem. According to them, there was a worldwide protein gap that needed to be filled. This was certainly convenient for the U.S. dairy industry, who could then “dump” their postwar surplus of dried milk “in developing countries than to have to just bury it in the United States as was contemplated by the Department of Agriculture at one point.” But all of this led to the phenomena I cover in my video The Great Protein Fiasco.

It started in the 1930s with a disease of malnutrition called kwashiorkor, which was assumed to be caused by protein deficiency. The disease was famously discovered by Dr. Cicely Williams, who then spent the latter part of her life debunking the very condition she had first described. It turns out “there is no real evidence of dietary protein deficiency.” The actual “cause of kwashiorkor remains obscure,” but fecal transplant studies suggest changes in gut flora may be a causal factor. How could the field of nutrition have gotten it so spectacularly wrong?

A famous editorial about the nutrition profession started with these words: “The dispassionate objectivity of scientists is a myth. No scientist is simply involved in the single-minded pursuit of truth, he [or she] is also engaged in the passionate pursuit of research grants and professional success. Nutritionists may wish to attack malnutrition, but they also wish to earn their living in ways they find congenial.”

“This inevitably encourages researchers to ‘make a case’ for the importance of their own portion of the field and ‘their nutrient,’” which in this case was protein.

Science did eventually prevail. There was a “massive recalculation of human protein requirements in the 1970s which ‘at the stroke of a pen’ closed the ‘protein gap’ and destroyed the theory of pandemic ‘protein malnutrition.’” Infant protein requirements went from a recommended 13 percent of daily calories down to 10 percent, 7 percent, and then down to 5 percent. To this day, however, there are still those obsessing about protein. For example, those promoting Paleolithic diets try to make the case for protein from an evolutionary perspective.

Okay, so what is the perfect food for human beings that has been fine-tuned over millions of years to contain the perfect amount of protein just for us?

Human breast milk.

“If high-quality protein was the ‘nutrient among nutrients’” that helped us build our big brains over the last few million years, “one would expect that importance to be resoundingly reflected in the composition of human breast milk,” especially because infancy is the time of our most rapid growth. But this is patently not the case. “In fact, human breast milk is one of the lowest-protein milks in the mammalian world…” Indeed, it may have the lowest protein concentration of any animal in the world, at less than 1 percent protein by weight. This is one of the reasons why feeding straight cow’s milk to babies can be so dangerous. And, although the protein content in human milk has been described as extremely low, it’s exactly where it needs to be—at the natural, normal level for the human species, fine-tuned over millions of years.

Adults require no more than 0.8 or 0.9 grams of protein per healthy kilogram of body weight per day, which is about your ideal weight in pounds multiplied by four and then divided by ten. So, someone whose ideal weight is 100 pounds may require up to 40 grams of protein a day. On average, they probably only need about 30 daily grams of protein, which is 0.66 grams per kilogram, but we round it up to 0.8 or 0.9 grams because everyone’s different and we want to capture most of the bell curve.

People are actually more likely to suffer from protein excess than protein deficiency. “The adverse effects associated with long-term high protein/high meat intake” diets may include disorders of bone and calcium balance, disorders of kidney function, increased cancer risk, disorders of the liver, and worsening of coronary artery disease. Considering all of these potential disease risks, there is currently no reasonable scientific basis to recommend protein consumption above the current recommended daily allowance.

The “low” protein level in human breast milk (about 6 percent of calories) doesn’t mean adults only need that much. A 15-pound infant can suck up to 500 calories a day, but an adult who’s ten times heavier doesn’t typically consume ten times more food (5,000 calories). Although we weigh ten times more, we may only eat four or five times more. So, our food does need to be more concentrated in protein. Nevertheless, people tend to get way more than they need. See my video Do Vegetarians Get Enough Protein?.

Plant protein sources are preferable. See, for example:

But what about protein quality? Should we try to mix certain foods together at meals? See The Protein Combining Myth.

In health,

Michael Greger, M.D.