Changing Protein Requirements

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.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:

Do You Have to Combine Plant Proteins at a Meal?

All nutrients come from the sun or the soil. Vitamin D, the “sunshine vitamin,” is created when skin is exposed to sunlight. Everything else comes from the ground. Minerals originate from the earth, and vitamins from the plants and micro-organisms that grow from it.

The calcium in a cow’s milk (and in her 200-pound skeleton) came from all the plants she ate, which drew it up from the soil. We can cut out the middle-moo, though, and get calcium directly from the plants.

Where do you get your protein? Protein contains essential amino acids, meaning our bodies can’t make them so they’re essential to get from our diet. But, other animals don’t make them either. All essential amino acids originate from plants and microbes, and all plant proteins have all of the essential amino acids. The only truly “incomplete” protein in the food supply is gelatin, which is missing the amino acid tryptophan, so the only protein source you couldn’t live on is Jell-O.

Those eating plant‑based diets average about twice the estimated average daily protein requirement. Those who don’t know where to get protein on a plant-based diet don’t know beans… (Get it? 🙂 That’s protein quantity, though—what about protein quality?

The concept that plant protein was inferior to animal protein arose from studies performed on rodents more than a century ago. Scientists found that infant rats don’t grow as well on plants. However, infant rats don’t grow as well on human breast milk either. Does that mean we shouldn’t breastfeed our babies? Ridiculous! They’re rats. Rat milk has ten times more protein than human milk because rats grow about ten times faster than human infants.

It is true that some plant proteins are relatively low in certain essential amino acids. So, about 40 years ago, the myth of “protein combining” came into vogue—literally, in the February ’75 issue of Vogue magazine, as I discuss in my video The Protein Combining Myth. The concept was that we needed to eat so-called complementary proteins together (for example, rice and beans) to make up for their relative shortfalls. However, this fallacy was refuted decades ago. The myths that plant proteins are incomplete, aren’t as good as animal proteins, or need to be combined with other proteins at meals have all been dismissed by the nutrition community decades ago, but many in medicine evidently didn’t get the memo. Dr. John McDougall called out the American Heart Association for a 2001 publication that questioned the completeness of plant proteins. Thankfully, they’ve changed and now that “[p]lant proteins can provide enough of the essential and non-essential amino acids” and that we “don’t need to consciously combine…complementary proteins…”

It turns out our body is not stupid.

Our body maintains pools of free amino acids that can be used to do all of the complementing for us, not to mention our body’s massive protein recycling program. Some 90 grams of protein are dumped into the digestive tract every day from our own body to get broken back down and reassembled, so our body can mix and match amino acids to whatever proportions we need, regardless of what we eat, making it practically impossible to even design a diet of whole plant foods that’s sufficient in calories but deficient in protein. Thus, plant-based “consumers do not need to be at all concerned about amino acid imbalances…from the plant-food proteins that make up our usual diets.”


How did all of these myths surrounding protein come to be? Learn about The Great Protein Fiasco.

I cover protein quantity in my Do Vegetarians Get Enough Protein? video.

For more detail on the benefits of protein from plants, see:

Plant protein also doesn’t have the same effect on the cancer-promoting growth hormone IGF-1 that I discuss in the cancer section of my Food as Medicine presentation. Meat-heavy maternal diets may even affect the obesity rates and stress responses of their children, as I explore in my videos Animal Protein, Pregnancy, & Childhood Obesity and Maternal Diet May Affect Stress Responses in Children.

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:

Should Plant-Based Women Supplement with DHA During Pregnancy?

A systematic review of randomized controlled trials of DHA supplementation of pregnant and breastfeeding women failed to find any clear and consistent short- or long-term benefit for psychomotor, mental, visual, or physical development. Perhaps DHA supplementation during pregnancy has no effect because the body wisely protects the growth of the baby’s brain by drawing off of maternal stores of DHA, upregulating maternal DHA synthesis, and preferentially shuttling it to the fetus. But what if moms don’t start out with large maternal stores? In other words, maybe DHA failed to help women who were already getting enough, but perhaps women with very low intakes would benefit from DHA supplementation. My video Should Vegan Women Supplement with DHA During Pregnancy? explores the evidence available to date.

It’s interesting to note that, by 1978, researchers already were suggesting a plant-based diet as the diet of choice in the treatment of our number-one killer, heart disease, but babies breastfed by vegan moms had significantly less DHA in their bloodstreams, presumably because the moms had significantly less DHA in their breast milk.

The question is whether these differences are of any consequence. The growth and development of vegan and vegetarian born children are normal as long as they’re getting their B12, and “[t]here is no evidence that neural or intellectual functions are impaired.” In fact, the two studies we have on kids in vegetarian communities showed they had higher IQs, though that may be because their parents tended to be better educated. However, even though the kids seemed fine, that doesn’t rule out the possibility that there may be some “subtle differences…in visual or neural functioning.”

It would be interesting to compare the function of babies getting vegan breast milk levels versus general population levels. In one of the studies I profile in my video, it shows that vegans hit a level of 14, vegetarians 30, and omnivores 37. Another study compared 0 to 32, 64, and 96, and, though 32 worked better than 0, more than 32 didn’t add anything. This could explain why the general population at 37 doesn’t benefit from additional DHA supplementation. But what about down at 14? Most studies at that level show no advantage over 0, though one study found a benefit supplementing at as low as 5, but that doesn’t help us.

Just because babies breastfed by vegan moms have significantly lower DHA levels in the blood, that doesn’t necessarily mean they have lower levels in their brain, which is where it counts. What we need is a randomized, controlled trial in non-fish-eaters of DHA supplementation. Until then, it’s going to remain uncertain. So, what should pregnant and breastfeeding women who avoid fish do in the meanwhile? Low intake of DHA doesn’t “necessarily equate with fetal DHA inadequacy,” but new data suggest that some infants may not be getting enough and could benefit from their moms supplementing. Given this, I recommend pregnant and breastfeeding women on plant-based diets to follow the consensus guidelines to get about 200mg of preformed DHA from an uncontaminated source, like algae oil, which is probably the best combination for all women given the state of our world to minimize exposure to toxic pollutants such as dioxins, PCBs, and mercury. 


To gain a better understanding of why algae oil is better than purified fish oil, I encourage you to watch my video Should Pregnant and Breastfeeding Women Take DHA.

I’ve discussed concerns about pollutants in seafood during pregnancy in a number of my videos:

Finally, for more on taking long-chain omega-3s to protect your heart, see: 

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations: