I applaud you for co-authoring the book Proteinaholic and approaching the Super Human Radio interview with a combination of open-mindedness, thoughtfulness, and skepticism. You were a joy to listen to and I believe that we need more individuals such as yourself promoting the diversity of thought that Proteinaholic brings to light.
While the bulk of this letter addresses certain topics that we do not see eye-to-eye on, I want to start by highlighting the numerous points of agreement that were brought up throughout the hour interview. The irony with these, of course, is that they have little to nothing to do with protein.
1) All humans in the world are the same species and we will therefore have a fundamental dietary pattern that best suits our needs. At the core, this will be a whole-foods, plant-based diet without all the processed crap (can I say that on here?).
2) The typical Western population plagued with nutrition-related chronic diseases has an obsession with protein but not a protein deficiency. This is in contrast to the cold-shoulder given to fiber, micronutrients, and whole-foods, all of which are low to non-existent in the standard diet.
3) Yet, we cannot isolate specific nutrients easily. The scientific literature is limited by its inability to differentiate the sources of protein. As we both are aware, people buy and eat food, not nutrients.
4) Additionally, there is virtually no research looking at the exceptional – individuals such as yourself or the audience of Super Human Radio. Instead, the focus is on the sick Western population in general.
5) And educating them is difficult if for no reason other than that the media misrepresents every study they come across.
6) Finally, the human population has messed up our world. Current industrial agricultural and animal confinement practices are horrendous and serve only to deteriorate the environment and our health.
With that, the following is a rebuttal to some of the points you raised during the interview. I want to emphasize that this is science, not tribal warfare. The goal is to arrive at the best answer, rather than to win an argument. I'm proceeding in good faith, based on my belief that you and I are both serious people who care about science and human health. For the most part, everything is in chronological order based on the hour-long interview.
Does a hard-training athlete require more protein?
CLAIM: They require more calories, but not necessarily protein.
REBUTTAL: The collective agreement among reviewers is that a protein intake of 1.2-2.2 g/kg bodyweight is necessary to allow adaptation to training for individuals at or above their energy needs (Phillips et al; Tarnopolsky; Phillips & Van Loon; ISSN & ACSM position stands). I want to emphasize that this is not discussing “optimal” protein requirements, but rather the minimum to facilitate recovery and promote muscle growth. Additionally, requirements may increase further when the athlete is in a caloric deficit, with estimated needs to prevent muscle loss being 2.0-3.3 g/kg bodyweight.
If we were to briefly look at optimal amounts, then three protein-overfeeding studies (1, 2, 3) conducted by Dr. Jose Antonio provide a fascinating perspective. Although it is difficult to draw firm conclusions from this research because no other similar data exists, the preliminary findings show that consuming upwards of 4.4 g/kg of protein daily has no detrimental effect on blood chemistry or kidney function and leads to favorable changes in body composition via a loss of fat mass despite being in a caloric surplus. Importantly, these were all relatively short-term studies lasting eight weeks and we cannot assume that thing would be similar over a longer time period. However, Dr. Antonio is currently finishing up a year-long interventional study that should provide insight into this issue, and private discussions with him on the data so far have revealed no detrimental effects of this level of protein intake.
Do persistent organic pollutants (POPs) concentrate up the food chain?
CLAIM: All the chemicals and junk we create as a society gets concentrated in animal tissue. There is a large difference between plants and animals because most compounds are fat-soluble. Also, the United Nations determined that the concentration of these compounds is like 70,000 times as great in animals than grass.
REBUTTAL: It appears well established that the vast majority of POPs are lipophilic and bioaccumulate up the food chain. I highly recommend reading the 1997 study by the Arctic Monitoring and Assessment Program, called Arctic Pollution Issues: A State of the Arctic Environment Report. It found that caribou in Canada’s Northwest Territories had as much as 10 times the levels of polychlorinated biphenyl (PCB) as the lichen on which they grazed; PCB levels in the wolves that fed on the caribou were magnified nearly 60 times as much as the lichen. This report embodies the bioaccumulation issue, although it does also clearly show values far less than the stated 70,000-time magnification.
But where did the POPs come from to begin with? The arctic is a region that resembles the world before modernization, mainly because it is a difficult area to inhabit. Yet, even with its isolation, the aforementioned report specifically states that “the main contaminants of concern are: organochlorine pesticides (e.g., HCH) and their metabolites from agricultural activities/practices; industrial chemicals (e.g., PCBs); and anthropogenic and natural combustion products, e.g. chlorinated dioxins/furans and polycyclic aromatic hydrocarbons (PAHs).” Indeed, the report also states that “the levels of POPs cannot be related to known use and/or releases from potential sources within the Arctic and can only be explained by long-range transport from lower latitudes.”
So while animals may contain more POPs, it is reasonable to hypothesize that that this is primarily because of industrial practices such as those used in agriculture. Similarly, when looking at human exposure, animals that we consume may be a primary source of POPs, but environmental exposure and the consumption of agricultural crops no doubt play a substantial role as well. We live in an environment that is plagued by chemicals – something we both agree on. Unfortunately, this environment makes POP exposure ubiquitous, and we must acknowledge the role that agriculture and plants play in human POP exposure, both directly and indirectly through the food chain, rather than single out animal foods as being particularly harmful.
Is plant protein more efficient than animal protein?
CLAIM: It’s 16 times more efficient to get protein from plants than animals.
REBUTTAL: This claim is difficult to approach because it lacks a lot of very important context, such as what defines efficient and which plants/animals are being referred to. I am going to focus on the nutritional aspect because that is what has the largest impact on our health and is the implied context of our discussion. I recognize that a different conclusion than follows could be reached if we evaluated the environmental impact of where the protein is obtained from, but I have not researched this issue significantly and am not comfortable forming conclusions around it.
Coming back to context, not all sources of protein are the same, even within the broad categories of plants and animals. Therefore, this argument could go in several directions. To keep things focused and simple, I used the USDA food database to look up the protein content of a standard cut of meat – braised beef top round steak. I then used the nutrient search function within the database to list all foods within a given category by protein content per 100 grams.
Vegetables and Vegetable Products
The most protein-heavy product to show up under the “vegetables and vegetable products” that people actually eat (I’m ignoring the dried spirulina, yeast extract, and freeze-dried chives) is boiled soybeans, which boast 12 grams of protein per 100 grams of beans. By comparison, the beef steak contains 36 grams of protein per 100 grams of steak. The next vegetable after soybeans is cooked pinto beans with 9 grams of protein per 100 grams of bean. A variety of other beans follow suit, with the first non-legume vegetable being raw kale, with 4 grams of protein per 100 grams of food.
It is well accepted that legumes are one of the best plant-based sources of protein. Yet, even they contain a maximum of one-third the protein provided by a cooked piece of flesh. For starchy and fibrous vegetables, meat wins by 9-fold. Moreover, if we were to look at these items on a per calorie basis, then the 100 grams of beef is about 190 kcal and 36 grams of protein. However, to obtain the same 36 grams of protein you would need to consume about 420 kcal worth of soybeans or 450 kcal of kale.
Nut and Seed Products
When we change the category to “nut and seed products,” hemp and pumpkin seeds come in first place with about 30 grams of protein per 100 grams of seed (assuming you don’t eat roasted cottonseed kernels). Walnuts, almonds, and pistachios are next with about 21 grams of protein. These values are certainly better than the legumes and appear competitive with beef until you consider that the caloric requirements to obtain them is ridiculous. Compared with beef’s 190 kcal for 36 grams of protein, one would need to consume 640 kcal of hemp seeds, 690 kcal of pumpkin seeds, or 980 kcal of almonds to obtain the same 36 grams of protein. Delicious? Yes. Realistic? No.
Cereal Grains and Pasta
Woot! Coming in at numero uno, under the category of “cereal grains and pasta,” is my personal favorite grain – oats (I’m ignoring wheat germ and the curious entry of protein-fortified spaghetti). Whole oats and oat bran both contain about 17 grams of protein per 100 grams of grain. Wild rice is next at 15 grams of protein, followed by quinoa and durum wheat at 14 grams. Despite my love of oatmeal, it still pities in comparison to beef. One would need to eat 830 kcal worth of oats to obtain the same 36 grams of protein that 190 kcal of beef steak provides.
The above isn’t to say that plants don’t contribute nutrition to the diet, because they do. Plants are an excellent source of fiber, starch, healthy fats, and numerous micronutrients and bioactive compounds. However, they are not an excellent source of protein. Of course, this only deals with protein quantity. Let’s now look at protein quality.
As I’m sure you are aware, proteins are digested into their constituent amino acids, which then participate in a variety of bodily processes. One of the most important of these processes is their role as signaling molecules for muscle protein synthesis (MPS) and as building blocks for muscle growth. A very recent review comparing the anabolic response of plant vs animal proteins was published last year in the journal, Nutrition. Based on literature using the contemporary stable isotope amino acid tracer methodology to directly assess the capacity of various dietary proteins to stimulate postprandial MPS, the authors come to a variety of notable conclusions that I have listed below.
1) Animal-based proteins such as dairy, eggs, and meat have a digestibility that exceeds 90%, whereas plants such as maize, oat, bean, pea, and potato range from 45-90%. In fact, it is only after plant proteins have been purified into protein powders free of other anti-nutrients that interfere with digestibility (e.g., soy and pea protein isolates) does the protein digestibility rival that of meats.
2) Amino acids derived from soy and wheat are more readily converted into urea compared to dairy, ultimately lowering the potential of these protein sources to stimulate MPS. Why more urea is formed is not entirely clear, but may relate to the relative lack of specific essential amino acids that leads to an unfavorable amino acid mixture for gut protein synthesis, which leads to more of the free AAs to enter the portal vein to hepatic tissue and be converted into urea.
3) Two notable amino acids lacking in plant-based proteins are lysine and methionine. The food combination traditions of historically vegetarian societies (e.g. grains combined with legumes) serves to illustrate the extra effort required to overcome this deficit.
4) Although not necessarily lacking in plant-based proteins, leucine content is lower than in animal-based proteins. Leucine plays an important role in stimulating mTOR and promoting muscle growth and adaptation to stress. Most plant-based sources have a leucine content of 6-8%, whereas animal-based protein sources tend to have a leucine content in the range of 8.5-9% and >10% in the case of dairy proteins.
5) Despite the notable differences in protein quality, research suggests that the ingestion of greater quantities of plant-based proteins may compensate for the lower essential amino acid content, thereby improving the potential of plant-based proteins to support skeletal muscle mass gains. Evidence also suggests that the ingestion of higher amounts of protein may reduce the proposed differences in the capacity of different protein sources (plant vs. animal) to modulate the gains in skeletal muscle mass during prolonged exercise interventions.
a. Side note: both these points are moot in light of your recommended protein intake of 0.8 g/kg.
6) Finally, observational evidence has suggested that “a greater proportion of daily protein intake derived from animal- vs. plant-based sources is associated with better muscle maintenance in older and more clinically compromised individuals (83–86). For instance, long-term vegetarianism in older women has been reported to compromise muscle mass maintenance when compared with consumers of an omnivorous diet (18.2 vs. 22.6 kg LBM) (85).”
Finally, I’m sure we can both agree that one of the best plant-based protein sources is soybeans. Yet, two studies have investigated the use of supplemental foods obtaining protein from soy compared to whey protein or skim milk in the treatment of moderate and severe malnutrition of children. In both studies, whey protein is superior for promoting recovery and reducing mortality rates.
Are soybeans more nutrition than beef?
CLAIM: Soybeans have a lot more nutrients in them than cows.
REBUTTAL: If we use the USDA food database to compare boiled soybeans to up braised beef top round steak, it becomes clear that both foods have advantages over the other. Soybeans are a better source of fiber, carbohydrates, potassium, magnesium, vitamin C, thiamin, and folate, while beef is a better source of protein, iron, zinc, niacin, vitamin B6, and vitamin B12. I could mention how other parts of beef, such as liver, absolutely dominate almost every other food in existence from a nutritional standpoint, but it is not entirely relevant considering that most people dislike organ meats.
Is trypsin a limiting factor in soybean digestibility?
CLAIM: Only 35% of the American population produces trypsin that makes soybeans digestible. This wasn’t a claim by you, Howard, but rather one made by Carl during your discussion. I felt it necessary to address since I don’t agree with it.
REBUTTAL: Tryspin is a digestive enzyme formed in the small intestine that acts to break down protein. As far as I am aware, all humans make trypsin. However, there are such things called trypsin inhibitors that reduces trypsin’s biological activity. Trypsin inhibitors are present in soybeans, but are easily inactivated by heat treatment (i.e., cooking). Additionally, many studies on this topic have been performed in animals, but some evidence suggests that human-based trypsin is more resistant to inhibition than animal-based trypsin. Thus, they don’t appear to be of concern in a normal human diet.
Can we isolate Blue Zone longevity to dietary practices?
CLAIM: The longest living populations such as the Blue Zones eat a high-carbohydrate, low animal diet.
REBUTTAL: I’m sure we can both agree that correlation is not causation, and more so that it is impossible to isolate certain dietary habits as the reason for the longer lifespans of the blue zone populations in comparison to Western societies. For instance, the Blue Zones investigators reported that “some lifestyle characteristics, like family coherence, avoidance of smoking, plant-based diet, moderate and daily physical activity, social engagement, where people of all ages are socially active and integrated into the community, are common in all people enrolled in the surveys.” This is in stark contrast to the chronically stressed, sedentary, and socially isolated Westerner who eats a nutritionally void and calorically dense diet based on highly processed grains, meats, and oils.
There is little doubt that diet does play a role in the longevity of the Blue Zone populations, but we cannot conclude that this diet would have similar effects in a population where the other lifestyle factors are so drastically different. There also remains a possibility that consuming more meat and more protein would further extend life among these populations when combined with their lifestyle habits.
To illustrate this above point, what if the Blue Zone populations consumed more glycine-rich protein sources such as collagen, bone broth, and offal? Animal research supplementing glycine into the diet has indeed found similar longevity benefits as studies that restrict calories or protein – without the restriction part being necessary. Indeed, evidence has suggested that the "harmfulness" of animal protein could actually be caused by the insufficient glycine intake on high-methionine diets that include muscle meat, milk, and eggs.
Finally, living a long life is not the same as having a life worth living. That is, looking solely at longevity misses the arguably more important factor of having a high quality of life while aging. As mentioned previously, several studies have associated increased daily protein intake with better muscle mass maintenance in elderly individuals. Sarcopenia is a known problem among the aging population and results in a considerably reduced quality of life and considerably increased risk of disease. Importantly, loss of muscle mass may then impair the ability to be active and exercise, thereby further reducing muscle mass in a viscous cycle. Now, certainly there is an individual component here. For me, living an extra 5 or even 10 years is not worth it if I must spend that time confined to a wheelchair without my independence.
This of course raises the question of how we can both live long and retain our muscle mass, physical function, and independence. It may not seem possible at first glance, since a reduction in mTOR and IGF-1 and an increase in AMPK signaling are the hallmarks of longevity but also promote muscle catabolism. However, a recent review article published in Aging Cell argues otherwise.
In this review, the authors conclude that “optimizing dietary restriction (DR) or using DR mimetics in combination with amino acid administration may be critical interventions to help attenuate [skeletal muscle] SkM loss with advancing age, while enabling healthy aging.” This conclusion was based on experimental research in animal models showing that undertaking dietary restriction that is protein-rich reduces fat mass while sparring muscle mass and is associated with reductions in circulating insulin and IGF-1 levels, thus alluding to potential benefits for lifespan without risk of muscle loss. It must also be kept in mind that one is not constantly eating and the Blue Zone populations have defined meal times with adequate bouts of fasting between and overnight. It is plausible that one could eat a protein-rich diet to maximize muscle growth during a feeding window and then proceed to fast for 12-18 hours overnight on a daily basis, thus providing ample time for AMPK and autophagy to do their cellular clean-up duties observed during chronic caloric restriction.
Do nonhuman primates prove we can thrive on low-protein diets?
CLAIM: If you look at comparative anatomy of humans and other animals, we are much more related to chimps. We are hind-gut fermenters and should be eating plants. We are basically fruitivores – fruit eaters. For instance, if you look at the small intestine length compared to body length, carnivores and omnivores at 4-6 times while herbivores at 10-12 times. Humans are 10-11 and thus in the herbivore range.
REALITY: Unlike humans, orangutans and gorillas are fabulous hindgut fermenters boasting huge colons full of cellulose-degrading bacteria that turn otherwise indigestible food into energy. If we had an anatomy like them, then we should have no problem surviving on twigs and bark. But of course, our anatomy is different enough to make us a different species. The chimpanzee gut is dominated by the colon, while the human gut is dominated by the small intestine – a proportional shift that indicates we’re better equipped to handle dense foods like meat and cooked starches than bulky plant roughage that requires bacterial fermentation. Specifically, the human small intestine is twice as long as that of orangutans, gorillas, and chimpanzees, while our colon is less than half their size.
Source: Milton K. Nutritional characteristics of wild primate foods: do the diets of our closest living relatives have lessons for us? Nutrition. 1999; 15(6): 488-98.
Regardless, other primates are far from veggie-munching hippies. For instance, because gorillas eat over 40 pounds of vegetation in a day, they consume anywhere between 17-31 % of their calories as protein. Moreover, chimps eat enough meat to leave isotopic animal-protein evidence in their hair and bone.
CLAIM: The Recommended Daily Allowance (RDA) for protein of 0.8 g/kg is the optimal value.
REALITY: The RDA was established by the Institute of Medicine and is defined as “an estimate of the minimum daily average dietary intake level that meets the nutrient requirements of nearly all (97 to 98 percent) healthy individuals.” This amount was based on the results of all available studies that estimated the minimum protein intake necessary to avoid a progressive loss of lean body mass as reflected by nitrogen balance.
However, we have research dating back to at least 2001 that shows that this amount is not sufficient for elderly adults. In fact, a very recent review paper published in 2015 out of Deakin University concludes that “recent metabolic and epidemiological studies indicate that the current Recommended Dietary Intakes for protein appear to be inadequate for maintenance of physical function and optimal health in older adults. The current body of evidence indicates that a dietary protein intake of at least 1.2 g/kg/day is required to maintain optimal muscle function in older people.”
This conclusion falls nicely in line with the 2013 position paper from the European Union Geriatric Medicine Society, which states that older adults require at least 1.0-1.2 g/kg bodyweight of protein to support good health, promote recovery from illness, and maintain functionality. For adults with chronic diseases, their recommendation increases to 1.2-1.5 g/kg.
Additionally, The Society for Sarcopenia, Cachexia, and Wasting Disease convened an expert panel to develop nutritional recommendations for prevention and management of sarcopenia, which was published in 2010. The panel recommended that “older persons ingest between 1.0 and 1.5 g of protein/kg/d.”
Finally, one of the largest elderly cohorts to date is the Health, Aging, and Body Composition (Health ABC) Study. Over a 3-year follow-up period among 2066 community-dwelling men and women aged 70-79 years, total and animal-based protein consumption, but not plant-protein consumption, significantly predicted increases in total lean body mass and appendicular lean body mass. This was after adjustment for age, sex, race, study site, total energy intake, baseline lean mass or appendicular lean mass, height, smoking, alcohol use, physical activity, oral steroid use, prevalent disease, and interim hospitalizations. Specifically, participants in the highest protein quintile lost 43% less lean body mass and 39% less appendicular lean mass over the 3-y follow-up than did those in the lowest protein quintile. The lowest quintile consumed 0.7 g/kg while the highest quintile consumed 1.1 g/kg.
It is also important to note that the RDA relies on nitrogen balance, which has several limitations. For instance, variations in overall body nitrogen and amino acid metabolism can lead to a change in nitrogen balance, with or without a change in protein intake. If excretion is changing without a change in intake, it becomes difficult to determine whether or not the effect is due to the dietary protein intake, because this method is basing conclusions on specific dietary protein intakes. Also, testing requires five to ten days of adaptation to each level of amino acid by a participant, and complete collection and quantification of all sources of nitrogen excretion (mostly in urine and feces, but also sweat) is difficult.
An alternative method for studying protein needs is the indicator amino acid oxidation (IAAO) method. This method is based on the concept that when one essential amino acid (EAA) is deficient for protein synthesis, then all other EAAs, including the “indicator” amino acid, will be oxidized. This is because the deficient amino acid becomes the limiting step in protein synthesis. This method is non-invasive, doesn’t require a week of adaptation at a set protein level, and can be measured through breath and urine samples.
Using the IAAO method, it has been shown that the current RDA is not sufficient to meet the protein requirements of elderly women or men aged over 65 years, of women aged over 80 years, or of young men in their twenties. According to these studies, the RDA for both young and elderly men and women should be 1.2-1.3 g/kg.
Of course, nearly all of this research deals with elderly or sedentary populations. I have already addressed the protein requirements of young athletes. Briefly, the collective agreement among reviewers is that a protein intake of 1.2-2.2 g/kg bodyweight is sufficient to allow adaptation to training for individuals at or above their energy needs (Phillips et al; Tarnopolsky; Phillips & Van Loon; ISSN & ACSM position stands). Moreover, Dr. Jose Antonio has published three studies thus far that show no detrimental effect of protein intake above 3 g/kg. In fact, these studies show that increasing protein intake to 4.4, 3.4, and 3.3 g/kg has no detrimental effects on blood chemistry or kidney function and leads to a loss of fat mass despite being in a caloric surplus.
On the other side of the spectrum, the renowned George Bray, MD of the Pennington Biomedical Research Center confined young, sedentary, healthy men to a metabolic ward for two weeks while being fed 40% more calories than they required, with protein being 0.9, 2.3, or 4.0 g/kg of protein per day. Despite being in a 40% surplus, the RDA-level protein group lost muscle mass while the other groups gained muscle mass.
Overall, there is ample research published over the past 30 years that clearly shows the RDA for protein consumption is not the optimal amount of protein to be consuming. In fact, the research suggests it isn’t even the minimal amount to prevent muscle loss. While there is controversy over what should be considered optimal, the research is clear that both young and elderly individuals appear to require at least 1.2 g/kg of protein daily.