Our Preoccupation With Protein Intake

The data on high protein diets, bars, supplements, and powders will surprise you

I listened to The Daily podcast this week, “How America Got Obsessed With Protein,” which helped explain how this macronutrient frenzy has progressed to an unprecedented fever, but also had significant errors. While I had written about this topic in SUPER AGERS, it was time to review all the data available, for both efficacy and safety, of high protein intake. That’s what this edition of Ground Truths is about.

I will come back to this important Figure below later in the post, from an important study in both mice and people, demonstrating that high protein intake accelerated atherosclerosis and increases cardiovascular risk, and provided the underlying mechanism. In contrast, The Daily podcast stated: “Well, it’s unlikely that eating too much protein is actually going to harm you. Unless you have a specific kidney issue, we can eat a lot of protein. And it’s not going to be bad for you.” It turns out there’s no shortage of data to refute that assertion made by the New York Times (which produces The Daily).

Let’s get into this topic by answering 3 questions:

1. What is driving the protein obsession?

2. What are the data for high protein intake health benefits?

3. What are the safety concerns regarding high protein consumption?

1. Driving The Protein Obsession

The most recent published 2024 International Food Information Council annual survey of Americans found that 71% want to increase their protein intake, more than any other dietary constituent or vitamin. That number for protein was 52% in the 2022 survey. The number of Google searches for “high protein” peaked in 2025.

It’s no wonder. Social media is chock full of protein promoters. A search of TikTok for “200 grams of protein a day” gets dozens of instructional videos. A survey of non-professional athletes taking protein supplements found that 40% get their information from social media. The Daily asserted that there are two main influencers driving the high protein craze:

“So the protein is going to be a substance that helps you improve your health, and not only lose weight, not only gain muscle, but also being the best physical version of yourself. And the two biggest and most influential names here are Peter Attia and Andrew Huberman. And these two guys are really extraordinarily influential in the nutrition space right now, the wellness space……Protein is a big part of it for both of them.”

The podcast centered on the wildly successful David bars (pictured below), which are promoted by these 2 influencers who each have a stake in the company. The bars are unique for packing in 28g of protein into 150 calories which are on track to sell $180 million in 2025. The method for achieving this high density, lower calorie product hinged on using EPG, “a modified plant fat that moves through your digestive system mostly undigested.” One problem with the David bar is that, by definition, it is an ultraprocessed food, i.e. not exactly rigorously perfected protein as proclaimed on the website). David Protein, the David bar company, bought Epogee, which makes EPG, to own the patent rights, insure supply, and lock out competition. David Protein recently launched David Cod, which sells four 6 oz pieces of frozen cod for $55 and plans to become a/the platform for protein.

From the David Protein company website, the image of a sculpted body holding a David Bar

The pervasive call for higher protein intake stems from the assertion that people are not getting adequate amounts in their diet, namely the 0.8 g/kg/day recommended by the National Academy of Medicine and the World Health Organization. Yet the most recent data from USDA says the federal protein recommendation is exceeded by more than 55% of men and 35% of women. Peter Attia advocates for 2.2 g/kg/day (or 1 g/lb/day) of protein intake in his book Outlive. That translates to almost 3-fold the established recommendation. Attia “declined multiple requests to comment” in a recent New York Times piece entitled, “The More Protein, The Better?” written by Alice Callahan, who has a PhD in nutrition. Regarding the need to increase protein intake 2-3 fold per day, Stuart Phillips, a leading expert on protein, energy, and building muscle mass, who is a professor at McMaster University in Canada, said “It’s baloney. But there’s a generation, particularly young men, and now an increasing number of young women, who are absolutely brainwashed by what they hear online.”

Some of the confusion on the right protein intake amount depends on the physical activity of the individual, for example sedentary vs weightlifter. Phillips, who has published extensively on this topic, recommends higher protein intake for weightlifters at 1.2 to 1.6 g/kg/day which is based on the data we’ll review next.

2. The Data for High Protein Health Benefits

In the Table below, I pulled together all the published meta-analyses and systematic reviews that I could find on the topic of high protein intake. The senior author of the top 2 is Stuart Phillips. The number of randomized clinical trials (RCTs) and the number of participants (N) is shown along with the relevant features of the participants and the primary conclusions. The endpoints of these trials included muscle mass, muscle strength, and lean body mass.

Simply put, there are no data to support more than 1.6 g/kg/day of protein intake. Some of these studies were in older adults with mixed data (Nunes study no benefit for older group; ten Haaff no benefit age 50+ over resistance training; Liao benefit in older men on top of resistance training). Likewise, the data are mixed for overweight and obese participants. The findings across all the studies, most of which are quite small in sample size, show marked inter-individual variability. The design and the analysis of the trials are compromised by lack of controlling for calories in the diet, physical activity, and many other confounding factors, along with flaws of interpretation.

The Morton study is the most widely cited, but the main graph shown below is problematic. The y-axis is for the change in fat-free mass (FFM) and the x-axis plots total protein intake.

As aptly pointed out by Nassim Taleb and others on X, the vertical line drawn down to 1.6 g/kg/d is an illusion or myth, without statistical basis. If you take away the vertical and horizontal lines from the graph, you see it is a contrived regression, a scatterplot (below), that does not support any optimal level of protein intake. Moreover, the P value for the regression is 0.079, which is not significant.

Replot of the data points without the lines by Nassim Taleb showing it is actually a scatterplot; removing 1 data point would markedly skew the p-hacking result, which was not significant.

What about the strong recommendation for high protein in older adults? In the 50+ group, as reviewed by ten Haaf and colleagues, the randomized trials show no benefit of high protein on top of resistance training compared with resistance training alone (the control group) for improved lean body mass and there is no heterogeneity. The boxes below are all aligned with 0.00, no difference) for the 12 trials reviewed.

So we don’t even know at this point whether resistance training alone is enough to improve lean body mass, let alone what is the optimal dose of protein intake in older adults. Despite much uncertainty, in Europe the recommendation is for people over age 65 years to increase their protein intake by at least 1/4th, or from 0.8 g/kg/d to about 1.2 g/kg/d.

Higher protein intake has been thought to promote satiety and help people reduce weight but even that’s still unclear. Multiple studies have shown the higher the protein intake, the greater the number of calories (energy) consumed.

2. Safety Concerns Regarding High-Protein Intake

There are many observational studies that have raised the safety concerns for high-protein intake, particularly derived from animal protein, for increased risk of type 2 diabetes, cardiovascular disease, and higher all-cause mortality. A prospective study of ~44,000 women in Sweden followed for 15.7 years found an association of high-protein diet with heightened cardiovascular risk. In 2,441 men aged 42 to 60 years followed for 22 years, there was increased heart failure among those who had a high protein diet, especially if it was predominantly animal derived. We’ve long known that high protein intake is dangerous for people with kidney disease, present in 1 of 7 adults, but 9 of 10 people with reduced kidney function are unaware of it. A higher risk of all-cause death was noted in a secondary analysis of a randomized diet trial. Of course, a problem with these studies is that they typically rely on food diaries or memory of the participants.

In mouse models of 25 diets, high protein diets were linked with less longevity and healthy aging indexed to activation of mTOR (more on this below). Consistently it has ben found that low—not high—protein diets are associated with longevity and healthy aging in animal model experiments.

A review entitled “A Word of Caution Against Excessive Protein Intake” concluded: “Although high dietary protein intake can increase muscle mass during resistance exercise training in young adults, a high-protein diet does not have clinically meaningful effects on lean mass or muscle mass during weight maintenance, weight gain or weight loss. Moreover, increasing protein intake is not without risk and can have adverse effects on metabolic function.” Another expert review concluded: “habitual high-protein intake, without marked carbohydrate and energy restriction, is associated with increased cardiometabolic disease risk.”

Now let’s get to recent work that helps illuminate the risk. A leader in this field is Babak Razani and his team at Washington University. In 2020, in the experimental model, Razani and colleagues determined that high protein was shown to activate the mammalian target of rapamycin (mTOR) in macrophages, which promoted atherosclerosis progression by inhibiting the clearance of damaged mitochondria (mitophagy). More recently, the same group probed this high protein atherosclerosis question in mice and people . The essential amino acid leucine (essential amino acids are not manufactured in the body, only obtained from ingestion) was found to be the culprit, driving atherosclerosis (simplified graphic below). Please also refer to the top Figure of this post that extrapolates the increased risk of atherosclerosis and cardiovascular disease from the data, showing up at protein intake of 1.5 g/kg/day.

This work supports leucine as a casual link for high protein intake and promotion of atherosclerosis via activation of mTOR. The studies in people were small with acute challenges of very high protein intake (from 22% to 50% of energy) and resultant high blood levels of leucine, changes in their circulating monocytes with mTOR activation, also flanked by the striking increase in inflammation and atherosclerotic plaque in the arteries of mice (studies you can’t easily do in humans).

This leucine discovery is important because leucine is one of the 3 branched chain essential amino acids that is widely used as a supplement by people training and athletes and one with putative anti-aging properties. Which is remarkable since potently activating mTOR is just the opposite of rapamycin (that blocks mTOR), a drug that many longevity influencers take! Remember that leucine is one of the 3 essential branched chain amino acids which are unique since they are primarily metabolized by muscle, not liver. So leucine may be considered pro-inflammatory and a bad actor even though it is also tied to building muscle mass. I wonder how many of the longevity influencers are taking both leucine supplements and rapamycin.

The conditionally essential amino acids refer to those needed in certain conditions from outside sources while the non-essential amino acids are ones the body can synthesize.

There are other recent experimental model studies that extend these safety concerns. A metabolite of histidine (imidazole propionate, imP), another essential amino acid, from bacteria in the gut microbiome, has been shown to directly (causal) induce atherosclerosis, again through the same mTOR activating, pro-inflammatory mechanism as leucine (schematic below). People who eat diets of fish, poultry, leafy vegetables, whole grains, nuts and fruits have lower blood levels of ImP.

Another recent study found that high protein intake shortened lifespan and accelerated aging in a mouse model of accelerated aging (progeria)

Concluding Remarks

The obsession with increasing protein intake is without basis. 85% of the US population consumes more than the 0.8 g/kg/day recommended daily intake (RDI) and nearly 25% are consuming twice the RDI (Figure). IOM is Institute of Medicine, now named National Academy of Medicine.

The body of evidence about protein does not provide support very high protein intake, certainly not in excess of 1.6 g/kg/day, twice the recommended dietary allowance. Even that high level is not adequately substantiated for the reasons reviewed above. I cannot find any high quality data (e.g. from any randomized trial among hundreds that have been done) to substantiate the ~3-fold RDI (1g/lb/day) recommendation of the very high protein promoters.

There are 2 key principles to keep in mind about protein intake. For one, unlike carbohydrates and fat, there is no way to store protein in the body. In the excellent new book Food Intelligence by Kevin Hall (a leading US nutrition expert) and Julia Belluz (due out in September) that I reviewed, Stuart Phillips points out: “You can eat a ton of protein. You can digest a ton of protein. But the key question is: How much can you use? And we don’t have a way of stocking away extra amino acids.”

The more protein you take in beyond what can be used that day, the more is wasted. The nitrogen from amino acids is removed to form ammonia, converted to urea, and excreted in your urine.

Habitual or chronic high protein intake is associated with epidemiological evidence of harm, and, at high doses, the studies I reviewed raise the concern about pro-inflammatory effects and increasing cardiovascular risk, promoting the process of atherosclerosis. The essential amino acid leucine has been identified as the main culprit, which is rich in animal products such as meat, eggs, and dairy products. Although not as high in density, plenty of leucine intake can be derived from vegetables such as beans, seeds and nuts. There is no reason to take leucine supplements, which could be harmful.

The second point is that eating extra protein does not build muscle. Protein doesn't power muscle. I’ll cite the funny post by Nassim Taleb that helps bring this point home.

Resistance training is the principal driver for building muscle mass and strength, not high protein intake. Not growth hormone (see my recent post on peptides).

I’m not a nutrition scientist. Neither are the two main influencers of very high protein intake who both have stakes in companies that sell protein supplements. Besides my citing of Stuart Phillips and Kevin Hall, who are highly regarded authorities, here’s Prof Ethan Balk on faculty at New York University on the 1 g/lb/day (2.2 g/kg/d) protein intake: “The bodybuilding community kind of swears by it. But there’s been less, if any, support from research on that.” Prof Luc van Loon at Maastricht University in the Netherlands on increasing protein intake for people strength training said: “Tripling it is far more than most people require.” Or Prof David Church at University of Arkansas for people who want to build muscle, 1.5 to 2 times the RDI can be supported, “Beyond that amount the effect of protein on muscle gain kind of plateaus.”

Many people ask me what do I do? As I wrote in SUPER AGERS, “If I’m going to be old, I’d rather be strong and old!” I’m a septuagenarian and do strength training at least 3 times per week, for 30 minutes or more, including use of bands, free weights, push-ups, chin-ups, and deadlifts. I weigh 180 lbs which is just less than 82 kg. It’s very easy for me to get 82 g of protein in a day with a largely plant-based Mediterranean diet, eating Greek yogurt for breakfast, nuts for snacks, and a salad with salmon or tuna fish or beans for dinner. When I occasionally add up the protein I take in during a day, it is typically 100 to 120 g, which is equivalent to 1.2 to 1.4 g/kg/d. It would be an arduous struggle for me to eat 180 g of protein a day (the 1g/lb/day, an unfounded recommendation). And that excess protein would just get excreted.

There’s simply no need or evidence to be preoccupied with your protein intake. While it is clearly a current craze and a big revenue source for protein promoter companies and individuals, it is not substantiated. I hope you will consider this review useful and that it may help liberate you from any fixation on high protein intake.

A quick poll (yes, muscle mass is a typo below; Substack gives very limited space for characters in the choices)

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