Should You Eat Less Protein?

High Protein Foods on wooden table. Top view

Over the past several years, I’ve noticed a subtle shift in the way the media discusses dietary protein, with many experts promoting lower intakes. The push for lower intakes hasn’t only come from the mainstream crowing about red meat and colon cancer. Many voices from the alternative health communities are urging a reduction in protein. Even the ancestral health community counts among its ranks protein skeptics.

Am I one? I’m not sure. In past posts, I’ve discussed how my own tastes have changed, going from eating high protein to more moderate amounts.

Today I’m addressing the standard arguments levied against high protein intakes. Hopefully, we can get to the bottom of the issue.

High protein diets stress the kidneys.

While it’s true that people with existing kidney damage or disease must limit protein intake, this isn’t the case in healthy people. Even type 2 diabetics with good kidney function can safely eat a long-term high-protein diet. If anything, higher protein intakes protect against kidney disease by making it easier to avoid obesity.

High protein diets exceed your capacity for ammonia detox.

Protein metabolism begets ammonia, a toxin. The liver usually converts ammonia into urea, which is safely expelled through the urine. The average human can handle about 230 grams of protein before ammonia-urea conversion tanks. After that, ammonia lingers. If your liver health is compromised, or your protein intake exceeds your ammonia detox capacity, ammonia toxicity can ensue.

Acute ammonia toxicity is neurotoxic, actually causing your astrocytes to swell. Rabbit starvation, which afflicted Arctic explorers living exclusively on lean protein (rabbits) and causes nausea, diarrhea, and eventually death, might derive from ammonia toxicity. A subtler, lower-grade ammonia toxicity likely exists in people with chronically-high intakes of protein. The dangers are mostly theoretical but based in physiology—ammonia is a toxin, and there is a limit to how much of it we can convert to urea.

High protein diets create toxins in the gut.

Sufficiently high intakes of protein can exceed the gut’s capacity to absorb it. The protein then passes on to the colon, where colonic bacteria ferment it and produce metabolic byproducts like ammonia, indoles, and phenols. As many of these compounds can have toxic effects, some have suggested that excess protein fermentation produces a toxic gut environment.

In one study, researchers gave subjects either a high protein diet, a low protein diet, or a normal protein diet. They analyzed the fecal water of each group for evidence of protein fermentation and ran a series of tests to determine the toxicity of each batch of fecal water. Surprisingly, while the high protein fecal water had elevated markers of fermentation, it was not toxic, and elevated protein fermentation metabolites actually correlated with lower cytotoxicity.

High protein diets give you cancer.

Vegans love citing the T. Colin Campbell research from the China Study, which appeared to show that high intakes of protein caused increased cancer deaths. While adequate intakes of protein (from casein) promoted the growth of existing tumors in those rodents, it also protected against the mutagens that cause the initial appearance of tumors. Protein was protective against cancer until they had it, at which point it accelerated the cancer’s progression. Rodents on the low protein diet were more susceptible to getting cancer after aflatoxin exposure. Once the rodents already had cancer, low protein was protective against further growth.

More accurate: adequate protein protects against the initiation of cancer (and probably other maladaptive ills), but patients with cancer should limit it. That makes sense. Context is everything.

Extra protein just converts to glucose.

Through the process of gluconeogenesis, we can convert protein into glucose. This has led some folks to believe that eating “extra protein” is like eating a piece of chocolate cake. So, does a high protein diet spike glucose levels? Is eating more protein just like cramming in extra sugar?

In one study, type 2 diabetics ate half a pound of steak (50 grams protein) and nothing else for breakfast. Compared to the control group who just had water, 50 grams of protein had almost no effect on glucose levels, adding just 2 grams to circulation. In another older study, eating up to 160 grams of protein in a single meal had no effect on blood glucose.

On the contrary, high-protein diets have been shown to improve glucose control in the population most at risk from high-carb intakes: type 2 diabetics.

High protein is unnecessary.

Protein is the most expensive macronutrient. In the wild, it takes the most energy to acquire. In the civilized world, it costs the most money to purchase. If we don’t need large amounts of protein, it makes sense to reduce our intake.

Many people lifting weights and cramming down protein shakes likely are eating more protein than they need. The more advanced you are as a lifter, the less protein you need. Beginners gain weight like crazy; experienced lifters do not.

Advanced lifters are closer to their genetic muscle ceiling. There’s less room to grow, so they grow more slowly, and muscle protein synthesis actually declines. Plus, their muscles have become more resistant to exercise-induced breakdown. It takes more to damage them, and there’s less to recover from. Overall, experienced lifters are more efficient with their protein and can maintain nitrogen balance at 1.05 g/kg. If they want to gain muscle, 1.8 grams per kg (which is much lower than most people assume) seems to be the absolute ceiling for natural lifters. After that, the benefits level off, and you’re just wasting protein.

Interestingly, endurance athletes require more protein than bodybuilders to remain in nitrogen balance.

High protein diets increase IGF-1 signaling.

IGF-1 is an important compound that helps us build and maintain bone and muscle mass. We need it to thrive, yet excessively high levels of IGF-1 may increase growth of unwanted tissues like tumors and hasten the aging process.

That said, there’s no indication that IGF-1 increases the formation of tumors. As in Campbell’s rats, it’s likely that IGF-1 makes the organism more robust, but once cancer is present, hastens its growth. And the proposed link between elevated IGF-1 and mortality in humans hasn’t been confirmed. It looks like both high and low levels are bad.

High protein diets reduce longevity.

A study from 2014 had a somewhat paradoxical finding: higher protein intakes had a negative effect on mortality in 50-year-olds, a neutral effect in 65-year-olds, and a beneficial effect in those over 80. Let’s assume for a second that the links are causal—that higher protein intakes are the proximate causes of the shifting mortality risks.

When older people eat more protein, even (or especially) if it comes from evil red meat, they get stronger, build more muscle, improve their ability to take care of themselves, and even think better. The studies didn’t track mortality, but loss of muscle, strength, independence, and cognitive function typically precede death in senior citizens. If higher protein intakes can improve those parameters, they should also improve survival in the population.

Another wrinkle is that dietary protein—especially of animal origin—is the best source of cysteine, a crucial backbone we use to produce the endogenous antioxidant glutathione. A group of researchers recently proposed that a reduction in glutathione synthesis “underlies” the increased mortality linked to low protein intakes in the elderly. Glutathione protects our liver, helps metabolize toxins, and regulates oxidative stress; glutathione deficiency in older populations has been linked to neurodegeneration, heart attacks, and “accelerated aging.”

What’s the verdict?

I’d advise against a low-protein diet unless you have an express reason to do so. You’ll likely grow lethargic, lose muscle mass, gain fat mass, and be less resilient in the face of stressors and illnesses. Maybe it’ll buy you an extra year or two, but at what cost? Low-protein diets have been shown to:

Meanwhile, high-protein diets confer a few potential risks, which I’ve laid out above.

There are clear benefits to higher protein intakes (lean mass retention, muscle growth, fat loss, increased satiety) and legitimate concerns (reduced longevity, excess IGF-1, too much growth of unwanted tissues). How do we square all the evidence? How do we balance the effects?

Short term is fine: Brief bursts of very high protein diets while lifting heavy things can probably help you shed excess weight and retain lean mass. Recent studies find evidence of improved body composition and no evidence of any deleterious effects up to 4.4 g/kg for several weeks at a time. I’m not sure I’d continue eating that much protein for the rest of your life though.

Go high and low: Eat high protein one day, lower protein the next. If you’re trying to gain muscle, you probably need more protein on workout days. If you’re just maintaining, you can get away with far less.

Fast: When someone constantly eats, never going more than 5-6 hours between meals, that person never gives his/her body time to recover and prune damaged cells. Intermittent fasting imposes periods of zero protein and zero food, giving your body a dose of autophagy and a respite from mTOR/IGF-1 activation, and likely making higher protein intakes on feeding days safer.

Overall, I’d say using 100 grams per day as a baseline and going as low as you can without suffering the negative symptoms is worth exploring. It’s likely enough for the majority of people reading this, and if you cycle your protein or fast, you give yourself a chance at some nice autophagy and healthy growth. Plus, you can always increase your intake if you notice negative symptoms.

Athletes aiming for muscle growth and endurance athletes trying to avoid muscle loss may go up to 1.8 g/kg. Dieting athletes should probably go at least that high to preserve lean mass.

Be sure to check out past posts on conditions that determine if you need more or less protein.

Don’t forget my previous protein intake recommendations for different populations.

Now I’d love to hear from you.

How much protein do you eat each day? How do lower—or higher—intakes affect you?

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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42 thoughts on “Should You Eat Less Protein?”

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  1. If you order the free snack bars from Thrive, watch for small print. I just had $59.95 taken from my checking account because I did not read the fine print about a 30 day trial membership. Fortunately, a helpful Thrive representative put the money back into my account. But I DO NOT appreciate this marketing technique.

    1. I ordered the bars and read the information clearly provided on the page then cancelled my temporary membership before the charge. This is not a marketing technique, the information was clearly stated in front of you and by your own admission you chose to ignore it. Stop blaming others for your own ignorance and just appreciate the fact that customer service at Thrive is top notch.

      1. Come now. It’s clearly a “technique”. They do it in hopes that people will be too busy or lazy to read all the details. The only thing they gain from it is the fraction of people they can get because of this. Not wrong in a technical, legal sense, but shady in my book.

      2. I ordered the bars too, and saw the blurb about the free trial membership and the fee that would be taken if not canceled. I wrote down the date it would expire, and went to cancel about a week and a half before the date. They don’t make it very easy for you to find where to cancel, and I had to jump through hoops it seemed to get it done. I was not impressed, and when the customer service person offered a half price membership to try to keep my business, I still declined. I don’t care to deal with a company like that.

    2. I had the same thing happen but was not successful in getting a refund.

  2. Interesting article, but how much (or little) protein I should eat is definitely not on my list of things to be worried about. I get a sufficient amount at almost every meal. I’ve found that I quickly lose interest in eating protein when my body has had enough, so that has become my rule of thumb. It varies. Some days I can enjoy an entire steak; other days anything more than 5 or 6 ounces is a turnoff. Being a member of the clean plate club is a bad idea. People tend to eat too much that way. Any meat left on my plate is given to the family dog.

  3. I think Ron Rosedale has some great info. and ideas, but I disagree with him on his low protein approach, something like no more than 56 grams of protein a day. I’m 5’9″ and 155 lbs, male, 60 years old. After 6 years being Primal I’ve settled in at 90-100 grams a day 5 days a week, which seems to be in my wheelhouse. Two intermittent fasting days a week, two intense bodyweight workouts and 1 sprint session. If I go below 60 grams a day (unless I’m fasting) I get more hungry, and I feel kinda blah. I’m stuffed and lethargic if I get more than 120 grams.

    I worried too about any excess protein turning into glucose. Thanks for the clarification.

  4. Mark, my firsthand experience through trial and error tells me I was consuming too much protein at one point. I was up around 130-140 grams on certain days. I have since cut back and aim to consume 25-30 grams within a meal now. It has made a positive impact on my recent efforts to lean out a little bit.

    Based on your article, though, I might stand to benefit from not cutting back as much as I have. I’ll try cycling certain days for higher protein like you suggest, especially on my kettle bell workout days.

    Thanks for the helpful info.

  5. Thrive market took $59.95 from my checking account because I did not read the fine print about membership when I got my free snack bars. While it was my error, I don’t like this marketing technique.
    They are going to return the money to my account.

    1. Okay, the mistake was your fault and Thrive is going to rectify it by returning your money…so what’s your point? If you don’t like that kind of marketing, then don’t buy from them.

  6. Is the forum down for anyone else? I’ve tried two computers on two different networks and I keep getting a database error. Unsure of who to contact here…

    1. I’ve had the same problem-it worked for awhile yesterday but is down again this morning.

  7. My mom has Parkinson’s disease along with type 2 diabetes and has been advised “not to eat too much protein” because of her Parkinson’s. Mom’s muscles are practically nonexistent, which does not help her in getting around, to say the least. Do you think this advice about protein is overblown?

  8. This is precisely why fat needs to be most peoples number one macronutrient. Some highly active people might get away with eating a higher carb diet. By higher I mean in the 175-250 grams a day category. I don’t think anyone (even the extremely active) could get away with the 350-450 grams of carbs a day the USDA recommends. I eat about 110-115 grams of protein a day, for my weight (201 lbs.) I feel that’s about right. Rest of my calories are from fat and paleo approved carb sources, exception with raw dairy.

    1. I agree and 65%-70% of what I eat comes from fats, except on special occasion and strenuous workout where I may up my protein to around 90/100 grams, which might seem a lot consider I am 5’8″ and 146 lbs

  9. I think the problem is when people start eating a bunch of processed protein bars and shakes made with soy or whey protein. These are not necessarily used by the body the same way protein from a steak or chicken would be.

  10. I eat a gram per pound or 145 grams per day. I also walk 25 miles per week, lift twice a week and sprint at least once per week. It seems to suit me as I sleep well and have 8% body fat. I experimented with eating about 100gm for awhile but occasionally had poor sleep and resulting carb cravings.

  11. Weird. Turns out I’ve been heeding the recommendations by accident. On the days where I work out hard (sprints, lifting HIIT) I can eat a couple pounds of various meats and organs, with a slightly higher intake the following day too. Most other days, I get enough through sardines, oysters, and eggs for maintenance. I tend to feel much better if I’m not cramming tons of protein through the system every day.

  12. It’s interesting to see how protein intake can have a positive and negative impact based on so many factors. I am, as I assume many readers on this site are, a big fan of protein as a nutrient source. And I absolutely agree people consume the incorrect amounts (way too high or low). The 100 grams of protein/day is a good rule of thumb for starters. And I might experiment with the 4.4g/kg body weight for a little too. Great read.

  13. Spend time on pubmed looking at protein type, amount, amino acid balance, etc, and you’ll find a wide variety of results. Because protein/meat is still “politically incorrect,” headlines will be mostly anti-protein. There was one study in mice or rats (I forget) where they had quite high protein amounts but were calorically restricted. Not only did they have good looking markers for aging, but they also had good body composition and grip strength.

  14. Excellent article!

    The safest way not to overdose on protein is by staying clear of lean cuts; in other words, stick to fatty cuts. And If you google “Empirica: eat meat”, you will come across a web site that evolves around eating meat and drinking water only, without ill effect or lack of nutrients. And since no other food is taken, they claim that it’s less costly then a Primal or Paleo, but stress, that the meat should be from grass fed only. Somehow and as much as I like meat, I can’t see myself eating 4/5 LBS of meat a day. Nor do I think that it’s any cheaper

    1. I nearly forgot. Since N-A-C (N-ACETYL CYSTEINE) s a by-product of glutathione and both are important for dealing with Reactive Oxygen Species and Oxidative Stress, wouldn’t it be a good idea to supplement with? In particular, to those with high Ferritin values and thyroid issues? After all, Iron overload comes at a price

      1. My understanding is that NAC is a building block of glutathione. As an aside, acetaminophen (paracetamol) reduces glutathione levels and is the mechanism for liver damage. I take NAC occasionally to boost glutathione.

        1. Thank you. I’ve mentioned it, is due to the fact that excess iron which I suffer from (around 400), may effect many organs and joints and from what I read also lower glutathione, so I am going to try it after consulting with my Hematologist.

          Now, what was so offensive about my comment to earn me a minus? 🙂

          1. Oh my! I didn’t give you a minus! I wonder if I accidently touched that on the screen when hitting reply?

          2. If that was the case,I was able to undo it by giving a up vote.

          3. Haha before u wonder.. for some reason the website turned my iPhone smiley emoji into question mark

  15. Not going to eat insects folks (on purpose) … just not gonna do it. 🙂

  16. There is more to this particular conversation than purely protein intake level. I am currently writing my PhD dissertation on this very topic. The source and processing of the protein actually matters a great deal. Animal proteins that are unprocessed and properly prepared (ie slow cooked and not overcooked) are highly digestible and easily absorbed so that having excess protein enter the colon to promote carcinogenesis is unlikely. On the other hand, eating incomplete proteins that are hard to digest cause imbalances in amino acids in the body and also are more likely to survive undigested to the colon for fermentation (ie highly processed plant proteins and even highly processed milk proteins). Therefore, my biggest concern in this area is consumption of plant-based proteins as the primary protein source and highly processed proteins, such as those found in processed foods and protein powders. If you are eating paleo-primal style it is unlikely that you will eat sufficient amounts of damaged protein to cause problems. Keep in mind that these studies are often done on animals that are fed highly processed diets and most people who are in research studies are also consuming highly processed foods. Researchers fail to comment on the source and processing of the proteins and what affect this might have.

    1. This is such a critical point Megan. Thanks for bringing it up.

      When reading a study that’s contradictory to common sense the first questions I ask are “What is the source of the nutrient being studied? Is it present in its whole form? How has it been processed and prepared?” Of course there are other variables too numerous to mention that we need to be aware of as well.

      I’m curious, what is the impact of soaking/sprouting of the incomplete proteins? While I eat a very low grains (I’m celiac), partially primal diet, I simply don’t enjoy large amounts of meat and include soaked legumes/lentils in my diet. And probably too many nuts and seeds (soaked and dehydrated).

      If your dissertation is complete please share the conclusion.

  17. I guess I’ve been cycling protein without realizing it. While I have no idea how many grams I consume, I know that my protein intake varies from day to day. Not on purpose, it’s just a matter of listening to my body. Some days I have a generous portion of animal protein at each meal, plus collagen in my am coffee. Other days I’m just not feeling it. I always have plenty of fat, but even that varies from day to day.

  18. Protein is & always has been the only thing that satisfies by ridiculous, completely out-of-hand appetite. I suffer from ferocious hunger, all the time, since adolescence. I’d have to keep a food log but I think I likely go well over 100g a day.

    My lifestyle of exercise & diet (loosely primal) is the thing keeping me from being morbidly obese. Yes, I eat a lot of healthy fats with all that protein. I’ve no idea if I have astrocyte swelling. I googled it but I am still mystified. I feel great & in better shape than I’ve ever been. But after reading this article, I am unsure if I am eating too much protein or not.

  19. At last, SI in a blog post.

    Living outside the US, I can’t be the only one that rolls there eyes at grms/lb, ºF or other imperial measurements… or Donald Trump, for that matter.

  20. I truly do not believe there is one size fits all. Sure studies have been done that have drawn some conclusions, but again, we may all be human, but we are all still built differently. I myself need to eat a very high (animal) protein diet, as that is the only way I can survive. My digestive system works very well with animal protein (and fat) but cannot process roughage/fiber/carbs… So giving the advice of eating X amount per kg of body weight is very generic in my personal opinion.

  21. Thank you for your blog post. Can we really trust the results of the studies you link to ? I can find, with easy google searches, studies showing results that contradict these conclusions. I know that I should find them and link to them now (or perhaps that is what would be expected) but I am purposefully not going to do that, because it just pushes us deeper down the rabbit hole. Hands down, without a doubt, there are professional researchers out there that believe high meat protein diets reduce longevity. And there are professional researchers, and certainly bloggers, that believe the opposite. What is the layperson to do? In the past I would have been inclined to say that the way you look and feel should be a good guide in terms of how to eat, but I’m not so sure about that. We have access to a lot more food that we used to, and the impulse to cram in high calorie food whenever we can is basically built into our DNA. Also, I am a healthy person that feels good and energetic no matter what I eat – lucky, yes, but I’d like to stay healthy into my golden years, and I am setting the stage for those years right now, so I’d like to do it right. There is also the issue of what we believe about the food we are eating and how that can alter its effects on our bodies. The only way I know to solve this huge conundrum is to look to the populations of the world that live the longest and the best, and emulate their diet and lifestyle best I can. That is literally the only thing that makes sense for me to do.

  22. Should someone with Stage 3A chronic kidney disease limit animal protein or total protein? What I’ve read is that 0.8 grams per kilogram body weight, or up to 15% of calories is recommended. Is that correct?

  23. I’m 6ft 175. Is 100grms of protein a day a good baseline to start? Or should I do a body fat test and figure out the exact amount based on .7 grams per lean body mass. I feel good and am happy with how I look so I haven’t done one of those tests and have no idea where I am in terms of body fat %