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If you’re an athlete like me, one of the primary pieces of advice you are given is to eat a high protein diet. This is a great piece of advice for any athlete to follow. The science on the benefits of eating a higher protein dieting is quite unequivocal. Despite the substantial variability across individuals regarding nutritional requirements, a higher protein intake is important in any diet that can claim the title of being “healthy.” Protein and its constituent molecules, amino acids, are characteristically known as the body's building blocks. This is because it is responsible for building tissues, including muscle, skin, organs, and tendons. Likewise, it is integral to the processes of creating several hormones, enzymes, and brain chemicals. Some of the other important roles that protein plays in the body also include the transportation of important molecules, acting as antibodies, being a source of energy (as it yields calories), and helping maintain the acid-base balance of the body by acting as a buffer.

Thus, having protein in your diet is an integral part of the recovery process, as was alluded to in my interview with Dr. Layne Norton. This has been vindicated through a few studies. One such study from 2017 in The American Journal of Clinical Nutrition (1) studied post-op patients receiving ERAS care. It showed that patients who consumed a higher protein diet versus patients who did not have shorter and fewer instances of infectious complications. Likewise, the same study showed (2) that patients who consumed a higher protein intake had a higher rate of being discharged from the hospital earlier than their lower protein counterparts.

However, like most nutritional advice, you are not told why this is the right thing to do. Given that you are not told why this is the right thing to do, you begin to hear about the potential downsides to eating a higher protein diet. Rumors and misinformation spread easily when we are not adequately informed, to begin with. Because we are not told why protein is important, these myths slide by and become almost credos. This is to the point where such myths are featured in nutritional science textbooks and documentaries!

Here are the top 3 myths that are most often spread about the high-protein diet:

1. “You have to eat excessive amounts of protein if you’re going to succeed as an athlete.”

Walking into most gyms, you will find that the back counter fridges and the smoothie bars are stacked with whey protein powder or pre-mixed protein shakes. This is all well and good. Whey protein is one of the highest quality sources of protein due to its high concentration of the amino acid leucine, which is essential to muscle protein synthesis. It is a nutritional consensus that protein is integral to muscle growth, fat loss, athletic performance, and overall health (3). However, if you walk up to anyone in the gym, it is quite likely that they will tell you that you have to eat a lot of protein to attain those goals. What a lot usually means is, well, a lot.

For example, when I first started lifting weights, I was told that I should eat 2 grams of protein per lb of body weight. At the time, I weighed about 140 lbs. In turn, I was eating about 280 grams of protein a day! To speak from experience, it was a lot of chicken and a lot of gastrointestinal distress! Was this necessary or beneficial?

The short answer is absolutely not. Even as an active individual, this was way too much. According to a study published by The Journal of The International Society of Sports Nutrition, conducted at Nova Southeastern University in 2014, while a very high protein diet proved to have no side effects, it provided no additional performance or body beyond a certain point composition benefits (4). This study displayed that a 4.4 gram per kilogram bodyweight consumption — which according to the study’s ending discussion, was the highest intake ever studied — of protein per day was safe but was essentially useless. This begs a further question: what protein intake is sufficient for athletes?

It is a lot less than the recommendation of 2 grams per lb of bodyweight. According to Dr. Eric Helms, when an athlete is looking to optimize protein benefits, they should consume about 0.8 grams of protein per pound of body weight (5). There are very few occurrences in the literature where anything higher than this intake has proven to be more beneficial to performance or body composition. The RDA (recommended daily allowance) of protein for adults is 0.8 grams of protein per lb of bodyweight. However, it is becoming more clear that this recommendation is actually lower than optimal for normal healthy adults. According to Donald Layman from the nutrition department at the University of Illinois, the protein RDA is too low, as “diets with increased protein have now been shown to improve adult health with benefits for treatment or prevention of obesity, osteoporosis, type 2 diabetes, metabolic syndrome, heart disease, and sarcopenia”(6). Dr. Laymen recommends eating at least 30 grams of protein for normal healthy adults with every meal to maintain healthy muscles and bones. (7)

The only exception to this recommendation is when you are dieting to lose weight. While there is not enough data to prove that a higher protein intake than 0.8 grams per pound of body weight during a period of caloric restriction will retain a higher amount of lean body mass, what it will do is increase the satiety of the diet and potentially provide better psychological energy levels (8). A more satiating diet while restricting calories makes adhering to a diet much easier (9). Thus, don’t be afraid of protein but don’t overdo it. It’ll save you time, money, and gastrointestinal distress.

2. “High Protein Diets are Bad For Your Kidneys.”

One of the unique aspects of protein is that of the three macronutrients (carbohydrates, fats, and protein), it is the only one that contains nitrogen. Hence, it has been speculated that the higher nitrogen consumption intrinsic to a higher protein diet will put a higher amount of strain on your kidneys to process the additional nitrogen, which can lead to kidney damage or even failure. Likewise, this theory has been asserted in corollary that patients who have suffered renal failure are strongly advised to eat a low protein diet.

This theory has some truth to it. However, the conclusion that it draws — namely, that high protein diets are generally dangerous for the kidneys — is fallacious. Understanding protein metabolism and its relation to the kidneys is important to understand why a high protein diet is not harmful to the kidneys under most circumstances. Ammonia is produced in the body when amino acids (the constituent molecules of protein) are deaminated in the liver. Deamination is, plainly speaking, the process of stripping nitrogen from amino acids. When the liver has released ammonia (NH3), it is converted to urea due to its exposure to carbon dioxide (CO2). Through the bloodstream, urea is sent to the kidneys, and the kidneys dispose of urea. This is how the body disposes of excess nitrogen. (10) That is, the kidneys — insofar as they’re healthy — are meant to be dealing with a higher nitrogen intake. This is called a positive nitrogen balance, where the body synthesizes more protein than it degrades and where nitrogen intake exceeds excretion. This is a state that is crucial to the body in periods of natural growth, recovery, or illness. A negative protein balance is when the body degrades more protein than it synthesizes and where nitrogen intake is less than excretion. This is a symptom of starving people, people with protein deficiencies, and people who are suffering from severe physical injuries such as burns. (11)

So yes, a higher intake of protein will potentially cause the kidneys to work harder because it is their job to excrete the byproducts of protein. If you are consuming a higher amount of protein, the kidneys will have more urea to excrete. However, this is not harmful to the kidneys and certainly does not lead to kidney disease. There is no evidence that healthy kidneys will become unhealthy due to eating more protein—a higher excretion rate of urea doesn’t equate to a higher blood concentration of urea. A study published in the International Journal Of Sports Nutrition in 2000 comparing bodybuilders with high protein intakes (2.8g per kg of body weight) versus well-trained athletes eating a moderate protein intake showed no significant difference in kidney function between the groups (12). Likewise, in a study published by the Journal of Nutrition and Medicine in 2016, a high protein diet was shown to have no harmful effects in healthy individuals (13). Moreover, a systematic analysis of the data on the connection between protein and renal function published by the International Society of Sports Nutrition concluded that “it is clear that protein restriction does not prevent the decline in renal function with age, and, in fact, is the major cause of that decline. A better way to prevent the decline would be to increase protein intake. there is no reason to restrict protein intake in healthy individuals to protect the kidney.” (14) In other words, a low protein diet is only not beneficial towards preventing renal failure. It is quite the contrary. Given that the two primary causes of kidney damage are hypertension and diabetes, it is the case that a higher protein diet can help improve the state of both of these conditions for the better by lowering blood pressure and improving blood glucose control (15,16).

Where things change, however, is if an individual already has some renal dysfunction. People who have already existing kidney damage might further that damage if they consume a higher protein diet. A meta-analysis published in 2004 in the journal of the International Society of Sports Nutrition showed that individuals who have pre-existing kidney dysfunction are advised to consume a lower protein diet, but that no research has carried out the notion, plausibly, that a high protein diet will cause kidney dysfunction (17).

Hence, the conclusion we should draw from this myth is as follows: if you have healthy kidneys, eating a higher protein diet is most likely perfectly safe, but if you have kidney damage, you should probably restrict your protein intake.

3. “High Protein Diets are Bad For Your Bones.”

It has been theorized in recent years that a high protein diet might cause osteoporosis. As a student in nutrition, this myth has gotten to the point of being written in highly reputable nutritional science textbooks. The rationale behind this belief is that eating too much protein causes calcium excretion because a higher protein intake might cause an increase in the acid load of the body.

This is a claim that the data does not bear out. For instance, a study published in The Journal of Clinical Endocrinology & Metabolism in 2004 showed that an increase in dietary protein not only does not at all increase bone calcium excretion, it also showed that an increase in protein intake might improve bone health in the elderly (18). Likewise, it has been shown in various epidemiological studies — one of which was published by Osteoporosis International in 1993 — that a higher protein intake is associated with a higher level of bone mineral density, which is antithetical to what precedes osteoporosis (19,20). It can also be deduced that many of the highest quality sources of protein, such as dairy, are also some of the best sources of calcium, which begs the question of how this would cause calcium excretion. These protein sources have high calcium levels, but they also contain vitamin D, which makes calcium more bioavailable (which means that it is more readily absorbed and utilized by the body).

To quote from Dr. Layne Norton, “Thus, while increasing protein may increase calcium excretion, there is no evidence that the increased calcium is lost in urine is from bone, and the overall net calcium balance is either unaffected or actually improved by a high protein diet.” (21) To further this point, it seems quite unequivocal based on the research to assert that a higher protein diet is actually beneficial for your bones. For instance, a study published in The Journal of Clinical Endocrinology & Metabolism in 2004, showed that not only did a higher protein diet not excrete calcium, it also increased the production of bone health-promoting hormones like IGF-1 (22). Furthermore, according to a 2017 review of a meta-analysis by The American Journal Of Clinical Nutrition (23), there is no evidence that a higher protein intake has adverse effects on bone health, but the evidence — which needs to be further expanded upon — currently points in the direction of showing that a higher protein diet has a positive effect on bone health.

As an honorable mention, it has been claimed that eating a high protein diet protein might lead to cancer. For instance, in the documentary What The Health, it was postulated that eating eggs, dairy, and meat is as bad for you as smoking cigarettes. These claims are based on a study recently published in Cell Metabolism in 2014 titled “Low Protein Intake Is Associated with a Major Reduction in IGF-1, Cancer and Overall Mortality in the 65 and younger but Not Older People” (24). This study was epidemiological and used rodents primarily. However, the problem with epidemiological studies is that they extrapolate their connections after the fact, meaning they cannot make causal claims. Epidemiological data is purely for the sake of sparking further research. Right off the bat, then, it is intellectually disingenuous to say that protein causes cancer. Likewise, this study is flawed in many important respects. Firstly, this study had no participants under the age of 50, which given its title, is dishonest. Likewise, it did not actually find any correlation between a higher protein diet and all-cause mortality, which its title suggests it did. Furthermore, “no plausible relation was found between higher protein intake with all-cause mortality, cancer-related mortality, or cardiovascular mortality overall. A small increase in risk was seen when looking only at people between the ages of 50–65”, as Kamal Patel of examine.com (25) said. Patel states further, “A more accurate headline for this study would have been ‘High protein for those between 50 years to 65 years old who have poor diet and lifestyle habits may be associated with increased cancer risk.’”Also, the rodent portion of the study was not replicated by the human portion of the study, where the humans who were studied did not have tumors, whereas the rodents who were studied were implanted with tumors (25). Extrapolating that protein causes cancer from such methodological flaws should be taken with a huge grain of salt. This grain of salt should be taken within the landscape because, according to The American Journal of Clinical Nutrition, almost all food ingredients have been associated with cancer at some point or another in the history of nutritional science (26).

Citations:

(1) Yeung SE, Hilkewich L, Gillis C, Heine JA, Fenton TR. “Protein intakes are associated with reduced length of stay: a comparison between Enhanced Recovery After Surgery (ERAS) and conventional care after elective colorectal surgery.” The American Journal of Clinical Nutrition, 2017, Results.

(2) Yeung SE, Hilkewich L, Gillis C, Heine JA, Fenton TR. “Protein intakes are associated with reduced length of stay: a comparison between Enhanced Recovery After Surgery (ERAS) and conventional care after elective colorectal surgery.” The American Journal of Clinical Nutrition, 2017, Results.

(3) John D Bosse, Brian M Dixon. “Dietary protein to maximize resistance training: a review and examination of protein spread and change theories” International Society of Sports Nutrition Journal, 2012, Conclusions.

(4) Jose Antonio, Corey A Peacock, Anya Ellerbroek, Brandon Fromhoff, and Tobin Silver. “The effects of consuming a high protein diet (4.4 g/kg/d) on body composition in resistance-trained individuals” The Journal of The International Society of Sports Nutrition, 2014, Discussion & Conclusion.

(5) Morton, R.W., et al., A systematic review, meta-analysis and meta-regression on the effect of protein supplementation on resistance-training-induced gains in muscle mass and strength in healthy adults. Br J Sports Med, 2018. 52(6).

(6) Paddon-Jones D, Westman E, Mattes RD, Wolfe RR, Astrup A, Westerterp-Plantenga M. Protein, weight management, and satiety. Am J Clin Nutr. 2008;87:1558S–1561S. [PubMed] [Google Scholar] Paddon-Jones D, Short KR, Campbell WW, Volpi E, Wolfe RR. Role of dietary protein in the sarcopenia of aging. Am J Clin Nutr. 2008;87:1562S–1566S. [PubMed] [Google Scholar] Heaney RP, Layman DK. Amount and type of protein influence bone health. Am J Clin Nutr. 2008;87:1567S–1570S. [PubMed] [Google Scholar] Layman DK, Clifton P, Gannon MC, Krauss RM, Nuttall FQ. Protein in optimal health: heart disease and type 2 diabetes. Am J Clin Nutr. 2008;87:1571S–1575S. [PubMed] [Google Scholar]

(7) Donald K. Laymen. “Dietary Guidelines should reflect new understandings about adult protein needs.” Nutrition & Metabolism, 2009, New understandings about protein for Dietary Guidelines.

(8) Antonio, J., et al., A high protein diet (3.4/kg.d) combined with a heavy resistance training program improves body composition in healthy trained men and women — a follow-up investigation. J Int Soc Sports Nutr, 2015. 12.

(9) Antonio, J., et al., The effects of consuming a high protein diet (4.4g/kg/d) on body composition in resistance-trained individuals. J Int Soc Sports Nutr, 2014. 11.

(10) Whitney, Rolfes. “Understanding Nutrition: Fifteenth Edition.” Cengage, 2019, Chapter 6: Protein.

(11) Whitney, Rolfes. “Understanding Nutrition: Fifteenth Edition.” Cengage, 2019, Chapter 6: Protein.

(12) Poortmans JR, Dellalieux O. Do regular high-protein diets have potential health risks on kidney function in athletes? Int J Sports Nutr 2000;10:28–38.

(13) Antonio, Jose et al. “A High Protein Diet Has No Harmful Effects: A One-Year Crossover Study in Resistance-Trained Males.” Journal of nutrition and metabolism vol. 2016 (2016): 9104792. doi:10.1155/2016/9104792

(14) Manninen, Anssi H. “High-Protein Weight Loss Diets and Purported Adverse Effects: Where is the Evidence?.” Journal of the International Society of Sports Nutrition vol. 1,1 45–51. 10 May. 2004, doi:10.1186/1550–2783–1–1–45

(15) Antonio, Jose et al. “A High Protein Diet Has No Harmful Effects: A One-Year Crossover Study in Resistance-Trained Males.” Journal of nutrition and metabolism vol. 2016 (2016): 9104792. doi:10.1155/2016/9104792

(16) Levey AS1, Adler S, Caggiula AW, England BK, Greene T, Hunsicker LG, Kusek JW, Rogers NL, Teschan PE. “Effects of dietary protein restriction on the progression of advanced renal disease in the Modification of Diet in Renal Disease Study.” Journal of The American Society of Nephrology, 1996.

(17) Manninen, Anssi H. “High-Protein Weight Loss Diets and Purported Adverse Effects: Where is the Evidence?.” Journal of the International Society of Sports Nutrition vol. 1,1 45–51. 10 May. 2004, doi:10.1186/1550–2783–1–1–45

(18) Bess Dawson-Hughes Susan S. Harris Helen Rasmussen Lingyi Song Gerard E. Dallal The Journal of Clinical Endocrinology & Metabolism, Volume 89, Issue 3, 1 March 2004, Pages 1169–1173, https://doi.org/10.1210/jc.2003-031466

(19) Geinoz G, Rapin CH, Rizzoli R et al. Relationship between bone mineral density and dietary intakes in the elderly. Osteoporos Int 1993;3:242–8.

(20) Cooper C, Atkinson EJ, Hensrud DD et al. Dietary protein intake and bone mass in women. Calcif Tissue Int 1996;58:320–325.

(21) Biolayne. Are High Protein Diets Safe?, 2016, https://www.biolayne.com/articles/nutrition/high-protein-diets-safe/ Accessed on 27 May 2019.

(22) Bess Dawson-Hughes Susan S. Harris Helen Rasmussen Lingyi Song Gerard E. DallalThe Journal of Clinical Endocrinology & Metabolism, Volume 89, Issue 3, 1 March 2004, Pages 1169–1173, https://doi.org/10.1210/jc.2003-031466

(23) Marissa M Shams-White Mei Chung Mengxi Du Zhuxuan Fu Karl L InsognaMicaela C Karlsen Meryl S LeBoff Sue A Shapses Joachim Sackey Taylor C Wallace The American Journal of Clinical Nutrition, Volume 105, Issue 6, June 2017, Pages 1528–1543, https://doi.org/10.3945/ajcn.116.145110

(24) Morgan E. Levine, Jorge A. Suarez, Sebastian Brandhorst, Priya Balasubramanian, Chia-Wei Cheng, Federica Madia, Luigi Fontana, Mario G. Mirisola, Jaime Guevara-Aguirre, Junxiang Wan, Giuseppe Passarino, Brian K. Kennedy,Min Wei, Pinchas Cohen et al. “Low Protein Intake Is Associated with a Major Reduction in IGF-1, Cancer, and Overall Mortality in the 65 and Younger but Not Older Population.” Cell Metabolism, 2014.

(25) Examine. High Protein Diets Linked To Cancer: Should You Be Concerned?, 2018, https://examine.com/nutrition/high-protein-diets-linked-to-cancer-should-you-be-concerned/

(26) Is everything we eat associated with cancer? A systematic cookbook review Jonathan D Schoenfeld John PA Ioannidis The American Journal of Clinical Nutrition, Volume 97, Issue 1, January 2013, Pages 127–134, https://doi.org/10.3945/ajcn.112.047142