Written by: Viktor Forsmann, bachelor in Nutrition and Health
Protein has become a bit of a "buzzword", where you can hardly find a food that has not been made a "protein edition" of the original food (yes, I think of Snickers and Mars). In this article, I will briefly review what protein is, whether there is any difference between whether protein comes from animal or plant sources, when the protein requirement is increased - and whether protein is harmful to your kidneys or your liver.
What is protein?
Protein is one of the macronutrients that helps our machinery to function normally. Protein consists of chains of amino acids linked together in long polypeptide chains that together form a protein (1). There are both essential and non-essential amino acids (1,2). The amino acids are essential because we can not produce them ourselves and thus have a need to get them through the diet (1). In general, it suggests that non-essential amino acids are not necessary to stimulate our protein synthesis (2), so it may make sense to focus on quality protein (ie protein with a high amount and wide range of essential amino acids).
Protein quality - does it matter?
Protein quality has been a common argument that many bodybuilders / elite exercisers have not wanted to switch to a plant-based diet. Previous research also suggests that protein quality is lower in plant-based foods compared to animal foods (3,4,5). However, a brand new study from 2021 found no difference among vegans and meat eaters when both groups ate 1.6g / kg / day protein in relation to building muscle mass (6). In a major literature review from 2021, the authors also conclude that there is a need for more long-term studies, where one checks for more potential confounders (~ causal confusion) (5). In general, it is recommended to have some variation in one's protein sources such as vegan or increase protein intake (7) - however, one is unsure,
When does one's need for protein increase?
One's protein requirement increases as the amount of exercise increases (8). The protein requirement in connection with strength training seems to be between 1.6-2.2 g per. kg body weight per day (8). Previously, people were of the belief that endurance training did not have such a high protein requirement (9), but this has been well and thoroughly doubted (10,11). In one study a protein requirement of (~ 1.65 g / kg / day) was found (10), whereas in another study a protein requirement of 2.1-2.6 g / kg / day was found (11). The difference between the protein requirements is probably attributed to a smaller carbohydrate intake among the participants in one study (11). So it suggests that your protein intake is increased relatively much no matter what type of exercise you are doing.
According to the World Health Organization, there is no scientific basis for linking a high-protein diet with kidney disease among ordinary people.
Is protein harmful to the kidneys when you are healthy and well?
Good old classic. Primarily; no. Protein is not harmful to your kidneys if you are healthy (12,13,14). According to the World Health Organization, there is no scientific basis for linking a protein-rich diet with kidney disease among ordinary people (12). In relation to exercisers, a team of researchers has studied the effects of an extremely high protein intake (3.4-4.4 g / kg / day) in 8 weeks. Here, the researchers found no changes in the participants' kidney or liver function (13,14). The same team of researchers has also studied the effects of a high protein intake (3 g / kg / day) for 16 weeks and has also not found any negative effects on kidney or liver function (15). And so we are talking about extremely high protein intakes here.
I hope this article has helped to nuance your understanding of protein quality, protein needs and protein intake in relation to your health. There are now a lot of myths (especially that the protein requirement should be less in endurance training) in relation to protein. I hope this article has helped puncture some of these myths. Happy protein!
(1) Berg, JM, Tymoczko, JL, Stryer, L., & Stryer, L. (2015). Biochemistry. New York: WH Freeman.
(2) Wolfe RR. Branched-chain amino acids and muscle protein synthesis in humans: myth or reality ?. J Int Soc Sports Nutr. 2017; 14:30. Published 2017 Aug 22.
(3) Yang Y, Churchward-Venne TA, Burd NA, Breen L, Tarnopolsky MA, Phillips SM. Myofibrillar protein synthesis following ingestion of soy protein isolate at rest and after resistance exercise in elderly men. Nutr Metab (London). 2012 Jun 14; 9 (1): 57. doi: 10.1186 / 1743-7075-9-57. PMID: 22698458; PMCID: PMC3478988.
(4) Putra C, Konow N, Gage M, York CG, Mangano KM. Protein Source and Muscle Health in Older Adults: A Literature Review. Nutrients. 2021 Feb 26; 13 (3): 743. doi: 10.3390 / nu13030743. PMID: 33652669; PMCID: PMC7996767.
(5) of Vliet S, Burd NA, of Loon LJ. The Skeletal Muscle Anabolic Response to Plant- versus Animal-Based Protein Consumption. J Nutr. 2015 Sep; 145 (9): 1981-91. doi: 10.3945 / jn.114.204305. Epub 2015 Jul 29. PMID: 26224750.
(6) Hevia-Larraín, V., Gualano, B., Longobardi, I. et al. High-Protein Plant-Based Diet Versus a Protein-Matched Omnivorous Diet to Support Resistance Training Adaptations: A Comparison Between Habitual Vegans and Omnivores. Sports Med 51, 1317–1330 (2021). https://doi.org/10.1007/s40279-021-01434-9
(7) Rogerson D. Vegan diets: practical advice for athletes and exercisers. J Int Soc Sports Nutr. 2017; 14:36. Published 2017 Sep 13. doi: 10.1186 / s12970-017-0192-9
(8) Moore DR. Maximizing Post-Exercise Anabolism: The Case for Relative Protein Intakes. Front Nutr. 2019 Sep 10; 6: 147. doi: 10.3389 / fnut.2019.00147. PMID: 31552263; PMCID: PMC6746967.
(9) Jäger, R., Kerksick, CM, Campbell, BI, Cribb, PJ, Wells, SD, Skwiat, TM, et al. (2017). International society of sports nutrition position position stand: protein and exercise. J. Int. Soc. Sports Nutr. 14:20. doi: 10.1186 / s12970-017-0177-8
(10) Kato H, Suzuki K, Bannai M, Moore DR. Protein requirements are elevated in endurance athletes after exercise as determined by the indicator amino acid oxidation method. PLoS One 11: e0157406, 2016. doi: 10. 1371 / journal.pone.0157406.
(11) Bandegan A, Courtney-Martin G, Rafii M, Pencharz PB, Lemon PWR. Indicator amino acid oxidation protein requirement estimate in endurance-trained men 24 h postexercise exceeds both the EAR and current athlete guidelines. Am J Physiol Endocrinol Metab. 2019; 316 (5): E741–8.
(12) World Health Organization, Technical report series 935. Protein and amino acid requirements in human nutrition: report of a joint fao / who / uni expert consultation. 2011.
(13) Antonio J, Ellerbroek A, Silver T, Orris S, Scheiner M, Gonzalez A, et al. A high protein diet (3.4 g / 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; 12:39
(14) Antonio J, Peacock CA, Ellerbroek A, Fromhoff B, Silver T. The effects of consuming a high protein diet (4.4 g / kg / d) on body composition in resistance-trained individuals. J Int Soc Sports Nutr. 2014; 11:19
(15) Antonio J, Ellerbroek A, Silver T, Vargas L, Peacock C. The effects of a high protein diet on indices of health and body composition – a crossover trial in resistance-trained men. J Int Soc Sports Nutr. 2016; 13: 3