Of all the myths floating around out there this one seems to be the most popular.
I often hear from clients that “too much protein is really bad for your kidneys..”. And I always ask the magic question: “Why?”
How simple is it to question and challenge everything you hear by asking “why?” It is just as Socrates did with his methods whenever he tried to uncover the truth behind every myth.
What is too much protein? Let’s define it as 2-3 more than the amazingly low RDA.
So how did the myth start! A quick research I did revealed that it started from studies on patients with kidney disease. And why was it so? People with kidney disease have difficulty filtrating protein, and that is why in some cases they are on a low-protein diet. So…Just because patients with kidney disease could not filtrate protein, people hastily concluded that too much protein must be hard on the kidneys. What a conclusion, right?!?
So what was the only way to determine if this was true or not? Do our research! Studies conducted on the effect of higher protein intakes have found that higher protein intake is completely safe. In the short-term, the body adapts to the higher protein intakes which change some markers of kidney function. This is part of the adaptation process to the additional protein. However, long-term consumption of higher amounts of protein does not have a negative impact on kidney function1-7
Dr. Jose Antonio and his team on their latest study2 instructed participants to consume ≥3 grams of protein per kg per day (or ≥3g/kg/day). Consuming ≥3 g/kg/day from whole foods is pretty difficult so the participants on the high protein diet were supplementing with whey protein. And as if that wasn’t enough, they went a step further and examined two participants with the highest protein intakes of 4.66 and 6.59 g/kg/day (WOW that’s high!! Imagine the juicy steaks) and found no harmful effects on renal function in either individual. Oh God almighty that’s a lot of protein!! In the conclusion of the research the author states “There were no changes in any of the variables regarding blood lipids and a comprehensive metabolic panel. We examined the two individuals with the highest recorded protein intakes (4.66 and 6.59 g/kg/day) and found no deleterious effects on renal function in either individual”.
And one more study to bust the myth.
We know from existing research that diets high in protein cause hyper filtration and we should expect an initial increase in glomerular filtration! Glomerular what?? Glomerular filtration. GFR – glomerular filtration rate is the best test to measure your level of kidney function and assess how well your kidneys are working. But this study by Juraschek et al. 20135 indicated that protein increased eGFR (so..?) and concluded that “Whether long-term consumption of a high-protein diet leads to kidney disease is uncertain.”
The claim that protein intake leads to kidney failure is not supported by the facts! In Martin et al. 2005 “Dietary protein intake and renal function” the conclusion is that “Although excessive protein intake remains a health concern in individuals with pre-existing renal disease, the literature lacks significant research demonstrating a link between protein intake and the initiation or progression of renal disease in healthy individuals. More importantly, evidence suggests that protein-induced changes in renal function are likely a normal adaptive mechanism well within the functional limits of a healthy kidney. Without question, long-term studies are needed to clarify the scant evidence currently available regarding this relationship. At present, there is not sufficient proof to warrant public health directives aimed at restricting dietary protein intake in healthy adults for the purpose of preserving renal function”
Protein restricted diets are helpful for some cases of people who have CKD (Chronic Kidney Disease). Consuming protein does not cause kidney problems. And what is more, the fat-soluble vitamins and saturated fatty acids found in animal foods are essential for properly functioning kidneys (So how reasonable is that?).
And to sum up!
Thank God for Dr. Jose Antonio and lab published (The day I was submitting my draft!!) their latest and the first ever research which is the first 1-year longitudinal investigation in resistance-trained males that demonstrates the lack of harm caused by a high protein diet.
1. Antonio, J., Ellerbroek, A., Silver, T., Orris, S., Scheiner, M., Gonzalez, A. and Peacock, C. A., 2015. 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. Journal of the International Society of Sports Nutrition, 12 (1).
2. Antonio, J., Ellerbroek, A., Silver, T., Vargas, L. and Peacock, C., 2016. The effects of a high protein diet on indices of health and body composition – a crossover trial in resistance-trained men. Journal of the International Society of Sports Nutrition, 13 (1).
3. Li, Z., Treyzon, L., Chen, S., Yan, E., Thames, G. and Carpenter, C. L., 2010. Protein-enriched meal replacements do not adversely affect liver, kidney or bone density: An outpatient randomized controlled trial. Nutrition Journal, 9 (1), 72.
4. Friedman, A. N., Ogden, L. G., Foster, G. D., Klein, S., Stein, R., Miller, B., Hill, J. O., Brill, C., Bailer, B., Rosenbaum, D. R. and Wyatt, H. R., 2012. Comparative effects of low-carbohydrate high-protein versus low-fat diets on the kidney. Clinical Journal of the American Society of Nephrology, 7 (7), 1103–1111.
5. Juraschek, S. P., Appel, L. J., Anderson, C. A. M. and Miller, E. R., 2013. Effect of a high-protein diet on kidney function in healthy adults: Results from the OmniHeart trial. American Journal of Kidney Diseases, 61 (4), 547–554.
6. Martin, W. F., Armstrong, L. E. and Rodriguez, N. R., 2005. Dietary protein intake and renal function. 2. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1262767/
7. Poortmans, J. and Dellalieux, O., 2000b. Do regular high protein diets have potential health risks on kidney function in athletes? International journal of sport nutrition and exercise metabolism., 10 (1), 28–38. Available from: https://www.ncbi.nlm.nih.gov/pubmed/10722779
8. Antonio, J., Ellerbroek, A., Silver, T., Vargas, L., Tamayo, A., Buehn, R. and Peacock, C. A., 2016b. A high protein diet has no harmful effects: A One-Year crossover study in resistance-trained males. Journal of Nutrition and Metabolism, 2016, 1–5.
