Will Eating Protein Blow Up My Kidneys?

Will Eating Protein Blow Up My Kidneys?

If you have healthy kidneys the answer looks to be a fairly resounding NO [1-3].

It is important to note that even with all the noise on social media about this topic…

“Neither the Institute of Medicine nor the World Health Organization acknowledges that protein intake contributes to functional declines in renal function with age.”

-Traylor et al. 2018 [4]

But, in order to understand this debate we have to talk through the rationale for why this misplaced ideology even exists in the first place.

Kidney function on a standard lab panel is primarily assessed by a value called Estimated Glomerular Filtration Rate or eGFR. The key word there is estimated. There are multiple equations that do this, but the primary equations are the CKD-EPI Creatinine (2009) and MDRD equation and these methods pretty much just use serum creatinine and age.

This is a huge problem for athletes because serum creatinine directly correlates with muscle mass and this means as you build more muscle your serum creatinine will likely increase as muscle mass accounts for as much as 98% of your creatine stores [5-7].

Hold up, more muscle is a bad thing?

For the average American Absolutely NOT.

The loss of muscle mass independently relates to hospitalization and death and the preservation of muscle mass has been found to be protective of all-cause mortality at every BMI category [8-10]

Serum creatinine has even been studied as a way to indirectly track muscle mass at the population level and has been found to predict mortality in critically ill patients and even predict type 2 diabetes risk [11, 12]. Even more wild is that an equation utilizing the combination of serum creatinine and another kidney function marker called Cystatin C has been found to estimate muscle mass and this equation may be useful in identifying sarcopenia (loss of muscle tissue) [13]!

Intense physical activity and strength training can also transiently and chronically increase creatinine markers and no one in their right mind is telling Americans to exercise less because of these findings [14-18]. Creatine supplementation can also raise serum creatinine levels and both long and short-term studies have overwhelmingly found NO adverse effects on kidney function [19-25].

So, yes your serum creatinine could up and your estimated GFR could then go down from eating more protein, training, and gaining muscle. Unfortunately, if you go to the wrong physician who hasn’t read a research paper in the last decade they may freak you out. BUT…

“Increased kidney size and GFR are not linked to kidney damage and disease. Together, our meta-analysis and other lines of evidence provide no evidence that the increase in GFR in response to an increase in blood solute load increases the risk of chronic kidney disease (CKD).”

-Devries et al. 2018 [1]

In this specific case you can ask for a Cystatin C marker because this value seems to be unaffected by diet or muscle mass [6, 7, 26, 27].

In fact, likely anyone who is between 45 and 60 on an eGFR should have this testing done anyways [28].

So are higher protein intakes in healthy individuals bad for our health?

No and if this increased protein intake is coupled with an increase in muscle mass from exercise and a loss of adipose tissue from a caloric deficit and increased diet quality - HELL TO THE NO!

In fact, severely blasting down protein in individuals with normal kidney function may be bad for their long-term health.

“Among participants with normal kidney function, we found that lower levels of dietary protein intake (<0.6 g/kg bodyweight/day) were associated with worse survival, whereas higher dietary protein intakes levels were not associated with higher mortality risk.”

-Narasaki et al., 2021 [3].

Ironically, this negative finding from prospective observational research is likely confounded by dietary protein’s positive association with muscle mass and muscle mass’s seemingly protective effect on all-cause mortality [9, 10, 29]. It is important to note here that just increasing your dietary protein intake without a sufficient exercise stimulus and progressive overload is NOT going to magically defy the SAID principle and add muscle to your frame or spare muscle mass on a diet [30-32].

Now, if you have been diagnosed with Chronic Kidney Disease (CKD) this low protein argument becomes even more nuanced and I would highly highly recommend reading the 2018 meta-analysis by Yan and colleagues and discussing this paper with your provider [33].

If I was diagnosed with CKD and had an adequate amount of muscle, I would likely reduce my protein intake and try to maintain muscle through a sufficient training stimulus. However, diabetes and high blood pressure are the most common causes of CKD [34], and thus if a higher protein diet helps someone who is at risk for diabetes and/or high blood pressure lose body fat and gain muscle it may in fact be preventive against chronic kidney disease!

REFERENCES:

1. Devries, M.C., et al., Changes in Kidney Function Do Not Differ between Healthy Adults Consuming Higher- Compared with Lower- or Normal-Protein Diets: A Systematic Review and Meta-Analysis. J Nutr, 2018. 148(11): p. 1760-1775.

2. Berryman, C.E., et al., Diets higher in animal and plant protein are associated with lower adiposity and do not impair kidney function in US adults. Am J Clin Nutr, 2016.

3. Narasaki, Y., et al., Dietary protein intake, kidney function, and survival in a nationally representative cohort. Am J Clin Nutr, 2021.

4. Traylor, D.A., S.H.M. Gorissen, and S.M. Phillips, Perspective: Protein Requirements and Optimal Intakes in Aging: Are We Ready to Recommend More Than the Recommended Daily Allowance? Adv Nutr, 2018. 9(3): p. 171-182.

5. Banfi, G., M. Del Fabbro, and G. Lippi, Serum creatinine concentration and creatinine-based estimation of glomerular filtration rate in athletes. Sports Med, 2009. 39(4): p. 331-7.

6. Baxmann, A.C., et al., Influence of muscle mass and physical activity on serum and urinary creatinine and serum cystatin C. Clin J Am Soc Nephrol, 2008. 3(2): p. 348-54.

7. Chew-Harris, J.S., et al., The relative effects of fat versus muscle mass on cystatin C and estimates of renal function in healthy young men. Ann Clin Biochem, 2013. 50(Pt 1): p. 39-46.

8. Mitchell, W.K., et al., Sarcopenia, dynapenia, and the impact of advancing age on human skeletal muscle size and strength; a quantitative review. Front Physiol, 2012. 3: p. 260.

9. Garcia-Hermoso, A., et al., Muscular Strength as a Predictor of All-Cause Mortality in an Apparently Healthy Population: A Systematic Review and Meta-Analysis of Data From Approximately 2 Million Men and Women. Arch Phys Med Rehabil, 2018. 99(10): p. 2100-2113 e5.

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11. Hashimoto, Y., et al., Creatinine to Body Weight Ratio Is Associated with Incident Diabetes: Population-Based Cohort Study. J Clin Med, 2020. 9(1).

12. Thongprayoon, C., W. Cheungpasitporn, and K. Kashani, Serum creatinine level, a surrogate of muscle mass, predicts mortality in critically ill patients. J Thorac Dis, 2016. 8(5): p. E305-11.

13. Kim, S.W., et al., A New Equation to Estimate Muscle Mass from Creatinine and Cystatin C. PLoS One, 2016. 11(2): p. e0148495.

14. Touchberry, C.D., et al., Training alterations in elite cyclists may cause transient changes in glomerular filtration rate. J Sports Sci Med, 2004. 3(YISI 1): p. 28-36.

15. Bongers, C., et al., Impact of acute versus prolonged exercise and dehydration on kidney function and injury. Physiol Rep, 2018. 6(11): p. e13734.

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17. Spada, T.C., et al., High intensity resistance training causes muscle damage and increases biomarkers of acute kidney injury in healthy individuals. PLoS One, 2018. 13(11): p. e0205791.

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19. Williamson, L. and D. New, How the use of creatine supplements can elevate serum creatinine in the absence of underlying kidney pathology. BMJ Case Rep, 2014. 2014.

20. Gualano, B., et al., Effects of creatine supplementation on renal function: a randomized, double-blind, placebo-controlled clinical trial. Eur J Appl Physiol, 2008. 103(1): p. 33-40.

21. de Guingand, D.L., et al., Risk of Adverse Outcomes in Females Taking Oral Creatine Monohydrate: A Systematic Review and Meta-Analysis. Nutrients, 2020. 12(6).

22. Buford, T.W., et al., International Society of Sports Nutrition position stand: creatine supplementation and exercise. J Int Soc Sports Nutr, 2007. 4: p. 6.

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24. Poortmans, J.R. and M. Francaux, Long-term oral creatine supplementation does not impair renal function in healthy athletes. Med Sci Sports Exerc, 1999. 31(8): p. 1108-10.

25. de Souza, E.S.A., et al., Effects of Creatine Supplementation on Renal Function: A Systematic Review and Meta-Analysis. J Ren Nutr, 2019. 29(6): p. 480-489.

26. Banfi, G., et al., Metabolic markers in sports medicine. Adv Clin Chem, 2012. 56: p. 1-54.

27. Kazama, J.J., et al., Serum cystatin C reliably detects renal dysfunction in patients with various renal diseases. Nephron, 2002. 91(1): p. 13-20.

28. Cheuiche, A.V., et al., Performance of Cystatin C-Based Equations for Estimation of Glomerular Filtration Rate in Diabetes Patients: A Prisma-Compliant Systematic Review and Meta-Analysis. Sci Rep, 2019. 9(1): p. 1418.

29. Alexandrov, N.V., et al., Dietary Protein Sources and Muscle Mass over the Life Course: The Lifelines Cohort Study. Nutrients, 2018. 10(10).

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31. Hill, A.M., et al., Type and amount of dietary protein in the treatment of metabolic syndrome: a randomized controlled trial. Am J Clin Nutr, 2015. 102(4): p. 757-70.

32. Backx, E.M., et al., Protein intake and lean body mass preservation during energy intake restriction in overweight older adults. Int J Obes (Lond), 2016. 40(2): p. 299-304.

33. Yan, B., et al., Effect of diet protein restriction on progression of chronic kidney disease: A systematic review and meta-analysis. PLoS One, 2018. 13(11): p. e0206134.

34. Webster, A.C., et al., Chronic Kidney Disease. Lancet, 2017. 389(10075): p. 1238-1252.