Protein intake and your kidneys: does high protein harm kidney function?

Eating a lot of protein does not damage the kidneys in healthy people. That is the short answer, and it is backed by several studies. A high-protein diet can shift some blood values slightly, but that is different from damage. If you already have a kidney condition, the story is different.

Few fitness myths are as stubborn as this one. "Too much protein wrecks your kidneys" is something I have heard for years, usually without a source attached.

Does high protein harm your kidneys?

In people with healthy kidneys, there is no evidence that a high-protein diet damages kidney function. A systematic review and meta-analysis found no difference in kidney function between healthy adults eating high or low protein (Devries, 2018). Your kidneys adapt to a higher protein intake.

In a study of trained men who ate a lot of protein for a full year, no harmful effects on kidney or liver values were seen (Antonio, 2016).

Where does the myth come from?

The myth arises because protein does change your kidney values, without anything breaking. More protein means more waste products such as urea, and your kidneys filter a bit harder for a while. In healthy people that is normal physiology, not overload.

The advice to limit protein comes from the care of people with an existing kidney condition. That is a different group from a healthy lifter.

The difference between "the value changes" and "the organ gets damaged" is exactly where this myth goes wrong.

What does protein do to your blood values?

A high-protein diet can raise your urea and sometimes your creatinine slightly. A high-protein meal shortly before the draw can amplify that effect. That rise reflects your diet, not your kidney function.

To judge your kidneys apart from your diet, cystatin C helps, as it does not move with muscle mass (Baxmann, 2008).

Who should be cautious?

If you have an existing kidney condition, diabetes or high blood pressure, a high protein intake is not an automatic choice. For that group different trade-offs apply, which you make together with your doctor. The evidence on "safely high protein" is about people with healthy kidneys.

If you are unsure about your starting point, have your kidney values checked before you push your protein up sharply. Our kidney health blood test gives you that baseline.

Read on: blood values for strength athletes, high creatinine from muscle mass and creatine and your blood values.

My advice: if your kidneys are healthy, you do not need to fear your protein intake. Test on a calm day, drink enough, and discuss a persistent deviation with your GP.

References

1. Devries MC, Sithamparapillai A, Brimble KS, 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. The Journal of Nutrition. 2018. PMID: 30383278.
2. Antonio J, Ellerbroek A, Silver T, et al. A high protein diet has no harmful effects: a one-year crossover study in resistance-trained males. Journal of Nutrition and Metabolism. 2016. PMID: 27807480.
3. Baxmann AC, Ahmed MS, Marques NC, et al. Influence of muscle mass and physical activity on serum and urinary creatinine and serum cystatin C. Clinical Journal of the American Society of Nephrology. 2008. PMID: 18235143.

Disclaimer

Every blood test result includes a professional assessment by a BIG-registered doctor. This article gives general information and is not a substitute for medical advice. A blood test is a tool to walk into the conversation with your GP better informed, not a diagnosis in itself. For treatment decisions, discuss your results with your GP.