Protein Guide
Does high protein damage your kidneys?
This is probably the most repeated concern about high-protein diets — and one where the evidence for healthy people is much clearer than the rumour suggests.
Where the concern came from
Protein metabolism produces nitrogen waste, which the kidneys filter out. In people who already have chronic kidney disease, reducing protein intake can slow the decline in kidney function. That clinical finding — real and well-established in kidney patients — got generalized into a warning for everyone.[1]
What happens in healthy kidneys
Higher protein intake does increase glomerular filtration rate, the rate at which kidneys filter blood. But that's a normal functional adaptation to a higher workload, not damage — in the same way that muscles adapt to heavier training. Controlled trials in healthy adults consuming high-protein diets have not shown deterioration in kidney function.[2]
Who should actually limit protein
People with diagnosed chronic kidney disease, reduced kidney function, or a single kidney should follow protein targets set by their doctor or renal dietitian — not general fitness guidance. The point isn't that protein is harmless for everyone; it's that healthy kidneys and impaired kidneys are different situations.
If you have any reason to suspect reduced kidney function, that's a blood test question, not an internet question.
Frequently asked questions
Does high protein damage healthy kidneys?
In people with healthy kidneys, controlled trials have not shown that high protein intake causes kidney damage. The increase in filtration rate seen on higher-protein diets is a normal functional adaptation rather than injury.
Who does need to limit protein?
People with diagnosed chronic kidney disease or reduced kidney function should follow protein targets set by their doctor or renal dietitian, since lowering protein can slow the decline in kidney function in that group.
How much protein is too much?
For healthy adults there is no well-established intake at which protein becomes harmful. Most benefit plateaus around 1.6-2.2 g/kg of body weight per day for people who train, so higher intakes mainly displace other nutrients rather than adding benefit.
Keep reading: How much protein per day · Common nutrition myths · Protein for muscle growth