Is a high-protein diet bad for your kidneys?

The worry rests on a real observation stretched too far. In people who already have kidney disease, a high-protein diet can add load to the kidneys, and protein restriction is used in their care. That conclusion does not carry over to healthy kidneys.

A 2018 systematic review and meta-analysis (Devries et al.) pooled 28 controlled studies with more than 1,300 participants and found that higher protein intake did not worsen the kidneys' filtration rate (GFR) in healthy adults. A one-year crossover study in resistance-trained men (Antonio et al., 2016) had participants eat over 3 g of protein per kilogram of bodyweight per day, roughly four times the usual requirement, with no measurable effect on kidney or liver function. An earlier study in trained athletes (Poortmans and Dellalieux, 2000) found no decline in kidney function at intakes up to 2.8 g per kilogram.

The caveat is the familiar one: the evidence applies to healthy kidneys. If you already have kidney disease, diabetes with kidney involvement, or take medication that affects the kidneys, the picture changes, and your protein level belongs in a conversation with a doctor.

The myth grew from a narrower truth: in existing kidney disease, less protein helps, and that clinical guidance quietly got generalized to everyone. On top of that came the anxiety around protein powder, which sits on the same shelves, in the same kind of tubs, as more questionable products and inherits their reputation. A biological detail reinforces it: more protein can raise the creatinine value in a blood test, the same marker used to judge kidney function, so a harmless result can read like a warning. And an alarming headline about kidneys always travels further than a study that clears them. No one profits directly from the myth, but the precautionary instinct and the gut sense that too much of anything must be harmful keep it alive.

With healthy kidneys, the worry does not need to steer how much protein you eat. Around 1.6–2.2 g per kilogram of bodyweight per day is plenty for muscle and satiety, and sits well below the levels in the studies above. Drink water as usual. If you have known kidney disease or diabetes with kidney involvement, check your protein level with your doctor first. And tell your clinician you eat a high-protein diet if your creatinine value is being interpreted, just as with creatine. Work out your own protein target below.