# Proof Narrative: High-protein diets above 1.6 g/kg body weight damage kidneys in healthy people.

## Verdict

**Verdict: DISPROVED**

This claim is false. Multiple large-scale research reviews consistently find that high-protein diets do not damage kidneys in healthy adults — and one large study found they may actually lower kidney disease risk.

## What was claimed?

The idea that eating a lot of protein — specifically more than 1.6 grams per kilogram of body weight per day — harms your kidneys is widely repeated in fitness and wellness circles. For a 75 kg (165 lb) person, that threshold works out to about 120 grams of protein per day, a level commonly reached by people following high-protein diets or athletes. If this claim were true, a large portion of people pursuing common dietary advice would be quietly damaging their kidneys.

## What did we find?

The research evidence against this claim is strong and consistent. A 2018 meta-analysis published in the *Journal of Nutrition* — the most direct test of the claim — pooled results from 28 randomized controlled trials involving 1,358 healthy adults. These were controlled experiments where researchers assigned participants to high- or normal-protein diets and measured kidney function before and after. The result: high-protein intake did not adversely affect the rate at which kidneys filter blood. The groups showed no meaningful difference in how kidney function changed over time.

A separate and independent 2018 systematic review in *Advances in Nutrition* reached the same conclusion, examining both controlled trials and observational studies in people consuming protein above the standard US dietary recommendation. The researchers found that higher protein intake was consistent with normal kidney function in healthy individuals.

Perhaps most striking is a 2024 meta-analysis that followed 148,051 people across six cohort studies and tracked who developed chronic kidney disease. Rather than finding harm, the study found that higher protein intake was associated with *lower* risk of kidney disease — for total protein, plant protein, and animal protein alike.

One counterargument worth addressing: high protein does cause the kidneys to filter at a slightly higher rate temporarily, a phenomenon called glomerular hyperfiltration. Some have speculated this could cause damage over time. But this is a normal physiological response, like a heart beating faster during exercise — not a sign of damage. Controlled trials have not found this mechanism to produce actual harm in healthy adults.

## What should you keep in mind?

This proof applies specifically to people with healthy kidneys. If you have existing kidney disease, the picture is different: clinical guidelines do recommend limiting protein for that population, and that recommendation is well-established. The claim conflates two distinct groups.

The 1.6 g/kg figure in the claim is not a kidney safety limit set by doctors or kidney disease specialists. It comes from sports nutrition research as an approximate ceiling for muscle-building benefits — a completely different question. No nephrology guideline treats it as a threshold beyond which kidneys are at risk.

The studies here, while large and well-designed, are mostly short to medium term. Some researchers have raised theoretical concerns about very long-term high protein intake, and those questions aren't fully settled. What is clear is that no controlled trial has demonstrated actual kidney damage in healthy adults.

## How was this verified?

This verdict is based on three independent systematic reviews and meta-analyses, all verified by retrieving the source documents directly and confirming the quoted conclusions. The full reasoning behind each source, the adversarial checks performed, and the logic connecting the evidence to the verdict are documented in [the structured proof report](proof.md) and [the full verification audit](proof_audit.md). To inspect or reproduce the verification process yourself, see [re-run the proof yourself](proof.py).