The myth
High protein damages your kidneys
The belief that high-protein diets harm the kidneys or are dangerous in healthy people.
High protein is safe for healthy kidneys, and most people are eating too little, not too much.
What the evidence shows
- 1
Healthy kidneys handle it
The kidney-damage concern comes from a real finding, but only in people who already have chronic kidney disease, where protein restriction to 0.6 to 0.8 g/kg/day is genuinely recommended to slow progression. In healthy individuals, no evidence links intakes up to 2.2 g/kg/day with kidney harm.
- 2
Heart risk is a non-issue
A large prospective analysis found high total protein intake is actually associated with lower cardiovascular disease morbidity (relative risk 0.88), and scaling protein from 10% to 25% of total calories produced no significant change in coronary heart disease or hypertension risk.
- 3
Most people undershoot the target
The RDA of 0.8 g/kg/day is a minimum to prevent deficiency, not an optimal target. Athletes need 1.2 to 1.7 g/kg/day, older adults need 1.0 to 1.5 g/kg/day to fight sarcopenia, and during a calorie deficit, eating 1.75 g/kg/day preserved 0.3 kg more lean mass and shed 0.4 kg more fat compared to eating just 1.0 g/kg/day.
- 4
The muscle-building ceiling is clear
Research consistently places the plateau for resistance-training gains at around 1.6 g/kg/day for most people, with a statistical upper bound of 2.2 g/kg/day for advanced trainees. Eating beyond that is not dangerous, it is simply unnecessary for muscle growth.
The myth has one legitimate root: protein restriction genuinely matters for people with existing chronic kidney disease or type 2 diabetes with CKD. Extrapolating that clinical caution to healthy people is where the evidence breaks down entirely.
If your kidneys are healthy, aim for 1.6 g/kg/day of protein to support muscle and body composition, and know that going higher carries no kidney risk.
Not one study. 200 of the strongest findings, across 8 areas of science, weigh in.
- Macro partitioning75
- Hormonal47
- Mixed28
- Energy balance25
- Metabolic adaptation11
The receipts
The underlying findings, each linked to its source paper.
What refutes it149
Total daily protein intake of 1.6 g/kg/day is sufficient for maximizing resistance training-induced muscle gains, with an upper confidence interval of 2.2 g/kg/day.
Macro partitioning · ev 5/5Resistance exercise training combined with sufficient dietary protein intake acts synergistically to maximize skeletal muscle hypertrophy, with protein intake saturating around 1.6 g/kg/day for general populations and potentially requiring 2.0-2.2 g/kg/day for resistance-trained individuals.
Macro partitioning · ev 5/5Severely protein-deficient diets (2–3% energy) induce lean body mass loss and metabolic imbalance, whereas adequate protein intake (0.66 g/kg/d minimum) is a prerequisite for maintaining muscle, bone, and physiological function.
Mixed · ev 5/5Older adults require higher total protein intakes (1.0–1.5 g/kg/d) and higher EAA/leucine density to overcome anabolic resistance and maximize muscle protein synthesis.
Hormonal · ev 5/5Protein needs for energy-restricted resistance-trained athletes are likely 2.3-3.1g/kg of FFM scaled upwards with severity of caloric restriction and leanness.
Energy balance · ev 5/5Older individuals should ingest at least 1.2 g of protein/kg/day to offset muscle atrophy.
Energy balance · ev 5/5
Findings that support it51
Protein supplementation augments strength and hypertrophy.
Mixed · ev 5/5Insulin infusions without amino acids resulted in a progressive decrement in leucine Ra (14 to 45%), NORd (16-41%), and OXRd (3-56%) compared with basal values.
Hormonal · ev 5/5The infusion of amino acids resulted in an additional reduction in endogenous Ra and a blunting of NORd reduction at each dose of insulin.
Hormonal · ev 5/5Hypoaminoacidemia associated with insulin treatment blunts the responsiveness of insulin's suppression of protein breakdown.
Hormonal · ev 5/5The adequate dietary protein intake for individuals over the age of 19 is approximately 0.8-0.9 g protein per kg of body weight per day.
Energy balance · ev 5/5No additional dietary protein is suggested for healthy adults undertaking resistance or endurance exercise.
Energy balance · ev 5/5
How findings are graded and citations verified. Methodology →