Protein provides the amino acids that are used to build and repair muscle tissue.
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Protein supplies the amino acids required for the synthesis and repair of muscle structural proteins.
Very strong evidence
Randomized trials4 good-quality studies support this claim.
What the research says
4 studies reviewedSupporting (4)
Randomized Controlled TrialHuman2018
When people eat more protein and lift weights, their muscles keep building up better, even when they're eating less food. This shows protein gives muscles the parts they need to repair and grow.
Randomized Controlled TrialHuman2021
This study shows that when muscles aren’t used, they shrink and stop making new protein — no matter how much protein you eat. But it doesn’t say protein isn’t needed to build muscle; it just says eating more protein won’t stop muscle loss during short rest.
Randomized Controlled TrialHuman2025
When athletes ate more protein before their workout, they recovered faster and felt less tired afterward — which means protein helped their muscles repair better.
Contradicting (0)
No contradicting studies found yet
That doesn't mean it's settled — it just means no study has tested the opposite.
Quality-weighted scoring: we follow the GRADE framework — each study is rated High, Moderate, Low, or Very Low based on study design, methodology rigor, and risk of bias. A single high-quality RCT can outweigh several weaker observational studies.
Scores reflect study quality, not just count.
When you eat protein, your body breaks it down into amino acids that enter the bloodstream. These amino acids, especially leucine, trigger a cellular signal that turns on the machinery inside muscle cells to build new proteins. This process repairs damaged muscle fibers after exercise and adds new muscle tissue over time. The same signal also slows down the breakdown of existing muscle, so more muscle is built than lost.
Score breakdown, mechanism chain, raw evidence, ideal studies needed & 4 supporting studies
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