Your Muscles Want More Protein, But Not *That* Much More: Tiny Gains, Big Questions

Overview

Paper Summary › Explain Like I'm Five › Conflicts of Interest › Identified Limitations › Rating Explanation › Good to know › Topic Hierarchy › File Information ›

Paper Summary

Paperzilla title

This systematic review and meta-analysis investigated if increased daily protein intake improves lean body mass (LBM), muscle strength, and physical function in healthy adults. It found that additional protein, particularly with resistance exercise, leads to small extra gains in LBM and lower body strength for younger adults at higher protein intakes (≥1.6 g/kg/day). However, effects on bench press strength, handgrip strength, and physical function were mostly trivial or unclear, with low certainty of evidence due to high heterogeneity and risk of bias in the included studies.

Explain Like I'm Five

Eating a bit more protein can help your muscles grow a tiny bit and get a little stronger, but mostly if you also lift weights. For other things like how fast you can move or how strong your grip is, more protein doesn't seem to help much, or we're just not sure yet.

Possible Conflicts of Interest

Stuart M. Phillips is an inventor on a patent held by Exerkine Corporation and an unpaid member of the scientific advisory board of Enhanced Recovery™. Philip J. Atherton, Francesco Landi, Maria Camprubi Robles, Michelle Braun, and Sandra Naranjo-Modad have received research funding, honoraria, or are employed by nutrition companies (Abbott Nutrition, Fresenius-Kabi, Ajinomoto Co., Nutricia, International Flavors & Fragrances, Givaudan). The research itself was funded by the International Life Science Institute (ILSI Europe), an industry-funded organization.

Identified Limitations

Low Number of Studies for Certain Outcomes

The review frequently cites a 'low number of studies' for handgrip strength, physical performance tests, and specific age or protein intake subgroups, limiting the certainty of evidence and the possibility of drawing firm conclusions in these areas.

Increased Heterogeneity Across Studies

Moderate to high heterogeneity was observed across studies for several outcomes (e.g., bench press strength, lower-body strength, physical function tests), making it challenging to draw consistent conclusions due to varied study protocols and results.

Risk of Bias Due to Poor Blinding

Approximately a quarter of the included studies had an increased risk of bias, often due to poor blinding of participants or staff, or missing information on randomization. This can inflate observed effects and reduce the reliability of the findings, especially in dietary interventions.

High Baseline Protein Intake in Control Groups

Around 80% of the studies reported control groups already consuming at least 1.2 g of protein/kg body weight/day, which is 50% higher than current RDA. This high baseline might obscure larger potential benefits of 'additional' protein for individuals starting with lower protein intakes.

Marginal Effects and Influences from Individual Studies for Older Subjects

The effects on older subjects were often marginal or heavily influenced by single studies, indicating that findings might not generalize well to the older population and suggesting a need for more targeted research.

Limited Studies on Protein Intervention Alone

Very few studies (only six) investigated increased protein intake without concurrent resistance exercise, making it difficult to isolate the independent effects of protein supplementation in healthy adults.

Predominant Focus on Animal-Based Protein

Most studies (65 out of 74) focused on animal-based protein sources, meaning the findings primarily reflect these types of protein, limiting generalizability to plant-based or mixed protein diets.

Rating Explanation

The paper is a well-conducted systematic review and meta-analysis, following rigorous guidelines. However, its conclusions are significantly limited by the quality of the underlying evidence, which suffered from high heterogeneity, risk of bias (poor blinding), and low study numbers for several outcomes and subgroups. The reported effects were often small, trivial, or unclear. Additionally, substantial conflicts of interest from industry funding and authors employed by nutrition companies reduce confidence in potentially favorable interpretations.

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Topic Hierarchy

Domain: Health Sciences

Field: Medicine

Subfield: Orthopedics and Sports Medicine

File Information

Original Title: Systematic review and meta-analysis of protein intake to support muscle mass and function in healthy adults

Uploaded: December 22, 2025 at 02:35 PM

Privacy: Public