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Supplements

Protein Supplementation

A practical way to close a dietary protein gap, with the clearest muscle benefit when paired with resistance training rather than used alone.

Strong
Evidence rating
Evidence review

What the evidence says

Protein powder is food in a concentrated format, not a separate anabolic shortcut. Its main value is convenience when ordinary meals do not provide enough high-quality protein to support training, recovery, or a clinically identified nutrition need.[5]

A meta-analysis of 49 trials in healthy adults found that protein supplementation added small gains in strength and fat-free mass during prolonged resistance training. Benefits plateaued around a total intake near 1.6 g/kg/day in that dataset, so adding more after needs are met is unlikely to keep producing proportional gains.[1]

Older adults show a similar interaction with exercise. A 2024 network meta-analysis of 78 trials found improvements across muscle, grip strength, and walking outcomes, while a sarcopenia-focused whey review found small gains that often did not exceed minimally important clinical differences.[2][3]

The result depends on total diet, training, health, and product. Protein cannot replace the progressive overload that drives adaptation, and isolated supplements may add little for someone already meeting needs through food.[1][5]

A kidney-function meta-analysis found no adverse change attributable to higher-protein diets in healthy adults, but that conclusion does not apply automatically to chronic kidney disease. Clinical kidney or liver disease, frailty, and unintended weight loss call for individualized nutrition guidance.[4]

Potential benefits

  • Modestly augments lean-mass and strength gains during resistance training.[1]
  • Offers a convenient way to meet protein needs when appetite, schedule, or food access makes meals insufficient.[5]

Side effects and cautions

  • Some products cause bloating, nausea, diarrhea, or intolerance to milk-derived ingredients or sweeteners.[3]
  • People with kidney disease should not infer safety from healthy-adult high-protein trials and may need a clinician-set target.[4]
How we scored it

Evidence breakdown

Large meta-analyses show small additional gains in muscle and strength during resistance training, including in older adults, while benefits shrink when baseline intake is already adequate.

Clinical relevanceHigh

Outcomes include lean mass, strength, walking speed, and physical function.

Study qualityHigh

Dozens of randomized resistance-training trials have been pooled across populations.

Safety dataModerate

Healthy-adult trials are reassuring, but kidney disease and undernutrition require individualized targets.

References

Full source list

  1. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults

    British Journal of Sports Medicine · 2018

  2. Comparative Efficacy of Different Protein Supplements on Muscle Mass, Strength, and Physical Indices of Sarcopenia among Older Adults Undergoing Resistance Training

    Nutrients · 2024

  3. Effectiveness of Whey Protein Supplementation during Resistance Exercise Training on Skeletal Muscle Mass and Strength in Older People with Sarcopenia

    Nutrients · 2023

  4. Changes in Kidney Function Do Not Differ between Healthy Adults Consuming Higher- Compared with Lower- or Normal-Protein Diets

    The Journal of Nutrition · 2018

  5. Dietary Supplements for Exercise and Athletic Performance: Health Professional Fact Sheet

    NIH Office of Dietary Supplements · 2024