Supplement analysis backed by scientific evidence · PT

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Strong evidencePhysical performance

Whey Protein Isolate

A filtered whey with roughly 90% protein and very little lactose or fat. Protein supplementation reliably adds muscle mass and strength when total intake is otherwise low; the isolate's advantage over cheaper concentrate is convenience and digestibility, not extra muscle.

Evidence last reviewed: August 2026

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What the science says

  • Muscle mass and strength with resistance training Strong evidence

    A meta-analysis and meta-regression of 49 randomized trials with 1,863 participants found that protein supplementation significantly increases gains in fat-free mass and one-repetition-maximum strength during resistance training, with benefit plateauing around 1.6 g/kg/day of total protein.

  • Sarcopenia in older adults Moderate evidence

    Two systematic reviews with meta-analysis of randomized trials found that whey protein combined with resistance exercise improves muscle mass and strength in older adults with sarcopenia. Effects are real but modest and depend on the training stimulus.

  • Recovery of muscle function after training Moderate evidence

    A systematic review and meta-analysis found whey protein accelerates the temporal recovery of muscle function after resistance exercise, with the effect clearest in the first 24–48 hours.

Dosage & safety

Studied dose20–40 g per serving, typically after training or as needed to reach a total intake of about 1.6 g of protein per kg of body weight per day. Older adults often need the higher end per serving.
SafetySafe for most people. Isolate contains far less lactose than concentrate, so it is usually tolerated by those with lactose intolerance, but it is not suitable for milk protein allergy. Very high intakes offer no extra benefit and displace other foods; people with kidney disease should check with a doctor.

Scientific references

Where to buy

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