Research

Hormonal

Whey protein stimulates muscle protein synthesis (MPS) to a greater extent than casein or soy due to its rapid digestibility and high leucine content, leading to superior gains in lean body mass and strength when combined with resistance training.

If you lift weights, choose whey protein for your post-workout shake. It digests fast and spikes leucine, which triggers muscle growth better than slower proteins like casein. Aim for about 25 grams of whey post-workout. If you are older, you might need 35-40 grams to get the same benefit because your body becomes less sensitive to protein as you age.

GoodSupportsHIGH confidence
Whey protein has been shown to stimulate MPS to a greater extent than casein and soy protein at rest and following exercise in young and older individuals... The differential MPS response to protein feeding is a function of the quality of the ingested protein... Upon ingestion whey protein is rapidly digested and, since it is acid-soluble, it exits the stomach rapidly resulting in a pronounced rise in blood AA, which is thought to be critical to the stimulation of MPS.
Michaela C. Devries et al. · Journal of Food Science · 2015

Why this rating

Based on a review of multiple RCTs and meta-analyses, though some conflicting trials exist.

Source

Supplemental Protein in Support of Muscle Mass and Health: Advantage Whey

Michaela C. Devries et al. · Journal of Food Science · 2015

DOI 10.1111/1750-3841.12802

narrative_reviewCited 325×
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DOI resolved against Crossref · corpus check 2026-06-10

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