Whey Protein

Whey protein isolate · Whey protein concentrate · Whey protein hydrolysate

Snapshot

Indications	Contraindications
Sarcopenia in older adults¹ Fat-free mass during weight loss² Postprandial glucose control³ Recovery after resistance training^4–9 Gestational diabetes glycemia^{10, 11}	Milk allergy¹² Hydrolyzed formula in milk allergy¹³

Whey protein, available as isolate, concentrate, and hydrolysate, is the soluble milk protein fraction left after cheese making. It is taken for concentrated, rapidly absorbed essential amino acids that support muscle protein synthesis. Older adults with sarcopenia use it for muscle mass and gait speed, and adults with obesity use it to preserve fat-free mass during weight loss.

In older adults with sarcopenia, one meta-analysis found whey protein increased muscle mass and gait speed, while handgrip strength improved only when combined with resistance training¹. Benefit is most consistent alongside resistance training^{14, 15}. In older adults, a 2026 small short-term trial of whey protein isolate increased gut microbiota diversity in those with low baseline diversity¹⁶. Whey protein products are on the market, mostly powders; see Form comparison.

Health Canada lists milk allergy as a contraindication on licensed products, since whey is a milk protein¹². A narrative review urges caution with protein intake in hepatic or renal impairment¹⁷.

Last updated October 15, 2026. Read how we make monographs.

In the full monograph

77 sources, 64 studies

When to useThe situations practitioners use it for, each with the reason and the study behind it.
SafetyWho should avoid it, who needs extra care, and the side effects reported in studies.
Protocol notesThe doses used in studies, how and when they were taken, and how the forms on the market compare.
How it worksWhat it is and how it works in the body, in plain terms.
Published studiesThe studies behind each use, popular claims checked against them, and trials still under way.
Word of mouthWhat patients and practitioners report online, kept separate from the clinical evidence.
Clinical perspectiveA closing read of where the evidence is solid, where it is thin, and what has not been studied.

Snapshot

In the full monograph

Sources