Soy Protein

Soy protein isolate · Soya protein

Snapshot

Indications	Contraindications
Muscle strength with training¹ Lean mass in active adults² Low-density lipoprotein cholesterol^{3, 4} Type 2 diabetes control^5–7 Metabolic syndrome^5–7 Inflammatory markers^8–11 Predialysis kidney disease markers¹²	Soy allergy¹³ Pregnancy or nursing¹³

Soy protein is the protein fraction of soybeans, sold as isolate or concentrate powders that supply a well-balanced amino acid profile comparable to animal protein¹⁴. It is taken mainly as a plant-based protein source to support lean mass alongside resistance training. Further uses are lowering cholesterol and supporting glycemic control in type 2 diabetes and metabolic syndrome⁵. Typical users are vegans, athletes, and older adults who avoid animal protein.

A meta-analysis found soy and whey gave similar gains in strength and lean mass with resistance training¹. A 2026 meta-analysis in young adults found no effect of either protein on lean mass¹⁵. Meta-analyses of controlled trials show small reductions in low-density lipoprotein cholesterol^{3, 4}. In a 2023 laboratory bioassay study, genistein and daidzein drove the estrogenic activity of soy protein isolates; it was not a human trial¹⁶. Products are mostly isolate powders; see Form comparison.

Soy allergy is the main contraindication, and many soy-containing labels carry an allergen statement¹³. Per product labels, users who take medications or have a medical condition are told to consult a doctor before use¹³.

Last updated October 16, 2026. Read how we make monographs.

In the full monograph

75 sources, 62 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.
InteractionsThe medicines and supplements it interacts with, the effect of each, and what labeling says to watch.
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