Soy Isoflavones
Soy isoflavones are plant compounds in soybeans, mainly genistein, daidzein and glycitein. Because they resemble estrogen in structure, they are called phytoestrogens.
Also listed as Genistein, Genistin, Daidzein, Daidzin
What it is studied for
The strongest rated effects first. Bars show the size of the effect, the letter grades the evidence, and each rating lists the studies behind it.
Are isoflavones a form of estrogen?
Isoflavones are plant compounds with a structure resembling estrogen and can exert weak estrogen-like effects. This explains the interest in menopause symptoms, but does not make an isoflavone capsule equivalent to hormone treatment. 1 2
Key studies
The most recent publications linked to Soy Isoflavones's ratings.
Why people take it
SuppCo community snapshot, 2026-09-28. Reasons for use are not evidence that it works.
Questions people ask
Will isoflavones stop hot flashes?
Some trials show fewer episodes, but effects vary and the average benefit may be small. 1 3
Are they proven to restore estrogen?
The hormone review does not show a consistent, clinically established estrogen-restoring effect. 4
Can I use 100 mg indefinitely?
No indefinite safety conclusion follows from BfR’s guidance, which includes a ten-month duration boundary. 2
Should breast-cancer survivors avoid all soy?
NCCIH distinguishes soy foods, which appear safe, from concentrated isoflavone supplements whose safety is uncertain in this group. 5
Soy