Benefits
Helps maintain bone mineral density
In 389 postmenopausal women with osteopenia (bone density below normal but not osteoporosis), 54 mg per day of genistein aglycone for 24 months raised bone mineral density at the lumbar spine and femoral neck, while density fell in the placebo group. Both differences were highly statistically significant (P less than 0.001), and everyone in the trial also took calcium and vitamin D. This was a study in women already diagnosed with low bone density, and it comes from a single Italian centre that no other group has replicated.
Helps reduce menopausal hot flashes
In a 12 month randomized trial in early postmenopausal women, daily hot flushes fell by about 22 percent at 3 months, 29 percent at 6 months and 24 percent at 12 months compared with placebo. The benefit levelled off rather than building steadily, so 'progressive improvement' would overstate it. The study also included an estrogen-progestin therapy arm as a comparison, and it is a single trial from the same Italian group.
Supports mood and quality of life in postmenopause
In a two year randomized trial in postmenopausal women with osteopenia, those taking genistein reported better quality-of-life scores and fewer depression symptoms than those on placebo. These were self-reported questionnaire outcomes in women enrolled for a bone study, not a trial of people being treated for depression, and genistein is not a treatment for depression or any other mood disorder.
Supports cardiometabolic risk markers
A two year randomized trial in postmenopausal women with osteopenia reported changes in some blood markers used to estimate cardiovascular risk. These are laboratory measurements, not heart attacks, strokes or any other real-world event, so this does not show that genistein protects the heart or prevents heart disease. It is also the same single Italian research group as the other trials here.
Provides selective phytoestrogen activity
Genistein binds estrogen receptors and prefers the beta subtype, which is the leading explanation for its effects on bone and hot flushes in the trials above. Preferring one receptor subtype is still hormonal activity. It should not be taken as evidence that genistein is safe for breast, uterine or ovarian tissue, because none of the studies cited on this page tested that question.
Mechanism of action
Selective estrogen receptor beta agonism
Genistein binds estrogen receptors with higher affinity for the beta subtype than the alpha subtype. This is the proposed reason it can copy some effects of estrogen in bone and blood vessels, and it means genistein is hormonally active rather than hormone free.
Bone remodeling balance
In laboratory and animal work, genistein acting through the beta estrogen receptor appears to encourage the cells that build bone and quiet the cells that break it down. This is the leading explanation for the bone density results seen in the human trial, but it was not measured directly in the women who took part.
Tyrosine kinase and signaling modulation
In cell studies, genistein also blocks certain enzymes called tyrosine kinases and changes signaling inside cells. This is test tube biology only. None of the human trials cited on this page measured anything of the kind, and it says nothing about what genistein does to cancer in people.
Antioxidant and anti-inflammatory activity
In test tube and animal studies, genistein neutralizes reactive oxygen species and dampens inflammatory signaling. This is one proposed explanation for the blood marker changes seen in the cardiovascular risk trial, and it has not been confirmed as the actual mechanism in people.
Clinical trials
Multicenter, randomized, double-blind, placebo-controlled trial; 54 mg/day genistein aglycone vs placebo for 24 months, all participants receiving calcium and vitamin D.
389 osteopenic postmenopausal women with low femoral neck bone mineral density.
At 24 months bone mineral density rose on genistein and fell on placebo at both sites: lumbar spine +0.049 versus -0.053 g/cm2, and femoral neck +0.035 versus -0.037 g/cm2, both with P less than 0.001. Published in Annals of Internal Medicine, this is a large, long and well conducted trial and the strongest single piece of evidence on this page. Its main limitation is that it comes from one Italian research group and has not been independently repeated.
Randomized, double-blind, EPT- and placebo-controlled study; 54 mg/day genistein vs estrogen-progestin therapy vs placebo for 12 months.
90 healthy early postmenopausal women aged 47–57.
Compared with placebo, daily hot flushes fell by an average of 22% at 3 months, 29% at 6 months and 24% at 12 months in the genistein group. The benefit levelled off rather than continuing to grow. This is one trial, from the same Italian group as the bone studies, and how genistein compared with the estrogen-progestin arm is not reported here.
Two-year randomized, double-blind, placebo-controlled study evaluating quality of life and depression symptoms; 54 mg/day genistein with calcium and vitamin D vs placebo.
Osteopenic postmenopausal women enrolled in the multi-center genistein bone study.
Over two years, women with osteopenia taking genistein reported better quality-of-life scores and fewer depression symptoms than those on placebo. Both were self-reported questionnaires collected in a trial designed around bone density, and none of these women were being treated for clinical depression.