What is it? Overview Usage Side Effects and Warnings

What is Genistein?

Genistein, a naturally occurring chemical present in soy, has attracted scientific interest for its possible benefits in cancer and heart disease prevention. Genistein is a type of chemical called a phytoestrogen—an estrogen-like substance present in some plants. There are two main types of phytoestrogens: isoflavones and lignans . Soy is the most abundant source of isoflavones, with genistein the most abundant isoflavone in soy. Red clover is also a good sourse of genistein.

Like other phytoestrogens, genistein can work in two ways: either by increasing or decreasing the effects of estrogen. This happens because genistein binds to special sites on cells called estrogen receptors. Genistein stimulates these receptors, but not as strongly as real estrogen; at the same...

Double-blind, placebo-controlled studies have found that genistein may be helpful for preventing heart disease 1 and preventing or treating osteoporosis . 2 Genistein may additionally improve blood sugar control in people with pre- diabetes . 3 Weaker evidence suggests potential benefits in cancer prevention , 4 cancer treatment , 5 and amyotrophic lateral sclerosis (ALS). 6 Isoflavone mixtures containing genistein have undergone considerably more study than genistein alone. Mixed isoflavones have shown promise for most of the conditions just mentioned, as well as menopausal symptoms and cyclic mastalgia .

Safety Issues

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Genistein is extracted from soy

Most safety studies that have implications for genistein involved mixed isoflavones from soy or red clover. For more information, see the Safety Issues section of the Isoflavone article.

Regarding genistein alone, one large study reported that genistein caused significant gastrointestinal side effects in almost 20% of participants. 7

Additionally, some evidence suggests that genistein might impair immunity. One study in mice found that injected genistein has negative effects on the thymus gland (an organ that is important for immunity) and also causes changes in the prevalence of various white blood cells consistent with impaired immunity. 8 Although the genistein was injected rather than administered orally, the blood levels of...