Genistein

What is genistein?

Genistein is one of the main isoflavones in soybeans. Isoflavones are plant compounds with a structure similar to the hormone estrogen, which is why they are sometimes called phytoestrogens. Genistein is present in foods such as tofu, tempeh, miso and soy milk, and it is also available as a purified or concentrated ingredient in supplements, usually derived from soy.

What the research says

Most research on soy looks at whole foods, soy protein or mixed isoflavone extracts rather than genistein alone. The National Center for Complementary and Integrative Health notes that soy isoflavones probably have a beneficial effect on bone density in postmenopausal women and may modestly lower blood pressure, while effects on blood sugar control in people with diabetes remain uncertain.

For liver and metabolic outcomes specifically, the evidence for genistein is thin. In a randomized, double-blind trial of adults with nonalcoholic fatty liver disease, 250 mg of genistein a day for eight weeks, alongside diet and activity advice, lowered insulin, insulin resistance, some inflammatory markers, waist-to-hip ratio and body fat percentage compared with placebo. It did not significantly change the liver enzymes ALT and AST. This was a single, small, short study, and the dose was relatively high.

There is no good human evidence that genistein at the low, undisclosed amounts typical of multi-ingredient blends helps burn liver fat or produces weight loss.

How it’s used in supplements

Genistein is sold as a standalone supplement and as part of soy isoflavone products for menopause and bone health. In liver and weight blends, it is usually one of many ingredients without a stated amount, which makes comparison with the 250 mg used in research impossible.

NCCIH reports that concentrated soy isoflavone extracts have been used safely in studies for up to six months, and that soy can cause digestive side effects and allergic reactions in people allergic to soy. Because genistein has estrogen-like activity, people with a history of hormone-sensitive conditions, those taking hormonal medications, and anyone pregnant or breastfeeding should talk to a doctor before taking concentrated isoflavones.

Bottom line: genistein is a well-known soy isoflavone with broader research in bone and menopausal health. For liver fat and weight, the evidence rests largely on one small eight-week trial at 250 mg a day. That is not enough to support claims that genistein burns liver fat, especially at the small, undisclosed amounts found in multi-ingredient blends. Eating soy foods such as tofu, tempeh or edamame is a low-risk way to include isoflavones in a balanced diet.