Isoflavones are plant-based compounds found almost exclusively in beans, like soybeans, that mimic the action of the hormone estrogen. They may be useful in alleviating menopause symptoms or preventing osteoporosis in postmenopausal women.

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Foods rich in isoflavones may offer other health benefits in that they are both anti-inflammatory and antioxidant (meaning they prevent damage to a cell's DNA).1 Some studies have even suggested that isoflavones may help prevent heart disease or have cancer-fighting properties.

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Even so, the evidence supporting these health claims is generally weak.

This article describes the potential benefits of isoflavones, including what they do and how they work. It also lists some of the foods high in isoflavones along with the possible risks, side effects, and interactions.

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Hormone Effects of Isoflavones

Isoflavones are also known as phytoestrogens. That's because they are plant-based (phyto means "from plants") and they have a similar structure to estrogen. This allows isoflavones to bind with estrogen receptors.

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Depending on the hormone status of a person, isoflavones can affect a person in the same way that estrogen does by producing either estrogenic or antiestrogenic effects.

In studies involving isoflavone supplements for menopausal symptoms, some benefits have been shown, such as:2 

• Improving fatigue

• Improving irritability

• Decreasing hot flashes

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But, according to The Pharmaceutical Journal, although isoflavones are being marketed as an effective product for natural hormone replacement therapy (HRT), further research is needed. Consumers should not use isoflavones for long-term HRT until more research is able to prove the safety and efficacy of the products.

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Some case reports indicate that isoflavones in red clover help reduce hot flashes and anxiety during menopause. Although the herb is marketed as a dietary supplement called Promensil, the National Women’s Health Network reports that there is a lack of sufficient clinical research data to back up these claims.

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Medical Uses for Isoflavones

There are many common medical uses for isoflavones. Conditions that may improve with the use of isoflavones vary.

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Breast cancer: The research is mixed. Those who eat a high soy diet during adolescence may have a lower risk of breast cancer later in life, but some studies show that isoflavones from soy can increase the risk of cancer.  

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Type 2 diabetes: The research says that eating soy protein or fermented soy may reduce blood sugar in those with diabetes.

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Diarrhea in infants: Soy formula supplementation may shorten the duration of diarrhea (compared to drinking formula from cow’s milk). It’s important to note that in adults, soy fiber was NOT found to improve diarrhea.

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High cholesterol: Research strongly suggests that isoflavones from soy reduce bad cholesterol called LDL. Only protein-based food sources of isoflavones such as tofu or tempeh were found to lower cholesterol; isoflavone supplements were not effective. Red clover has also been found to have a cardiovascular benefit, raising HDL, or good cholesterol.

High blood pressure: Eating soy may lower the blood pressure slightly and is suggested for those with slight increases in blood pressure, but NOT in people with severely elevated blood pressure.

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Irritable bowel syndrome (IBS): Some research found that soy isoflavones may improve symptoms of IBS, such as abdominal pain.

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Menopausal symptoms: Symptoms such as irritability, depression, and hot flashes may be lessened with the use of isoflavones. However, isoflavones were NOT found to be beneficial for night sweats.

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Osteoporosis: In studies, soy protein from food sources and isoflavones in supplement form were both found to increase bone density.

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