Plant compounds from soy germ with a structure similar to oestrogen.
Why it’s used: Traditionally used to support women through the menopause.
Soy isoflavones are natural plant compounds found in soya beans, with the highest concentration in the germ, the tiny part of the bean that would grow into a new plant. The main ones are genistein, daidzein and glycitein. Their structure is similar to oestrogen, which is why they are often called phytoestrogens.
People in East Asia have eaten soya foods such as tofu, miso and soya milk for centuries, so isoflavones are a familiar part of many diets. Supplements are different in that they concentrate isolated isoflavones from soy germ or soya bean extract. On a label you will usually see soy isoflavones or soya germ extract, with the total isoflavone content given in milligrams.
Soy isoflavones are traditionally used to support women through the menopause, and they are often paired with red clover, sage or black cohosh. Researchers have studied them in many trials looking at hot flushes and bone health after the menopause, with mixed findings. Soya is one of the 14 major allergens, so it is always highlighted on the label.
3 findings behind this ingredient. Hover a card for the detail and the source.
Systematic review of 19 double-blind randomised trials, 17 in meta-analyses, using a median 54 mg isoflavones for 6 weeks to 12 months. Products with more genistein were over twice as effective for frequency.
Meta-analysis of 10 randomised controlled trials with 608 women. Spine bone mineral density rose by 20.6 mg/cm² versus control, with larger gains above 90 mg a day or after 6 months.
Systematic review and meta-analysis of 12 studies in perimenopausal women. Isoflavones improved overall symptoms (Hedges' g -0.25) and depression (g -0.72), with no significant effect on hot flushes or sweating.
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EFSA reviewed the evidence in 2015 and found no indication of harm to the breast, womb or thyroid in post-menopausal women at the doses studied, up to 100 mg a day for up to 10 months. There was not enough data to judge safety for women with a history of hormone-sensitive cancer.
Not exactly. Soya foods such as tofu and soya milk contain isoflavones naturally, usually in smaller amounts. Supplements concentrate isolated isoflavones, which is why guidance on dose and duration applies to them.
Soy isoflavone supplements are mainly marketed to women in midlife, and the EFSA review focused on post-menopausal women. Soya foods are part of many healthy diets for everyone. If you are a man considering a concentrated supplement, talk it through with your GP or pharmacist.
Videos from doctors, research scientists and registered dietitians, for general education. They are independent of Nutra Formulations, do not refer to our products and are not medical advice for you.
Soy Phytoestrogens for Menopause Hot Flashes
Dr Michael Greger, MD, FACLM · NutritionFacts.org on YouTube
Information only, not medical advice. If you take medication, are pregnant or breastfeeding, speak to your GP or pharmacist first.
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