Soy cuts hot flashes, night sweats of postmenopausal women
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A small, short-term, double-blind, Swedish study involving 60 healthy postmenopausal women finds that 60 mg isoflavones daily can reduce hot flashes and night sweats by about half without any negative effects on the endometrium, breasts, or lipid levels.
What are isoflavones? Isoflavones belong to a class of compounds known as flavonoids. Products made from them include soya flour, soya milk, tempeh and tofu. They are present in varying amounts, depending on the type of soya product and how it is processed. Isoflavones are also found in dietary supplements, most of which are based on soya, but some come from other plant sources, such as red clover.
The principal isoflavones in the soya bean are genistein, daidzein and glycetin. These are usually found in the form of glycosides, which after ingestion are hydrolysed in the large intestine by the action of bacteria to release isoflavones.
What do they do? By virtue of their chemical structure, isoflavones are weak estrogens and are also known as phytoestrogens. They are capable of binding to estrogen receptors, where, depending on the hormonal status of the individual, they seem to exert either estrogenic or antiestrogenic effects. This has led to speculation that, premenopausally, isoflavones may be antiestrogenic, whereas postmenopausally they could act as estrogen receptor agonists.
In the Swedish study, researchers gave participants a soybean-based fruit drink containing 60 mg isoflavones or placebo daily for 3 months.
They found that in the women receiving the isoflavones, hot flashes and night sweats were reduced by 57% and 43%, respectively, without changes in levels of circulating estradiol or follicle-stimulating hormone and without affecting expression levels of steroid receptors; estrogen receptors α, β, and βcx; progesterone receptors A and B; or the proliferation marker Ki67.
Furthermore, the authors of the study observed no side effects on body weight, lipoprotein profiles, or endometrial thickness as measured by ultrasound.
The researchers concluded that while the findings are encouraging, the question of whether isoflavones can substitute for estrogen replacement requires further investigation.