Soy Isoflavones

AvoidSuggested

2 studies · 2 recommendations

Last updated: February 25, 2026

Avoid1 studies

Soy isoflavones lack evidence for reducing hot flashes

Meta-analyses of randomized controlled trials found no reliable evidence that soy isoflavones are effective for treating hot flashes. Despite widespread use as a natural alternative, the clinical evidence does not support their efficacy for this indication.

Evidence

Which nonhormonal treatments are effective for hot flashes?

Authors: Kelsberg, Gary, Maragh, Leticia, Safranek, Sarah

Published: January 1, 2016

A clinical guideline based on systematic reviews and meta-analyses of RCTs (SOR: A) evaluated phytoestrogens including soy isoflavones for hot flash management. The evidence showed these compounds lack demonstrated effectiveness for reducing hot flash frequency or severity. For comparison, established nonhormonal pharmacologic treatments reduce hot flashes by approximately 25% (about one fewer per day), while estrogen reduces frequency by approximately 75% (2.5-3 fewer per day). Many of the RCTs evaluating phytoestrogens were noted to be low quality, further undermining confidence in any positive findings.

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Suggested1 studies

Soy isoflavone extracts may reduce hot flushes in postmenopausal women

This systematic review found that soybean isoflavone extracts may be effective in reducing hot flushes, whereas whole soybean foods, soybean-protein isolates, and red-clover extracts showed only limited evidence of efficacy for menopausal symptoms overall. The distinction between extract forms and whole-food forms is notable for symptom management.

Evidence

Critical review of health effects of soyabean phyto-oestrogens in post-menopausal women

Authors: Albertazzi, Paola, Atkins, Steve, Branca, Francesco, Cassidy, Aedin, Cross, Heide, Hall, Wendy, Manios, Yannis, Nielsen, Inge Lise, Steiner, Claudia, Tetens, Inge, Williamson, Gary, Wolk, Alicja

Published: August 2, 2017

Systematic review of placebo-controlled double-blind RCTs in healthy postmenopausal women evaluated multiple phyto-oestrogen sources including soybean-protein isolates, whole-soybean foods, extracts, supplements, and pure compounds containing primarily genistein and daidzein. Limited evidence supported soybean-protein isolates, whole-soybean foods, or red-clover (Trifolium pratense L.) extract for menopausal symptoms broadly. However, soybean isoflavone extracts specifically showed potential effectiveness for hot flush reduction. All isoflavone doses were standardized as aglycone equivalents to enable cross-study comparison. The review noted overall health benefits in postmenopausal women are subtle, with some well-designed studies failing to demonstrate protective effects.

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