Soy is often used to support the vaginal system, particularly for women experiencing symptoms related to menopause, such as vaginal dryness and atrophy. The scientific rationale is primarily based on the presence of isoflavones in soy, which are phytoestrogens—plant compounds with estrogen-like activity. During menopause, declining estrogen levels can lead to changes in the vaginal tissue, resulting in dryness, thinning, and discomfort.

Multiple randomized controlled trials and meta-analyses have investigated the effects of soy isoflavones on menopausal symptoms, including those affecting the vagina. Some clinical studies suggest that soy isoflavone supplementation can modestly improve vaginal cytology (the health of vaginal cells) and reduce symptoms of dryness and discomfort, although the magnitude of the effect is generally less than that seen with hormone replacement therapy. Not all studies are positive, and results are somewhat mixed, but there is a biological plausibility and enough supportive evidence to warrant a moderate rating.

Traditional use of soy in Asian cultures has not specifically focused on vaginal health, but the lower incidence of menopausal symptoms in populations with high dietary soy intake has contributed to interest in its use. Overall, scientific evidence exists, but it is not definitive, and soy is best considered as a mild, natural support rather than a primary treatment.