Soy Isoflavones Show Promise for Postmenopausal Sexual Health

A recent meta-analysis of randomized controlled trials suggests that soy isoflavones, found in foods like tofu and tempeh, could moderately alleviate sexual and urogenital symptoms experienced by postmenopausal women.

Effects of Soy Isoflavones on Menopausal Symptoms

The study, published in the International Journal of Impotence Research, reviewed 13 randomized controlled trials involving 1,325 postmenopausal women globally. Participants consumed soy isoflavones through diet or supplements at doses ranging from 40 to 160 milligrams daily over periods of four to 24 weeks.

Researchers assessed menopausal symptoms via questionnaires covering physical and emotional experiences, including vaginal dryness, urinary issues, hot flashes, and mood changes. The analysis revealed improvements in vaginal dryness and urogenital symptoms such as painful urination, urinary urgency, decreased arousal, and pelvic discomfort.

However, soy isoflavones did not show significant benefits for painful intercourse, hot flashes, night sweats, or psychological symptoms. The authors noted the need for longer-term studies and highlighted limitations such as small sample sizes and reliance on self-reported data.

Understanding Soy Isoflavones and Their Role

Soy isoflavones are phytoestrogens naturally present in soy products like soybeans, tofu, and tempeh. Their chemical structure resembles estrogen, allowing them to weakly bind to estrogen receptors in the body, according to Heather Bartos, MD, FACOG, a menopause specialist at plusOne Wellness Collective.

Despite this, Bartos emphasized that soy isoflavones are not equivalent to hormone replacement therapy (HRT). “They don’t actually replace estrogen, but they may create a mild estrogen-like effect in certain tissues affected by menopause, particularly vaginal and urinary tissues,” she explained. In contrast, HRT involves tailored hormone doses as a stronger medical intervention.

Dietary Sources and Supplementation Considerations

Melissa Groves Azzaro, RDN, LD, a registered dietitian specializing in nutrition and hormones, noted that soy isoflavones might be better absorbed from food than supplements, citing 2009 research on the bioavailability of genistein and daidzein. However, supplements often contain higher doses, complicating direct comparisons.

Achieving effective soy isoflavone intake through diet requires consuming two to three soy-containing meals daily, said Stacey Silverman Fine, MD, FACOG, MSCP, an OB-GYN at Maven Clinic in New York. She described this as a significant dietary change for many American women but feasible with planning.

Groves Azzaro recommends starting with one to two servings of soy foods per day while monitoring symptoms. Combining supplements with dietary sources is also an option.

Examples of Soy Isoflavone Content in Foods

Registered dietitian Jamie Mok, MS, RD, RYT, provided examples of soy isoflavone content in common soy foods:

• Half a cup of cooked soybeans: 47 milligrams
• 3 ounces of tempeh: 37 milligrams
• 1 cup of soy milk: 30 milligrams
• 3 ounces of firm tofu: 20 milligrams
• 1 tablespoon of miso: 7 milligrams

Who May Benefit and Precautions

Bartos indicated that soy isoflavones may offer meaningful relief for women experiencing mild to moderate vaginal dryness and urogenital symptoms, especially those seeking non-hormonal options or who have medical contraindications to HRT, such as histories of blood clots, cardiovascular disease, or certain cancers.

Conversely, Groves Azzaro advised consulting a healthcare provider before starting soy isoflavone supplementation if one is taking medications that interact with soy, has a history of estrogen-positive cancer, is currently on hormone replacement therapy, or uses estrogen-blocking drugs like Tamoxifen.

While soy isoflavones are unlikely to fully address severe menopausal symptoms alone, they may be a valuable part of symptom management for some postmenopausal women, according to the experts involved.