Soy and menopausal health, breast cancer prevention

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Soy has recently been reviewed and supported for introduction into general medical practice as a treatment for distressing vasomotor symptoms of menopause, such as hot flashes, but its use in other medical areas, such as heart health, requires further research, according to a new report reviewing the risks and benefits of soy protein, isoflavones and metabolites in menopausal health from The North American Menopause Society (NAMS)/Wulf H. Utian Translational Science Symposium, published in the July Menopause, the peer-reviewed NAMS journal.

"Although a significant amount of scientific research about soy and soy isoflavones exists, the adoption of soy isoflavones into the care of women in menopause has to date been recommended mainly by physicians and health care practitioners involved in integrative medicine. We believed that facilitating a robust review of the current scientific evidence about the benefits and risks of soy could yield a document useful to physicians to help them make decisions about soy use with their patients, particularly those in menopause," said Belinda H. Jenks, Ph.D., director of Scientific Affairs & Nutrition Education at Pharmavite LLC. Otsuka Pharmaceutical Co., Ltd., Pharmavite LLC and the Allmen Foundation supported the development of the symposium and report via an unrestricted educational grant.

The report focuses on a review of soy's mechanism of action and processing within the body (bioavailability and pharmacokinetics), as well as on several therapeutic areas, concluding that use of soy isoflavones for hot flashes is reasonable and that soy food consumption is associated with lower risk of breast and endometrial cancer. The report also recommended more research to further characterize the effects of soy isoflavones on bone and cardiovascular health as well as cognition, which involves thinking, reasoning, or remembering.

The report, approved by the NAMS Board of Trustees, was authored by 22 clinicians and well-respected scientific research experts in women's health and botanicals who participated in the symposium in October 2010. They examined basic and clinical research findings from more than two hundred key published controlled trials as well as laboratory studies of the soy isoflavones genistein and daidzein and the daidzein metabolite, S-equol.

Soy-isoflavones Reasonable for Menopausal Symptoms

The NAMS report advises that in postmenopausal women with distressing vasomotor symptoms, such as hot flashes, initial treatment with soy isoflavones is reasonable because of demonstrated modest effectiveness in early post-menopausal women who have at least four hot flashes daily. The report recommends a starting dose of 50 milligrams (mg) or more daily for at least 12 weeks. If a woman responds, the treatment can continue with monitoring for side effects, but for women who do not respond after 12 weeks, other treatment options should be discussed, the authors suggest.

The authors' menopause symptom treatment recommendations were based on a review of 14 studies that included data on soy isoflavone content and dosing, at least 12 weeks of treatment, women who experienced natural (not induced) menopause and the women's average age, their prevalence of hot flashes at study start and their magnitude of symptom improvement.

Potential Protection for Breast and Endometrial Cancer

Soy foods, in populations that typically consume them, appear to protect against breast cancer. Therefore, the NAMS report advises that moderate life-long dietary soy consumption is recommended as part of a healthy lifestyle. The best evidence indicates that there are no adverse effects from this diet and it has potential for prevention of breast and endometrial cancer, the report states.

However, the authors note that specific recommendations regarding soy food or soy isoflavone consumption by breast cancer survivors cannot be made at this time, although such studies in humans indicate either no effect or a protective effect, but in contrast laboratory and rodent studies indicate a potential for risk.

The authors recommend studies of endometrial risk should focus on long-term, postmenopausal exposures to soy. The authors' breast and endometrial cancer recommendations were based on a review of at least 18 studies.