Soy May Improve Cognitive Function in Early Menopause

Emma Hitt, PhD

June 30, 2011

June 30, 2011 — In menopausal women, soy and soy isoflavones appear to benefit cognitive function in women younger than 65 years, but may have little benefit for women older than 65 years, according to a working group of faculty and panelists who convened to review the subject.

Thomas B. Clarkson, DVM, professor of comparative medicine at Wake Forest School of Medicine in Winston-Salem, North Carolina, and Wulf H. Utian, MD, PhD, DSc(Med), NCMP, executive director emeritus and honorary trustee of the North American Menopause Society, cochaired the committee. The report was published in the July issue of Menopause.

The North American Menopause Society/Utian Translational Science Symposium on Soy and Soy Isoflavones took place October 9 and 10, 2010, in Chicago, Illinois. The round table included 22 clinicians and experts who attended presentations and then separated into specialty groups to discuss the latest evidence-based research.

The workshop, entitled "Basic and Clinical Considerations of the Peri- and Postmenopausal Effects of Soy, Soy Isoflavones, and Their Metabolites, Including S(-) Equol," included evidence-based presentations on various topics, including "the prevalence of use of soy and soy isoflavones; the molecular, cellular, and physiologic effects of isoflavones; and the effects of soy and soy isoflavones on menopausal symptoms, breast and endometrial cancer, atherosclerosis, bone loss, and cognition."

"From the hundreds of studies reviewed in this report, there are mixed results of the effects on midlife women," the authors write. "Soy-based isoflavones are modestly effective in relieving menopausal symptoms," they add.

US Soy Consumption on the Rise

According to the researchers, US dietary consumption of soy has increased several-fold during the past 15 years, with one third of Americans consuming soy food or beverages at least once a month.

"Despite this increase, dietary consumption of soy in the United States remains far below that in Asia," they write. Although the current prevalence of supplement use is unknown, nearly 1 in 10 US adults reported use of soy supplements in a 2002 nationwide survey.

Supplements for Menopausal Symptom Effects

The authors recommend that women experiencing symptoms of menopause may benefit from a starting dose of 50 mg/day of isoflavones, given for at least 12 weeks. In responding women, treatment can be continued while monitoring for adverse effects.

Some women may not have adequate intestinal equol generation from isoflavone intake, and therefore may not experience improvement in menopausal symptoms. "A supplement containing natural S(-)-equol may be effective for some women who do not have the capacity to produce equol," the authors note. Soy-based isoflavones were modestly effective in relieving menopausal symptoms, with supplements providing higher proportions of genistein or S(-)-equol providing more benefits.

Cancer, Bone and Cardiovascular Effects Unclear

Soy food consumption was associated with lower risk for breast and endometrial cancer in observational studies. However, the effects of isoflavones on the breast and uterus present a "complex" picture, with some conflicting experimental findings.

"The efficacy of isoflavones on bone has not been proven, and the clinical picture of whether soy has cardiovascular benefits is still evolving," the note.

According to the authors, no compelling evidence exists for a beneficial effect of soy isoflavones on bone density in postmenopausal women; therefore, "more human studies need to be conducted with equol producers, with soy products with a higher genistein content, and with higher doses of isoflavones (>120 mg/day)."

The researchers also point out that with respect to cardiovascular system effects, clinical studies are needed to determine whether soy and soy isoflavones have plasma lipid-independent benefits on cardiovascular health, particularly in perimenopausal and recently postmenopausal women.

Critical Window for Soy Benefits in Younger Women

Cognitive benefit from isoflavone therapy may follow a "critical window" hypothesis similar to that observed with hormone therapy, in which younger postmenopausal women derive more benefit than older women. Clinical trials indicate that soy and soy isoflavones have some benefit on cognitive function in women younger than 65 years, with little benefit for women older than 65 years.

"Larger studies are needed for definitive support, particularly in younger postmenopausal women," the authors conclude. "The ongoing [Women's Isoflavone Soy Health] trial will provide important new insights into the effects of soy on cognition from a sample of about 300 healthy postmenopausal women randomly allocated to 25 g/day of isoflavone-rich soy protein versus milk protein placebo."

This study was supported by unrestricted grants from Otsuka Pharmaceutical, Pharmavite LLC, and the Allmen Foundation. Faculty and panelists that contributed to this article have disclosed various financial relationships, including serving as advisory board members and consultants and receiving grant research support from the following companies and institutions: Teva, Pfizer, Otsuka, Solea, Bayer Schering, Archer Daniels Midland, Pharmavite, United Soybean Board, WhiteWave Foods, Sanitarium Health Foods, Bene Therapeutics, Bionovo, Cleveland Clinics Foundation Innovations Center, Hygeia, Lupin, Merck, Novogyne, Cadbury, GTC Bioherapeutics, Sara Lee, DMI, Friesland Campina, General Mills, and Tate and Lyle.

Obstet Gynecol. 2011;18:732-753. Abstract

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