LWWJ406-08 December 22, 2007 11:20 Char Count= 0 Top Clin Nutr Vol. 23, No. 1, pp. 13–22 Copyright c  2008 Wolters Kluwer Health | Lippincott Williams & Wilkins DIETETIC RESEARCH PROJECTS Effects of Dietary and Supplemental Forms of Isoflavones on Thyroid Function in Healthy Postmenopausal Women Tracy Ryan-Borchers, PhD, RD; Boon Chew, PhD; Jean Soon Park, PhD; Michelle McGuire, PhD; Lisa Fournier, PhD; Kathy Beerman, PhD Because of the health concerns associated with hormone replacement therapy, many women are seeking alternative therapies. Compounds such as soy isoflavones appear to reduce the risk of some age-related diseases and to lessen the severity of menopausal symptoms. However, concerns regarding harmful effects of soy isoflavones on thyroid function have been reported. This 16- week, double-blinded, placebo-controlled trial evaluated the effects of soy isoflavones on thyroid- stimulating hormone in healthy postmenopausal women. The results of this study suggest that isoflavones obtained from either soymilk or supplements have no effect on thyroid-stimulating hormone in well-nourished postmenopausal women. Key words: menopause, soy isoflavones, thyroid function M ENOPAUSE, defined as the cessation of menstruation resulting from the loss of ovarian follicular activity, is associated with in- creased risk of several age-related diseases, in- cluding coronary heart disease and osteoporo- Author Affiliations: Department of Nutrition, Oregon Health Science University, Portland, Oregon (Dr Ryan-Borchers); and Departments of Food Science and Human Nutrition (Drs Chew, Park, McGuire, and Beerman) and Psychology (Dr Fournier), Washington State University, Pullman. Funding for this study was provided, in part, by a grant from the Washington State Attorney General Office. The authors express their appreciation to the study partici- pants for all their hard work. We all extend gratitude to White Wave, Inc, and Archer Daniel Midland for their contributions to the study. Corresponding author: Kathy Beerman, PhD, Depart- ment of Food Science and Human Nutrition, Washing- ton State University, Pullman, WA 99164 (beerman@ wsu.edu). sis. Furthermore, symptoms such as night sweats, hot flashes, and mood swings often ac- company the early stages of menopause. Many women rely on standard hormone replace- ment therapy (HRT) to reduce menopausal symptoms and associated health risks. How- ever, there is growing evidence that HRT can increase the risk of developing venous thrombosis, cardiovascular disease, and cer- tain cancers. 1–4 These studies, which include the Women’s Health Initiative, the largest ran- domized clinical trial conducted to assess long-term use of combined estrogen-progestin HRT, have raised important issues concern- ing health risks associated with HRT. 5–8 Thus, a growing number of women are seeking al- ternative therapies to alleviate menopausal symptoms most notably soy. 9,10 In recent years, health benefits associated with consumption of soybeans have been widely publicized. Some studies have found 13