This Article Full Text Full Text (PDF) Submit a related Letter to the Editor Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Lu, L.-J. W. Articles by Nagamani, M. Search for Related Content PubMed PubMed Citation Articles by Lu, L.-J. W. Articles by Nagamani, M.

Effects of an Isoflavone-Free Soy Diet on Ovarian Hormones in Premenopausal Women¹

Departments of Preventive Medicine and Community Health (L.-J.W.L., K.E.A., J.J.G.) and Obstetrics and Gynecology (M.N.), The University of Texas Medical Branch, Galveston, Texas 77555

Address correspondence and requests for reprints to: Lee-Jane W. Lu, Ph.D., Department of Preventive Medicine and Community Health, The University of Texas Medical Branch, 700 Harborside Drive, Galveston, Texas 77555-1109. E-mail: LLu{at}UTMB.EDU

Abstract

Soy intakes have been associated with reduced rates of breast cancer in some Asian populations. The isoflavones daidzein and genistein and other components of soybeans may modulate endocrine function and lead to beneficial health effects. This study determined the effects of a soy diet containing minimum amounts of isoflavones on circulating levels of ovarian hormones and gonadotropins. Nine healthy, regularly cycling women consumed a constant soya-containing diet on a metabolic unit starting on day 2 of a menstrual cycle until day 2 of the next cycle. The soy diet was calculated to maintain constant body weight and included a 36-oz portion of soymilk that provided 334 kilocalories and less than 5 mg/day of total isoflavones. The energy distribution of the soy diet was 35.9% fat, 14.0% protein, and 49.8% carbohydrate whereas the home diets averaged 39% fat, 16.6% protein, and 42.5% carbohydrate. For the group, the soya diet provided more carbohydrate (P = 0.002) and less protein (P = 0.005) than the home diets. Daily consumption of the soya diet reduced daily circulating levels of 17ß-estradiol over the entire menstrual cycle by 20% (P < 0.01, paired t test, two-tailed) and progesterone by 33% (P < 0.0001) compared with levels during the home diet period, but had no effect on LH, FSH, or sex hormone-binding globulin. The decreases in follicular phase 17ß-estradiol during the soy diet can be accounted for by changes in energy intakes, nutrient density, and fiber intake, whereas changes in luteal phase 17ß-estradiol were most strongly associated with differences in fiber intake. Changes in progesterone levels were most strongly associated with changes in protein intake and much less with other nutrients. Isoflavones were not detectable in plasma and urine during either the soy or home diet periods. These results suggest that at least under the conditions of this study, a soy diet with low levels of isoflavones and low energy intake from protein can reduce circulating ovarian steroids without altering gonadotropins. Our results are consistent with previous studies showing decreased ovarian hormone levels and decreased risk of breast cancer in populations consuming soya diets and an inverse relationship between animal protein intake and breast cancer risk and, therefore, may have implications for breast cancer prevention.

This article has been cited by other articles:

				K. Jaceldo-Siegl, G. E Fraser, J. Chan, A. Franke, and J. Sabate Validation of soy protein estimates from a food-frequency questionnaire with repeated 24-h recalls and isoflavonoid excretion in overnight urine in a Western population with a wide range of soy intakes Am. J. Clinical Nutrition, May 1, 2008; 87(5): 1422 - 1427. [Abstract] [Full Text] [PDF]

				M. Cotterchio, B. A. Boucher, M. Manno, S. Gallinger, A. Okey, and P. Harper Dietary Phytoestrogen Intake Is Associated with Reduced Colorectal Cancer Risk J. Nutr., December 1, 2006; 136(12): 3046 - 3053. [Abstract] [Full Text] [PDF]

				A. A Franke, B. M Halm, L. J Custer, Y. Tatsumura, and S. Hebshi Isoflavones in breastfed infants after mothers consume soy. Am. J. Clinical Nutrition, August 1, 2006; 84(2): 406 - 413. [Abstract] [Full Text] [PDF]

				I. Woclawek-Potocka, M. M. Bah, A. Korzekwa, M. K. Piskula, W. Wiczkowski, A. Depta, and D. J. Skarzynski Soybean-Derived Phytoestrogens Regulate Prostaglandin Secretion in Endometrium During Cattle Estrous Cycle and Early Pregnancy Experimental Biology and Medicine, March 1, 2005; 230(3): 189 - 199. [Abstract] [Full Text] [PDF]

				G. Maskarinec, A. A. Franke, A. E. Williams, S. Hebshi, C. Oshiro, S. Murphy, and F. Z. Stanczyk Effects of a 2-Year Randomized Soy Intervention on Sex Hormone Levels in Premenopausal Women Cancer Epidemiol. Biomarkers Prev., November 1, 2004; 13(11): 1736 - 1744. [Abstract] [Full Text] [PDF]

				U. A. Kayisli, C. A. H. Aksu, M. Berkkanoglu, and A. Arici Estrogenicity of Isoflavones on Human Endometrial Stromal and Glandular Cells J. Clin. Endocrinol. Metab., December 1, 2002; 87(12): 5539 - 5544. [Abstract] [Full Text] [PDF]

				L. Hilakivi-Clarke, E. Cho, A. Cabanes, S. DeAssis, S. Olivo, W. Helferich, M. E. Lippman, and R. Clarke Dietary Modulation of Pregnancy Estrogen Levels and Breast Cancer Risk among Female Rat Offspring Clin. Cancer Res., November 1, 2002; 8(11): 3601 - 3610. [Abstract] [Full Text] [PDF]

				M. S. Kurzer Hormonal Effects of Soy in Premenopausal Women and Men J. Nutr., March 1, 2002; 132(3): 570S - 573. [Abstract] [Full Text] [PDF]

				C. A. Lamartiniere, J. Wang, M. Smith-Johnson, and I.-E. Eltoum Daidzein: Bioavailability, Potential for Reproductive Toxicity, and Breast Cancer Chemoprevention in Female Rats Toxicol. Sci., February 1, 2002; 65(2): 228 - 238. [Abstract] [Full Text] [PDF]