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Bjarne K Jacobsen,1 Karen Jaceldo-Siegl,2 Synnøve F Knutsen,2 Jing Fan,2 Keiji Oda,2 Gary E Fraser2 1Department of Community Medicine, University of Tromsø, Tromsø, Norway; 2Department of Epidemiology, Biostatistics and Population Medicine, School of Public Health, Loma Linda University, Loma Linda, CA, USA Objectives: As little is known about the possible relationship between the intake of phytoestrogens and female fertility, we investigated the relationship between soy isoflavone intake and the risk of nulliparity and nulligravidity. Methods: A cross-sectional study of 11,688 North American Adventist women aged 30–50 years old with data regarding childbearing. These women were, as a group, characterized by a high proportion (54%) of vegetarians and a healthy lifestyle with a very low prevalence of smoking and alcohol use. Results: The mean isoflavone intake (17.9 mg per day) was very high compared to other Western populations. Only 6% of the women indicated no intake of isoflavones. We found, after adjustment for age, marital status, and educational level, an inverse relationship (P=0.05) between isoflavone intake and the likelihood of ever having become a mother. In women with high (≥40 mg/day) isoflavone intake (12% of this group of women), the adjusted lifetime probability of giving birth to a live child was reduced by approximately 3% (95% CI:0, 7) compared to women with low ( |
