Soy-Based Infant Formula Feeding and Menstrual Characteristics

Abstract

Soy-Based Infant Formula Feeding and Menstrual CharacteristicsAbstract Number:2526 Kristen Upson*, Quaker Harmon, Shannon Laughlin-Tommaso, and Donna Baird Kristen Upson* National Institute of Environmental Health Sciences, National Institutes of Health, United States, E-mail Address: [email protected] Search for more papers by this author , Quaker Harmon National Institute of Environmental Health Sciences, National Institutes of Health, United States, E-mail Address: [email protected] Search for more papers by this author , Shannon Laughlin-Tommaso Mayo Clinic, Departments of Obstetrics/Gynecology and Surgery, United States, E-mail Address: [email protected] Search for more papers by this author , and Donna Baird National Institute of Environmental Health Sciences, National Institutes of Health, United States, E-mail Address: [email protected] Search for more papers by this author AbstractBackground: Phytoestrogen exposure from soy formula feeding may disrupt reproductive system development during infancy, resulting in adverse outcomes in adulthood. A study of young adults who participated as infants in a clinical trial and were assigned to soy or cow-based formula feeding reported slightly longer menstrual bleeding duration and greater risk of menstrual discomfort with soy formula feeding. However, the authors did not observe an association with heavy menstrual flow or cycle length. Aim: We further investigated the relationship between infant soy formula feeding and menstrual characteristics, using several indicators of menstrual bleeding, pain, and cycle length.Methods: We used enrollment data from the Study of Environment, Lifestyle & Fibroids (SELF), a study of 1,696 African American women ages 23-34 years in Detroit, MI. Data on infant soy formula feeding (90% retrospectively reported by participant’s mother) and menstrual characteristics were available for 1,522 participants. Relative risk (RR) and 95% confidence intervals (CI) were estimated using log-binomial regression, adjusting for participant age.Results: Soy formula feeding during infancy was associated with several indicators of menstrual pain and heavy bleeding, including a 50% increased risk of ever use of a contraceptive method for menstrual pain (RR 1.5, 95% CI: 1.1-2.0) and a 30% increased risk of ever use of non-steroidal anti-inflammatory medications to treat heavy menstrual bleeding (RR 1.3, 95% CI: 1.0-1.6). We also observed an increased risk of shorter menstrual cycle length (=24 vs. 25-30 days) among women (n=937) who were not using hormonal contraception the year before last menstrual period (RR 1.4, 95% CI: 1.0-1.9). We did not observe an association with menstrual bleeding duration.Conclusions: Our observations suggest that soy-based infant formula feeding may alter postnatal reproductive system development, leading to adverse menstrual characteristics in women.