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Soy formula feeding in infancy may increase menstrual pain in adulthood
Soy formula feeding during infancy is associated with several indicators of severe menstrual pain in reproductive-aged women, including a 50% increased risk for moderate to severe menstrual discomfort with most periods during early adulthood, according to findings published in Human Reproduction.
“Exposures — even those that occur earlier in life — may increase a women’s risk of experiencing menstrual pain,” Kristen Upson, PhD, MPH, a postdoctoral fellow in the epidemiology branch at the National Institute of Environmental Health Sciences (NIEHS) at the NIH, told Endocrine Today. “Our research highlights the prevalence of menstrual pain and that exposure to estrogens during infant development, such as the phytoestrogens in soy formula, may affect reproductive health in adulthood.”
Upson and colleagues analyzed data from 1,553 black women aged 23 to 35 years at enrollment, participating in the Study of Environment, Lifestyle and Fibroids. Data on infant soy formula feeding was assessed by questionnaire and information on menstrual pain indicators was assessed via web and telephone interviews. Researchers used log-binomial regression or log-multinomial regression models to assess RR for menstrual pain with exposure to soy formula.
The researchers found that women who were ever fed soy formula as infants were 40% more likely vs. unexposed women to report ever use of hormonal contraceptives for menstrual pain (RR = 1.4; 95% CI, 1.1-1.9), as well as 50% more likely to report moderate to severe menstrual discomfort or pain with “most periods” during early adulthood (RR = 1.5; 95% CI, 1.1-2).
In sensitivity analyses that excluded 111 participants fed soy formula for less than 4 months or first fed soy formula after age 2 months and restricting the study population to those whose mother assisted with the questionnaire, researchers reported a stronger association between ever and current use of hormonal contraceptives for menstrual pain, the frequency of moderate to severe menstrual pain and soy formula feeding. Results persisted after adjusting for household income during a participant’s childhood and being ever breastfed as an infant.
“Although a growing body of research studies collectively lend support to the potential reproductive health consequences of early-life exposure to soy formula, our observational study is not sufficient for changing infant feeding recommendations,” Donna Baird, PhD, a senior investigator in the epidemiology branch at NIEHS and leader of the Women’s Health Group, told Endocrine Today. “The American Academy of Pediatrics (AAP) promotes human milk as the ideal source of nutrition for infants. It does not recommend soy formula for babies born premature. For full-term infants, the AAP recommends soy formula in rare cases where the infant’s body cannot break down the sugars in milk (galactosemia and hereditary lactase deficiency) or if the family prefers a vegetarian diet.”
Baird said menstrual pain can have a substantial effect on the quality of life, affecting school performance, work productivity and relationships.
“The additional study of factors which may increase a women’s risk of experiencing menstrual pain is warranted to inform prevention efforts and improve women’s health,” she said. – by Regina Schaffer
For more information:
Kristen Upson, PhD, M P H, can be reached at the Epidemiology Branch, NIEHS, NIH, 111 TW Alexander Drive, Rall Building 101, MD A3-05 NIEHS, Research Triangle Park, NC 27709; email: Kristen.upson@nih.gov.
Disclosure: The Intramural Research Program of the NIH, the NIEHS, the National Institute of Nursing Research and funds allocated for health research by the American Recovery and Reinvestment Act funded this study.