Women fed soy-based formula as babies were more likely to have severe menstrual pain as adults.
Consuming soy-based formula during infancy may be linked to severe menstrual pain in adulthood, researchers report.
A study published in Human Reproduction included 1,553 African-American women ages 23 to 35 with information on soy formula feeding gathered by questionnaires. To determine menstrual pain, they asked women whether they had ever taken prescription or over-the-counter medication to prevent menstrual cramps or pelvic pain.
About 13 percent of the women reported being fed soy formula as babies. They were significantly more likely than those who had not been fed soy formulas to have used hormonal contraception for menstrual pain, especially in the first five years after menarche.
The precise mechanism is unknown, but soy contains phytoestrogens that have been shown in animal studies to affect uterine development and adult uterine function.
The study relied on the subjects’ recall, and there was no data on the reasons for formula feeding or on the feeding of solid foods during infancy. The lead author, Kristen Upson, a researcher at the National Institutes of Health, said the observational study shows an association, not cause and effect.
Still, she said, menstrual pain is common, and “our findings point to the need for a greater understanding of exposure, even those that occur earlier in life.”