Infant milk formula in childhood linked to dysmenorrhoea later

Women who were fed soy formula as infants are more likely to experience severe menstrual pain in their early adulthood than unexposed women suggests a new research published in the journal Human Reproduction.

The observation adds to the growing body of literature suggesting that early life exposure to soy formula may have detrimental effects on the reproductive system.

Kristen Upson, National Institute of Environmental Health Sciences, National Institutes of Health, NC, USA, and colleagues conducted the study to determine whether soy formula feeding during infancy associated with menstrual pain in reproductive-age women.

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Menstrual pain (dysmenorrhea) is characterized by menstrual bleeding-related abdominal pain, cramping or a backache. It is considered the most common menstrual complaint, with population-based studies reporting a prevalence of 60% among reproductive-age women. It can have a substantial impact on the quality of life, work productivity and relationships.

For the study, the researchers examined data from 1,553 African-American women, aged 23-35, participating in the NIEHS Study of Environment, Lifestyle, and Fibroids (SELF).

Data on infant soy formula feeding was ascertained by a self-administered questionnaire for 1553 participants, with 89% of participants receiving assistance from their mothers.

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Key Findings:

• Women fed soy formula as infants were 20% more likely than unexposed women to use medication for menstrual pain within five years of menarche.


• Soy formula feeding was associated with a 40% increased risk of ever use of hormonal contraception for menstrual pain; the magnitude of the association was stronger if hormonal contraception (if ever used for menstrual pain) was first used within 5 years of menarche.


• Soy formula feeding was also associated with current use of hormonal contraception (if ever used for menstrual pain), although the confidence interval included the null.


• Among participants who reported having menstrual periods and not using hormonal birth control all the time when ages 18–22 years (n = 1277), women fed soy formula as infants were 50% more likely than unexposed women to report experiencing moderate or severe menstrual pain with ‘most periods’, although no association was observed with ‘every period.'

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 prematurely. For full-term infants, the AAP recommends soy formula in rare cases where the child's body cannot break down the sugars in milk or if the family prefers a vegetarian diet.

Upson said some estimates put the prevalence of menstrual pain in women of reproductive age at 60 percent. She added that menstrual pain can have a substantial impact on the quality of life, affecting school performance, work productivity, and relationships.

"Given how common menstrual pain is and the impact it can have on women's lives, the next steps in research should examine exposures, even those that occur earlier in life that may increase a woman's risk of experiencing menstrual pain," said Upson.

"In conclusion, our data suggest that soy formula feeding during infancy is associated with menstrual pain in adulthood. Our observation adds to the growing body of literature suggesting that early life exposure to soy formula may have detrimental effects on the reproductive system," write the authors.