The first ever study to evaluate whether dietary mineral intake is associated with PMS development has found that women who consume a lot of iron are between 30% and 40% more less likely to develop pre-menstrual syndrome (PMS) than women who consume lower levels.
Led by researchers at the University of Massachusetts Amherst and Harvard, the study assessed the mineral intake of around 3,000 women and followed them over a ten year study period.
"We found that women who consumed the most non-heme iron, the form found primarily in plant foods and in supplements, had a 30 to 40 percent lower risk of developing PMS than women who consumed the lowest amount of non-heme iron," said Dr Elizabeth Bertone-Johnson, who led the study.
"The level of iron intake at which we saw a lower risk of PMS, roughly greater than 20 mg per day, is higher than the current recommended daily allowance (RDA) for iron for premenopausal women, which is 18 mg per day," she added.
Writing in the American Journal of Epidemiology, Bertone-Johnson and her colleagues analysed data from approximately 3,000 women in a case-control study nested within the prospective Nurses' Health Study II. Women taking part in the study completed three food frequency questionnaires over the 10-year study period.
All of the women were free from PMS at baseline. After 10 years, 1,057 women were diagnosed with PMS and 1,968 remained free from PMS.
After adjusting for calcium intake and other factors, the researchers compared previous mineral intake reported by the women diagnosed with PMS with that of women who had few or no menstrual symptoms.
They found that women in the highest intake group for non-heme iron had a relative risk of PMS of 0.60 compared to women in the lowest intake group.
"We also saw some indication that high intake of zinc was associated with lower risk,” added Bertone-Johnson.
“In contrast, we were somewhat surprised to find that women consuming the highest amount of potassium had a higher risk of being diagnosed with PMS than women consuming the lowest amount of potassium.”
The unexpected finding of higher PMS risk with high potassium intake, even at levels below current recommendations of 4,700 mg per day, may be related to potassium's role in regulating fluid balance in the body, suggests the researchers.
“In general, results for mineral from food sources and minerals from supplements were similar,” she said – adding that the study findings now need to be replicated in other research.
“However, women at risk for PMS should make sure they are meeting the RDA for non-heme iron and zinc,” said Bertone-Johnson.
"The level of zinc intake at which we saw suggestion of a lower risk of PMS, greater than 15 mg per day, was also higher than current recommendations of 8 mg per day.”