(Reuters) - Women who get a little more than the recommended daily amount of iron in their diets may be less likely to get a more severe form of premenstrual syndrome (PMS), according to a U.S. study.
Researchers writing in the American Journal of Epidemiology followed about 3,000 women over 10 years and found that those who consumed more than 20 milligrams (mg) per day of iron sources were 30 to 40 percent less likely to develop PMS than women who got less of the mineral.
"Most previous studies of PMS have focused on effective treatments and factors that differ between women who have PMS and those who don't," said lead author Elizabeth Bertone-Johnson, from the University of Massachusetts in Amherst.
"We were interested in looking further at some specific minerals," she added, noting that her team had previously studied the relationship between vitamin intake and PMS.
For the study, the researchers limited their analysis to PMS in which symptoms such as breast tenderness, bloating, depression and anxiety are so severe they "substantially impact life activities and social relationships."
That type of PMS affects between 8 percent and 15 percent of U.S. women, they wrote.
The study was based on data from a large ongoing study of U.S. nurses, who were between the ages of 25 and 42 years old in 1989, and it focuses on 3,025 women who did not have PMS in 1991.
Each woman completed three food questionnaires sent to them over the next 10 years, which asked how often they were eating 131 different types of foods and supplements. The researchers then compared the diets of the 1,057 women who went on to develop severe PMS during the study period to the diets of the 1,968 women who did not.
Overall, eating a diet that provided about 22 mg of iron every day was linked to a 33 percent decrease in a woman's risk of developing PMS during those 10 years, compared to the women who ate the least amount of iron - about 10 mg. The recommendations are 18 mg of iron per day.
Even greater iron consumption was tied to an even larger drop in risk for PMS, but some of the women were eating diets with too much of the mineral.
"I think our message - based on these data - is meeting the (recommended daily amount) for iron seems to have a significantly lower risk of PMS," said Bertone-Johnson. "We don't want to recommend women take the upper limit (of 42 mg) because of potential adverse consequences."
Women in the study with the highest iron intakes tended to get most of the mineral from non-meat sources.
The U.S. Institute of Medicine, which sets recommended dietary allowances for nutrients, points out that iron consumed from meat and poultry sources is more easily processed in the body, and that people who get their ion only from a vegetarian diet might want to consume as much as twice the recommended amount.
Bertone-Johnson said that while the research can't prove iron prevents PMS, they suspect the mineral may have something to do with the production of serotonin, a molecule that plays a role in many processes in the body and in the brain. Iron is necessary for the body to manufacture serotonin, they write.
"Our advice from this study is pretty similar to what we've taken from previous work... Not focusing on any one nutrient per se, just make sure your diet is balanced and you're meeting the '(recommended daily amount) on your own vitamins," Bertone-Johnson said. SOURCE: bit.ly/Y3YBE9
(Reporting from New York by Andrew Seaman at Reuters Health; editing by Elaine Lies)