Women who consume more iron from plant-based sources could be less likely to feel pre-menstrual symptoms like bloating and depression than those having less of the nutrient, a U.S. study suggests.

With data from the Nurses Health Study II on diet and lifestyle, researchers at the University of Massachusetts Amherst assessed the mineral intake of about 3,000 women aged 25 to 42 using food questionnaires. None of the women had PMS at the outset and 1,057 women were diagnosed with it over the 10-year study period.

Vegetables such as peas and spinach contain nonheme iron. A diet rich in the mineral may help protect against PMS. (Nguyen Huy Kham/Reuters)

Previous research suggests that PMS affects an estimated 8 per cent to 15 per cent of women during their reproductive years, leading to symptoms such as breast tenderness, abdominal bloating, appetite changes, depression and anxiety that can interfere with regular activities.

"The present study suggests that high intakes of nonheme iron and perhaps zinc may be associated with a lower risk of PMS, whereas a high potassium intake may be associated with a higher risk," the study's senior author Elizabeth Bertone-Johnson and her co-authors concluded in Tuesday's online issue of the American Journal of Epidemiology. Nonheme iron is iron from certain vegetables or supplements but not meat.

Bertone-Johnson suggested that women consume a balanced diet. Health Canada's list of foods containing nonheme iron includes legumes such as bean and lentils, cereal, nuts and seeds.

Iron may be related to PMS because it is involved in producing serotonin, a neurotransmitter that helps to regulate mood, the researchers said.

They said they aren't aware of any previous studies looking at how iron intake may relate to PMS but that low iron levels have been associated with higher risk of postpartum depression.

In the study, risk of developing PMS was lowest in women who consumed more than 20 milligrams of iron daily. The researchers said a serving of iron-fortified cereal provides this level but it may otherwise be difficult to reach the level from food alone.

Keep minerals balanced

The recommended dietary allowance for women aged 19 to 49 who are not pregnant is 18 milligrams per day.

The heme iron from red meat and poultry did not show the same effect. Other minerals also seemed to have no effect.

High iron and zinc intake can be harmful, Bertone-Johnson cautioned.

"PMS is probably multifactorial, and it's probably way more complicated than one or two supplements or mineral deficiencies might cause," Dr. Fredric Moon, medical director of general obstetrics and gynecology at Winthrop University Hospital in Mineola, N.Y., told Health Day News.

The study relied on participants to self report their food and supplement intakes. Women also had to recall menstrual symptoms from previous years in combination with clinical diagnosis of PMS.

The findings were only in women aged 25 and may not apply to those who develop PMS in adolescence or early adulthood who weren't studied.

The researchers considered factors such as calcium intake, age, smoking, weight, pregnancy history and use of oral contraceptives in their analysis. The study does not prove any cause and effect relationships.

The study was funded by grants from GlaxoSmithKline Consumer Healthcare, Rexall/Cellasene settlement litigation and the U.S. National Cancer Institute.