An article published online on September 22, 2010 in the American Journal of Clinical Nutrition reports an association between multivitamin use and a reduced risk of myocardial infarction (MI or heart attack) in older women.

The current study included 2,262 women with a history of cardiovascular disease and 31,671 women with no history of the disease who participated in the Swedish Mammography Cohort established between 1987 and 1990. The participants completed a dietary questionnaire in 1997 which provided the Karolinska Institutet researchers with information concerning supplement use.

Over the 10.2 year average follow-up period, 269 heart attacks occurred among women who had cardiovascular disease, and 932 occurred in those with no history. Among women who had no history of the disease, those who reported using a multinutrient supplement had a 27 percent lower adjusted risk of heart attack than those who were not supplement users. Using a multivitamin along with other supplements was associated with a 30 percent lower risk, and use for at least five years was linked to a 41 percent lower risk of myocardial infarction compared to nonusers. Multivitamin use was not associated with a significant benefit in those with pre-existing disease.

Concerning the contradiction of the current study's findings in light of other research which failed to uncover a benefit, the authors explain that ingredients and dosage of the components of multinutrient supplements vary, that some trials were conducted in subjects with pre-existing cardiovascular disease, and that the majority of trials had short follow-up periods. They attribute the vitamins' protective benefit to their antioxidant properties, which retard atherosclerosis via free radical scavenging, and the ability of B vitamins to lower homocysteine levels. Minerals included in multinutrient supplements may also have cardioprotective effects, including the possibility of magnesium to inhibit insulin resistance, decrease vascular tone, and prevent pro-inflammatory changes and endothelial dysfunction, and the incorporation of selenium into protective antioxidant enzymes.