Magnesium helps the heart maintain its normal rhythm. Doctors in one study measured the diets of 88,375 women who were disease-free at the start of the study, and followed up for 26 years. Researchers also measured blood levels of magnesium in 99 women who had a fatal heart attack during this time, and compared them to 291 women in the study of similar age, ethnicity, smoking habits, and cardiovascular condition who did not have a heart attack.
Women with the highest magnesium levels were 37 percent less likely to have a fatal heart attack than those with the lowest levels. Scientists also found a direct link: each 0.25 mg increase in magnesium per deciliter of blood meant a 41 percent lower chance of heart attack.