Too much of any vitamin or mineral can be harmful. Excess iron levels have been linked to an increased risk of colon cancer and other serious medical concerns. As discussed below, high iron levels have also been linked in some studies to heart disease, although the link has not yet been proven and remains highly controversial.

Since the 1990s, studies have been conducted to find a link between excess iron levels in the body and heart attacks and stroke. However, so far, the results inconclusive and unreliable. Further research is needed to find a clear association between iron levels, heart attack and stroke.

For example, one study found that men with high levels of iron stored in their body had almost three times the number of heart attacks than men with lower levels of iron. On the other hand, some studies examining the link between high iron levels and atherosclerosis (hardening of the arteries), a strong indicator for heart disease, have yielded contradictory results.

To explain the possible link, some experts suggest that high amounts of iron contribute to oxidation – the harmful process by which LDL (“bad”) cholesterol becomes fatty plaque in the arteries. Other experts believe that high iron levels contribute to the production of oxygen free radicals, which promote the buildup of plaque in the arteries. A 2000 study suggested that high iron levels are associated with greater stroke damage because of their effect on these oxygen free radicals. Because antioxidants such as vitamins A, C, E and selenium counteract both oxidation and oxygen free radicals, it has been further proposed that people who take supplements that contain antioxidants may counter this potentially harmful effect of iron. 

The link between high iron levels and heart disease is strengthened by the fact that women are at a lower risk of heart disease before menopause, when they are having  regular menstrual cycles. After menopause, when menstruation ends, women’s risk of heart disease increases along with the levels of iron in their bloodstream. However, some scientists suggest that the increased risk of heart disease following menopause has more to do with a decrease in estrogen (which is though to protect the body against heart disease) than an increase in iron levels.

It is important to note that, despite the apparent risks of high iron levels, the American Heart Association (AHA) does not recommend that people lower the amount of iron they receive in their diet. Instead, patients who are concerned about their iron levels should consult their physician about the need to lower iron levels.