Many people worry about getting too little iron—for good reason. Iron, after all, is essential to life. Most iron in our bodies is incorporated in hemoglobin, which carries oxygen in the blood, and in myoglobin in muscle, but every living cell has and needs iron to function.
Iron is also stored in the liver, spleen and bone marrow. Without it, your cells would become starved for oxygen, your brain and muscles wouldn’t function, and your immune system would be impaired, among other problems.
But that doesn’t mean most people need to take an iron supplement—or even a multivitamin/mineral pill that contains iron. In fact, too much iron can be dangerous.
Ironing out the facts
Survival of the species depended on humans evolving to maintain iron stores during reproductive and early care-giving years. Having enough iron in reserve is essential for growth, healthy pregnancies, and periods of dietary restrictions and starvation, and it helps replace iron lost via menstruation and other blood loss.
But the flip side of iron is less rosy. There’s increasing evidence from population, genetic, lab and animal studies that iron accumulation over the years may contribute to conditions such as atherosclerosis and diabetes, and that iron may speed up the aging process in general. Iron can be toxic to the nervous system and has been linked to a variety of neurological conditions, from strokes to Alzheimer’s and Parkinson’s disease.
As a 2007 review from the University of Michigan Medical School hypothesized, iron fuels the generation of cell-damaging free radicals, which “takes its toll in the later years of life.” That is, an iron level that is desirable earlier in life during growth and reproduction may not be beneficial later in life. The body has natural antioxidant protective mechanisms that help fend off free radicals, but they are not 100 percent effective, especially during times of stress. Over the course of normal aging, the damage accumulates.
A review paper published in Diabetes Care a few years ago noted a link between higher iron and diabetes, as well as improvements in blood sugar control when iron stores are reduced, such as through blood donation. Another paper, from Indiana University in 2007, noted that excess iron has been linked to many conditions, including colorectal cancer, hypertension and stroke.
Of course, associations between higher iron levels and disease do not prove cause and effect. In fact, results of studies have been mixed. A Finnish study from 1992, for example, found that men with higher ferritin (the main iron storage protein) were twice as likely to have a heart attack as men with lower levels, but more recent studies have failed to confirm this.
Moreover, there are no controlled clinical trials to see if lowering iron stores actually reduces atherosclerosis, Alzheimer’s or other conditions. Still, some experts recommend that older people avoid supplemental iron.
The no-iron list
People with hemochromatosis, in particular, should avoid excess iron. This hereditary disorder, which affects more than one million Americans (mostly of northern European descent), causes overabsorption and storage of iron. Left untreated, this leads to weakness, headaches, darkening of skin, sexual dysfunction, joint pain and eventually diabetes, arthritis, liver disease and/or heart failure.
Get tested for hemochromatosis if you have a family history of it or develop symptoms that may be related to it. A simple blood test helps diagnose it. Many doctors recommend routine screening for hemochromatosis in middle age, especially for Caucasians. If you have the disorder, you must limit consumption of iron, especially heme iron (the kind found in meat), and avoid supplements. Donating blood regularly is commonly recommended.
About 10 to 15 percent of Americans carry only one gene for hemochromatosis (two genes, one from each parent, are needed to develop the full-blown disorder) and may accumulate slightly higher-than-average stores of iron. Other genes besides those involved in hemochromatosis can also result in iron overload.
Easy does it on iron
The following people, in general, don't need supplemental iron—and may be better off without it:
• Postmenopausal women. Data from the large Framingham study suggest that the low risk of heart disease among premenopausal women may not be due to hormones alone. It may also be attributable to menstruation and thus the monthly loss of iron. After menopause, when menstruation stops, women begin to catch up to men in heart disease risk. This suggests that higher iron stores may be a factor in the increasing rates of heart disease seen in postmenopausal women.
• Men. Unless they have a condition that causes chronic blood loss, men don’t need supplemental iron.
• Don’t worry about iron in food. It’s hard to get too much iron through diet alone, unless you have hemochromatosis. Moreover, iron absorption in healthy people is well regulated, so absorption is very low if iron reserves are high, says Fernando Viteri, M.D., an iron expert and professor emeritus at the University of California, Berkeley. Still, be aware that if you eat a lot of iron-fortified foods, you may be getting more iron than you need. Some fortified breakfast cereals, for example, contain 100 percent of the Daily Value for iron.
• Consume plenty of fruits and vegetables, which are high in antioxidants. Some researchers suggest that antioxidants may help counteract the action of iron-associated free radicals.
• If you are a postmenopausal woman or a man and take a multivitamin/mineral pill, check the label for iron. Unless your doctor has told you that you are iron-deficient, look for one that has no iron. The iron is unnecessary. Many multis marketed for men and older people do not contain iron.
Originally published February 2011. Updated April 2013.