A Bone-Building Mineral You Haven’t Thought Of: Iron

January 2004 Tufts University Health & Nutrition Letter

Think minerals needed for strong bones, and you probably think calcium. But there’s another bone-strength-ening mineral worthy of your attention: iron.

In a study of almost 250 postmenopausal women in their 40s, 50s, and 60s, scientists at the Universities of Arizona and Arkansas along with investigators at Columbia University found that those women whose daily iron consumption hovered around at least 18 milligrams had the greatest bone mineral density. The findings come as something of a surprise because the Recommended Dietary Allowance for women who no longer lose iron-rich blood every month is set at only 8 milligrams, while 18 milligrams is the number reserved for women who still menstruate.

Why would iron be so important for bone density? It promotes the production of collagen, a central component of bone.

Interestingly, the finding that iron intake is associated with higher bone density held true only for women who consumed between 800 and 1,200 milligrams of calcium daily. Less—or more—calcium, and that much iron did not appear to be of any bone-building help. The likely reason, comments lead researcher Margaret M. Harris, PhD, who conducted the study from the University of Arizona’s Department of Nutrition Sciences, is that “the most important factor here is mineral balance.” Calcium and iron can compete with each other for absorption by the body—and too much or too little of one or the other throws things off.

The best sources of dietary iron are beef, poultry, and fish, although beans are also a reasonable source. The mineral is particularly well absorbed when consumed with a food that contains vitamin C—the tomato sauce in a bean-based chili, for example, or the red or green pepper in a salad that you have with some steak.

Most multivitamins also contain some iron, but iron supplements are not advised unless recommended by a physician. Too much can cause constipation and raises the risk for iron overload in some people.

It should be pointed out that in the current research, iron may simply be a marker for a good, bone-protecting diet in general or for some other nutrient. Indeed, Dr. Harris points out that iron and calcium are only two of many nutrients important for bone health. There’s also phosphorus, vitamins D and K, and a number of other vitamins and minerals, all of which are best consumed regularly from a variety of healthful foods throughout the day.

Source: Tufts University Health & Nutrition Letter, January 2004. Online at http://healthletter.tufts.edu/issues/2004-01/iron.html.

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