Iron deficiency in U.S. worries health experts
Despite the fact that the United States fortifies many food products with iron, the Centers for Disease Control report that the incidence of nonanemic iron deficiency is increasing. This trend is surprising because nonanemic iron deficiency is decreasing in other parts of the world.
Question: What foods are typically fortified with iron?
Answer: The U.S. food laws require that all-purpose white flour be enriched with iron. Therefore white bread and most bread products, pasta, breakfast cereals, energy bars and even cookies contain added iron.
Q: If so many common foods contain extra iron, why is iron deficiency a problem?
A: The iron that is added to most of these products is in the form of elemental iron particles. These iron "shavings" do not readily dissolve in the stomach and are poorly absorbed by the intestine. As a consequence, people are not consuming as much "absorbable iron" as it might appear from the amounts listed on food labels.
In addition, there are common dietary factors that enhance or inhibit the absorption of iron from foods. Absorption is enhanced when iron in foods or supplements is consumed with vitamin C, beta-carotene, meat, fish or poultry.
Combinations of some foods cause less iron to be absorbed. For example, when coffee, tea or milk is consumed with iron-containing foods or supplements, less iron is absorbed. In general, calcium supplements and high-calcium foods substantially block iron absorption from other foods or supplements when consumed at the same time.
Foods like red wine and red beans contain high levels of compounds called polyphenols that inhibit absorption of iron. The high levels of both polyphenols and calcium found in spinach result in extremely poor absorption of its iron.
Q: How well is the iron in supplements absorbed?
A: The most common iron supplements contain iron (ferrous) sulfate. Since this form of iron is poorly absorbed, most iron supplements typically prescribed contain a rather high dosage to make up for the poor absorption. Unfortunately, the high dose often causes intestinal problems such as constipation or diarrhea, and people stop taking the supplement before their iron status is back to normal.
Other types of iron supplements such as ferrous fumarate or ferrous gluconate are often better tolerated, but iron absorption is still limited. Supplements containing the better-absorbed heme iron form can be taken in much lower doses with fewer side effects. For full benefit, iron supplementation needs to be supported by a diet that contains adequate protein and all other essential nutrients.
Alan Titchenal, Ph.D., C.N.S. and Joannie Dobbs, Ph.D., C.N.S. are nutritionists in the Department of Human Nutrition, Food and Animal Sciences, College of Tropical Agriculture and Human Resources, University of Hawaii-Manoa. Dr. Dobbs also works with University Health Services.