NEW YORK (Reuters Health) -- Men who consume large amounts of "heme" iron in their diets have an increased risk of developing gallstone disease, according to findings published in the American Journal of Clinical Nutrition.

Heme iron, one of two types of iron found in foods, is bound to either the blood protein hemoglobin or the muscle protein myoglobin. While heme iron, which comes from consumption of meat, poultry, and fish, contributes a smaller portion of iron to typical western diets than non-heme iron, it is more readily absorbed from the gastrointestinal tract. Experimental studies have shown that excessive iron intake can promote gallstone formation, Dr. Chung-Jyi Tsai, of the University of Kentucky Medical Center, Lexington, and colleagues state. "However, the effect of long-term consumption of heme and non-heme iron on the risk of gallstones is unknown."

The researchers evaluated dietary levels of heme and non-heme iron and the risk of gallstones in 44,758 U.S. men participating in the Health Professionals Follow-up Study from 1986 to 2002.

A total of 2,468 cases of gallstones were documented during the follow-up period. Of these, 1,453 men required removal of the gallbladder. High levels of heme iron in the diet raised the risk of developing gall stones by 21 percent, whereas high levels of non-heme iron seemed to have no effect.

In general, continuous, ingestion of large amounts of iron may cause "substantial harm," the researchers add, because the body has no way of excreting excess iron in cases of dietary overload.