Offering another reason to go easy on those burgers and steaks, a large study suggests that high iron intake from meat may raise the risk of type 2 diabetes.

The findings, published in the journal Diabetes Care, add to evidence that too much heme iron - the form of the mineral found in meat - may contribute to diabetes through long-term damage to body cells.

Harvard researchers found that among 85,000 women followed for 20 years, the risk of developing type 2 diabetes climbed in tandem with heme iron consumption. Women who ate the most heme iron had a 28 percent higher risk than those with the lowest intakes, even with factors like body weight, exercise and overall diet considered.

Iron from plant foods and supplements, which is not as readily absorbed as heme iron, was unrelated to diabetes risk, according to Dr. Swapnil Rajpathak and colleagues at Harvard Medical School in Boston.

The findings offer yet another reason to eat only moderate amounts of red meat, the prime source of heme iron in the diet, said Rajpathak, who is now at the Albert Einstein College of Medicine in New York.

Though it’s not fully clear why too much iron might contribute to type 2 diabetes, Rajpathak told Reuters Health, the mineral is involved in many body processes that generate reactive oxygen species.

In excess, these molecules create a state of “oxidative stress” that damages body cells over time. Oxidative stress could theoretically set the stage for diabetes by reducing body cells’ sensitivity to the hormone insulin, Rajpathak explained.

The recommended iron intake is 18 milligrams (mg) per day for premenopausal women, and 8 mg for men and for women older than 50. Fish, chicken and pork are much lower in heme iron than red meat is; non-heme iron is found in beans, lentils, spinach and fortified cereals.

SOURCE: Diabetes Care, June 2006.