Iron is a necessary nutrient in a healthy diet, but for an estimated 1 million Americans who have a disease called hemochromatosis, it can be deadly.

Hemochromatosis, or iron overload, is a hereditary disease in which the body absorbs too much iron, said Dr. Charles Hazzi, an internist at New York University Medical Center.Iron is normally needed as the main component of hemoglobin, the protein in red blood cells that enables them to carry oxygen throughout the body.

Once considered a rare disease, hemochromatosis is a consequence of a common genetic disorder among Caucasians, with as many as one in 10 carrying the abnormal gene that leads to the problem.

The inherited defect causes the small intestine to absorb much more iron from food than the body really needs. And since iron is not eliminated from the body except through bleeding, the element builds up in the bloodstream, eventually causing possible damage to the liver, heart and pancreas.

Hazzi said the disease can also cause what is called "bronze diabetes" because the iron buildup destroys the insulin-producing cells of the pancreas and darkens the skin.

Symptoms or signs of the disease also include abnormal liver blood tests and occasionally very high levels of glucose. In a physical examination, an enlarged liver or heart may be detected.

Hemochromatosis is diagnosed with a blood test for excess iron, followed up by a liver biopsy to determine the extent of any organ damage.

"If caught early," Hazzi said, "treatment, which consists of removing blood until iron levels are sharply decreased, can prevent major organ damage."

Because most people who have hemochromatosis usually do not know it until they are at least 40 and organ damage has become apparent, Hazzi recommends that iron supplements be avoided unless they are specifically determined to be needed.

"A person with hemochromatosis who takes iron pills will accelerate organ damage. Taking megadoses of vitamin C can also cause excess absorption of iron," Hazzi said.