Iron absorption, iron overload, causes and symptoms
The body can utilize two types of iron—heme, which comes from animal sources, and nonheme, which comes from plants. The body absorbs 20 to 30 percent of heme iron, compared with 5 to 10 percent of nonheme. When the body’s iron reserves are low, the absorption of nonheme iron increases. Consuming iron-rich plant foods with meat or with good sources of vitamin C boosts nonheme iron absorption. By the same token, some substances for example, tea, bran, and the oxalates found in spinach and kale—decrease the body’s absorption.
Genetic factors influence iron absorption. About 10 percent of whites and up to 30 percent of people of African descent carry a gene that predisposes them to store extra iron. The presence of a single gene does not cause problems, but if a person inherits the gene from both parents, he is likely to develop iron overload, or hemochromatosis. Men and postmenopausal women are especially vulnerable.
An iron overload does not produce symptoms until a damaging amount has accumulated in muscle tissue (including the heart), the liver, bone marrow, the spleen, and other organs; this usually occurs during middle age. One of the first indications is a ruddy complexion; the person may also suffer fatigue, joint and intestinal pain, and an irregular heartbeat. As the liver becomes damaged, jaundice may develop.
A blood test can be used to diagnose an iron overload; in some cases, a liver biopsy may also be ordered. Treatment involves periodic removal of a pint (0.5 liter) or so of blood, which reduces iron levels by forcing the body to use some of its stores to make new red blood cells.
Even moderately elevated iron levels may set the stage for heart disease. One study reported that men whose blood iron levels were in the high-normal range were more likely to develop coronary artery disease than those with low-to-normal levels. This supports the theory that excessive iron may injure the artery walls and promote the formation of fatty deposits. This damage may be due to iron’s ability to catalyze oxidation processes. Controversy continues over iron and heart disease risk, with some studies showing that only heme iron was linked with heart disease and others finding no link. Some researchers also think that iron may contribute to the joint pain and damage that many women endure following menopause. The message continues to be that you should only take supplements if you are iron deficient.
Foods high in vitamin C, which enhances iron absorption, should not be consumed with iron-rich plant foods by those who are predisposed to store extra iron. Unless prescribed by a doctor, supplements containing iron and large doses of vitamin C should not be taken. Some experts now advise that anyone who is contemplating taking a vitamin C supplement should first have a blood test to measure iron levels.
