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Factors affecting iron absorption Iron deficiency can result in a confusing array of symptoms, including fatigue and weakness, poor work performance, increased risk of infections, difficulty keeping warm, lightheadedness, rapid heartbeat and shortness of breath with exercise. Studies have suggested that people who engage regularly in strenuous exercise, especially adolescents and vegetarians, are at increased risk of developing iron-deficiency anemia. Iron deficiency is rare in men and postmenopausal women, and most should avoid supplements containing iron to reduce the risk of organ damage from too much iron. Also, if a routine blood test indicates low iron, experts warn against simply taking a supplement. Rather, a doctor should first check for hidden blood loss or impediments to iron absorption resulting from diet habits, medications or chronic health conditions, like colitis or the aftermath of weight-loss surgery. There are two kinds of dietary iron, heme and nonheme. Heme iron, found only in meat, fish and poultry, is much better absorbed that the nonheme iron found in vegetables, fortified foods, supplements and acidic foods cooked in cast-iron pots. Whereas 15 to 30 percent of heme iron consumed is absorbed, only 5 percent of nonheme iron gets into the blood. To assure adequate iron absorption, some vegans and vegetarians may need to take a supplement. Various factors can affect iron absorption. Some vegetables, like spinach (Popeye notwithstanding), contain oxalic acid, which interferes with iron absorption. High-fiber foods like whole grains that contain phytates and foods high in calcium also diminish the amount of iron that enters blood. But the vitamin C and other acids naturally present in fruits, fruit juices and some vegetables increase iron absorption. In a subsequent study by the Framingham researchers, men and women ages 68 to 93 had the highest levels of stored iron if they consumed red meat four or more times a week, took more than 30 milligrams of an iron supplement daily or ate more than 21 servings of fruit each week. However 更多：https://www.bmcx.com/ , levels were much lower among those who consumed more than seven servings of whole grains each week. Hazards of iron overload Earlier this year, Nutrition Action Healthletter, published by the Center for Science in the Public Interest, summarized the latest evidence for the effects of excess iron stores. The problem with too much stored iron is that, short of bleeding, the body can't easily get rid of it. Menstruating women are unlikely to have a problem, but for others with high stores the recommended treatments include phlebotomy and frequent blood donation. Without these measures, excess iron is deposited in the liver, heart and pancreas, where it can cause cirrhosis, liver cancer, cardiac arrhythmias and diabetes. These health consequences can develop even in people without hemochromatosis, the genetic disorder, who accumulate very high levels of stored iron. For example, among 32,000 women followed for 10 years in the Nurses' Health Study, those with the highest levels of stored iron were nearly three times as likely to have diabetes as those with the lowest levels. Likewise, among 38,000 men in the Health Professionals Follow-up Study, those who consumed the most heme iron had a 63 percent greater risk of developing diabetes. While the risk of cancer from too much iron is uncertain except in people with hemochromatosis, the known links between high levels of red meat consumption and cancers of the colon and prostate are highly suggestive of an increased risk associated with excessive consumption of heme iron. As for heart disease, the link found in some studies to high levels of heme iron consumption may reflect the effect of saturated fats from red meat, the richest source of heme iron, more than that of iron itself. High levels of iron have been found in the brains of people with neurodegenerative diseases like Alzheimer's, Parkinson's and amyotrophic lateral sclerosis (Lou Gehrig's disease). But sick brain cells accumulate abnormal levels of minerals like aluminum, so iron in these cases may be an effect of brain disease rather than its cause. Nonetheless, there are ample health and environmental reasons to limit consumption of red meat to no more than two or three times a week and to focus more on poultry, seafood and plant sources of protein.