Iron in the Vegan Diet
by Reed Mangels, Ph.D., R.D.
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Topics in this article:
•Table 1: Iron Content of Selected Vegan Foods
•Table 2: Comparison of Iron Sources
•Table 3: Sample Menus Providing More Than 15 mg of Iron
•Excerpted from the book Simply Vegan: Quick Vegetarian Meals by Debra Wasserman. Nutrition section by Reed Mangels Ph.D., R.D. (ISBN 0-931411-20-3)
Summary
Dried beans and dark leafy green vegetables are especially good sources of iron, better on a per calorie basis than meat. Iron absorption is increased markedly by eating foods containing vitamin C along with foods containing iron. Vegetarians do not have a higher incidence of iron deficiency than do meat eaters.
Heme vs. Non-heme Iron
Iron is an essential nutrient because it is a central part of hemoglobin which carries oxygen in the blood. Iron deficiency anemia is a worldwide health problem which is especially common in young women and in children.
Iron is found in food in two forms, heme and non-heme iron. Heme iron, which makes up 40 percent of the iron in meat, poultry, and fish is well absorbed. Non-heme iron, 60 percent of the iron in animal tissue and all the iron in plants (fruits, vegetables, grains, nuts) is less well absorbed. Some might expect that since the vegan diet contains a form of iron which is not that well absorbed, vegans might be prone to developing iron deficiency anemia. However, recent surveys of vegans and vegetarians [1, 2, 3] have shown that iron deficiency anemia is no more common among vegetarians than among the general population.
Iron Status in Vegans
The reason for the satisfactory iron status of many vegans may be that commonly eaten foods are high in iron, as Table 1shows. In fact, if the amount of iron in these foods is expressed as milligrams of iron per 100 calories, many foods eaten by vegans are superior to animal-derived foods. This concept is illustrated in Table 2. For example, you would have to eat 340 calories of sirloin steak to get the same amount of iron as found in 100 calories of spinach.
Another reason for the satisfactory iron status of vegans is that vegan diets are high in vitamin C. Vitamin C acts to markedly increase absorption of non-heme iron. Adding a vitamin C source to a meal increases non-heme iron absorption up to six-fold which makes the absorption of non-heme iron as good or better than that of heme iron [4].
Fortunately, many vegetables, such as broccoli and bok choy, which are high in iron are also high in vitamin C so that the iron in these foods is very well absorbed. Commonly eaten combinations, such as beans and tomato sauce or stir-fried tofu and broccoli, also result in generous levels of iron absorption.
It is easy to obtain plenty of iron on a vegan diet. Table 3 shows several menus which would meet the RDA [5] of 15 milligrams of iron per day for an adult woman. Men and post-menopausal women need about one-third less iron, 10 milligrams daily.
Both calcium and tannins (found in tea and coffee) reduce iron absorption. Tea, coffee, and calcium supplements should be used several hours before a meal which is high in iron [6].
References
1. Anderson BM, Gibson RS, Sabry JH: The iron and zinc status of long-term vegetarian women. Am J Clin Nutr 1981; 34: 1042-1048.
2. Latta D and Liebman M: Iron and zinc status of vegetarian and non-vegetarian males. Nutr Rep Int 1984; 30: 141-149.
3. Helman AD and Darnton-Hill I: Vitamin and iron status in new vegetarians. Am J Clin Nutr 1987; 45: 785-789.
4. Hallberg L: Bioavailability of dietary iron in man. Ann Rev Nutr 1981; 1: 123-147.
5. Food and Nutrition Board, National Research Council: Recommended Dietary Allowances, 10th ed. Washington, DC: National Academy Press, 1989.
6. Gleerup A, Rossander Hulthen L, Gramatkovski E, et al. Iron absorption from the whole diet: comparison of the effect of two different distributions of daily calcium intake. Am J Clin Nutr 1995; 61: 97-104.