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Iron in the vegan diet

Posted on: July 22, 2012

Iron in the Vegan Diet

by Reed Mangels, Ph.D., R.D.

Topics in this article:

Summary

Dried beans and dark green leafy vegetables are especially good sources of iron, even 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 that 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. Vegan diets only contain non-heme iron. Because of this, iron recommendations are higher for vegetarians (including vegans) than for non-vegetarians. The RDA for iron is 14 milligrams per day for vegetarian men and for women after menopause, and 33 milligrams per day for women prior to menopause 1.

Iron Status in Vegans

Some might expect that since the vegan diet contains a form of iron that is not that well absorbed, vegans might be prone to developing iron deficiency anemia. However, surveys of vegans 2,3 have found that iron deficiency anemia is no more common among vegetarians than among the general population although vegans tend to have lower iron stores 3.

The reason for the satisfactory iron status of many vegans may be that commonly eaten foods are high in iron, as Table 1 shows. 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 more than 1700 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 iron on a vegan diet. Table 3 shows several menus that would meet the RDA for iron.

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 that is high in iron 5.

Table 1: Iron Content of Selected Vegan Foods
Food Amount Iron (mg)
Soybeans, cooked 1 cup 8.8
Blackstrap molasses 2 Tbsp 7.2
Lentils, cooked 1 cup 6.6
Spinach, cooked 1 cup 6.4
Quinoa, cooked 1 cup 6.3
Tofu 4 ounces 6.0
Bagel, enriched 3 ounces 5.2
Tempeh 1 cup 4.8
Lima beans, cooked 1 cup 4.4
Swiss chard, cooked 1 cup 4.0
Black beans, cooked 1 cup 3.6
Pinto beans, cooked 1 cup 3.5
Turnip greens, cooked 1 cup 3.2
Chickpeas, cooked 1 cup 3.2
Potato 1 large 3.2
Kidney beans, cooked 1 cup 3.0
Prune juice 8 ounces 3.0
Beet greens, cooked 1 cup 2.7
Tahini 2 Tbsp 2.7
Veggie hot dog 1 hot dog 2.7
Peas, cooked 1 cup 2.5
Black-eyed peas, cooked 1 cup 2.3
Cashews 1/4 cup 2.1
Brussels sprouts, cooked 1 cup 1.9
Bok choy, cooked 1 cup 1.8
Bulgur, cooked 1 cup 1.7
Raisins 1/2 cup 1.6
Almonds 1/4 cup 1.5
Apricots, dried 15 halves 1.4
Veggie burger, commercial 1 patty 1.4
Watermelon 1/8 medium 1.4
Soy yogurt 6 ounces 1.1
Tomato juice 8 ounces 1.0
Green beans, cooked 1 cup 1.2
Kale, cooked 1 cup 1.2
Sunflower seeds 1/4 cup 1.2
Broccoli, cooked 1 cup 1.1
Millet, cooked 1 cup 1.1
Sesame seeds 2 Tbsp 1.0
Sources: USDA Nutrient Database for Standard Reference, Release 18, 2005 and Manufacturer’s information.

The RDA for iron for vegetarians is 14 mg/day for adult men and for post-menopausal women and 33 mg/day for pre-menopausal women.

 

Table 2: Comparison of Iron Sources
Food Iron
(mg/100 calories)
Spinach, cooked 15.7
Collard greens, cooked 3.1
Lentils, cooked 2.9
Broccoli, cooked 1.9
Hamburger, lean, broiled 1.2
Chickpeas, cooked 1.1
Sirloin steak, choice, broiled 0.9
Chicken, breast roasted, no skin 0.6
Pork chop, pan fried 0.4
Flounder, baked 0.3
Milk, skim 0.1
Note that the top iron sources are vegan.

 

Table 3: Sample Menus Providing
Generous Amounts of Iron
Iron (mg)
Breakfast:
1 serving Oatmeal Plus (p. 23) 3.8
Lunch:
1 serving Tempeh/Rice Pocket Sandwich (p. 94) 4.7
15 Dried Apricots 1.4
Dinner:
1 serving Black-Eyed Peas and Collards (p. 76) 2.1
1 serving Corn Bread (p. 21) 2.6
1 slice Watermelon 1.4
TOTAL 16.0

Breakfast:
Cereal with 8 ounce of Soy Milk 1.5
Lunch:
1 serving Creamy Lentil Soup (p. 49) 6.0
1/4 cup Sunflower Seeds 1.2
1/2 cup Raisins 1.6
Dinner:
1 serving Spicy Sautéed Tofu with Peas (p. 103) 14.0
1 cup Bulgur 1.7
1 cup Spinach 6.4
sprinkled with
2 Tbsp Sesame Seeds 1.0
TOTAL 33.4
Additional foods should be added to these menus to provide adequate calories and to meet requirements for nutrients besides iron.

References

  1. Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, DC: National Academy Press, 2001.
  2. Haddad EH, Berk LS, Kettering JD, Hubbard RW, Peters WR. Dietary intake and biochemical, hematologic, and immune status of vegans compared with nonvegetarians. Am J Clin Nutr 1999;70(suppl):586S-93S.
  3. Obeid R, Geisel J, Schorr H, et al. The impact of vegetarianism on some haematological parameters. Eur J Haematol. 2002;69:275-9.
  4. Hallberg L. Bioavailability of dietary iron in man. Ann Rev Nutr 1981;1:123-147.
  5. 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.

SIMPLY VEGAN COVER This article originally appeared in the book Simply Vegan: Quick Vegetarian Meals by Debra Wasserman. Nutrition section by Reed Mangels Ph.D., R.D. (ISBN 0-931411-30-0)
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