Vegan for Life - Jack Norris [29]
Foods contain two forms of iron, called heme and nonheme iron. Heme iron is much more readily absorbed by the body and is not much affected by other factors in the diet. Nonheme iron is absorbed at a much lower level, and its absorption can be inhibited or enhanced by other dietary components. Meat contains both types of iron, but plant foods contain only nonheme iron. So using strategies to boost absorption is important for people who get all of their iron from plant foods.
Because phytate reduces iron absorption, all of the food preparation methods we mentioned above—fermentation, leavening breads, soaking, sprouting, and cooking—can boost iron absorption. But the most effective way by far to release iron from phytate is to add vitamin C to meals. The effects of vitamin C on iron absorption are rather dramatic. In one study in India, children with iron-deficiency anemia (who probably did not have high vitamin C intakes) were given 100 milligrams of vitamin C at lunch and dinner for sixty days. Most made a full recovery with a significant improvement in their anemia.3
But simply taking a daily vitamin C supplement won’t improve your iron status, since the iron and vitamin C must be consumed at the same time. So including iron-rich and vitamin C–rich foods in the same meal is important for good iron status. Vitamin C is found in citrus fruits, strawberries, green leafy vegetables (broccoli, kale, collards, swiss chard, brussels sprouts), bell peppers (yellow, red, and green), and cauliflower. Other organic acids in fruits and vegetables may also boost iron absorption. Cooking foods in cast-iron pans can increase iron consumption from acidic foods like tomato sauce.
You should know, however, that certain dietary factors like tannins in coffee and tea and high doses of calcium reduce absorption of nonheme iron. It’s important to take calcium supplements between meals and avoid drinking coffee and tea with meals to maximize iron absorption.
Vegans have a definite advantage over lacto-ovo vegetarians when it comes to iron because milk is a poor source of this mineral. In addition to displacing iron-rich foods from the diet, it interferes with iron absorption. Excessive consumption of milk can increase the risk for iron deficiency, especially in young children.4
Vegan and Vegetarian DRI for Iron
Vegetarians typically have iron stores that are at the lower end of the normal range—that is, lower than the stores of meat-eaters, but still adequate. It’s important to maintain these stores by eating plenty of iron-rich foods. And since nonheme iron is absorbed at a lower rate, vegetarians and vegans need more dietary iron than meat-eaters. But how much more is controversial. The Institute of Medicine established a vegetarian recommendation that is 1.8 times higher for vegetarians than omnivores. But this was based on a (completely unrealistic) test diet that was low in vitamin C and high in factors (like tannins from tea) that reduce iron absorption.5 In other words, it represents a worst-case scenario rather than the way most vegetarians and vegans actually eat.
Based on these recommendations, a premenopausal vegan woman would require 33 milligrams of iron per day. While it’s possible to plan a diet that provides this much iron, it would be extremely difficult to consume this much without supplements. Moreover, in addition to being unrealistic, this amount is probably unnecessary. Vegans who consume vitamin C–rich foods with their meals and who avoid coffee, tea, and calcium supplements with meals are likely to need much less iron than this recommendation. See “Maximizing Iron and Zinc in Vegan Diets” on page 70.
If you are diagnosed with iron-deficiency anemia, it doesn’t mean you should start eating meat. Iron deficiency, even in meat-eaters, is usually treated with supplemental iron, not more meat. Large doses of iron should be taken only under a doctor’s care, however, since megadoses of any mineral can be harmful. There may also be an advantage to taking supplements of the amino acid L-lysine since, in one study