Vegan 101: Can plant foods provide enough iron?

Examiner.com - Friday, August 28, 2009

By Virginia Messina, MPH, RD, Seattle Vegan Examiner

It's a myth that vegan diets are low in iron. Studies show that vegans consume at least as much iron as omnivores and sometimes more. Vegans definitely have an advantage over lacto-ovo vegetarians when it comes to iron since dairy foods don’t contain this mineral. It’s true, however, that iron from plant foods isn't absorbed as well as from animal foods.

Most iron is found in hemoglobin, the blood component responsible for transporting oxygen throughout the body. Much of the rest of it is stored in the liver, spleen and bone marrow as a form of iron called ferritin.

Vegans tend to have lower iron stores than omnivores, but there is actually no known advantage to having higher stores of iron. In fact, there is some evidence that the lower iron stores seen in those eating plant-based diets is associated with better glucose tolerance which could reduce risk for diabetes.If stores drop below what is normal, however, hemoglobin production is affected. Low hemoglobin values indicate iron deficiency.

Iron is lost through normal shedding of intestinal cells, perspiration and urine, and also via blood loss. Premenopausal women have higher iron needs than men because they have significant losses through menstruation.

Getting enough iron on a vegan diet

The type of iron in plant foods is sensitive to a number of factors that can either decrease absorption or boost it. For those eating a plant based diet, managing those factors is every bit as important as getting adequate iron.

Here are some ways to maximize iron absorption:

Avoid coffee and tea with meals since they contain compounds called tannins that inhibit iron absorption. (Some Indian spices - turmeric, coriander and tamarind - also contain tannins.)

If you use calcium supplements, take them between meals since high doses of calcium also interfere with iron absorption.

Eat more bread than crackers; leavening (by yeast) makes iron more absorbable.

Eat a good source of vitamin C with every meal and snack. Vitamin C is one of the best ways to increase iron absorption but it must be consumed at the same time as the iron-rich food.

Do vegans and vegetarians have higher iron requirements?

Because of lower bioavailability of iron from plant foods, the Food and Nutrition Board established separate iron RDAs for vegetarians and vegans. For pre-menopausal women, they suggested getting 33 milligrams per day compared to 18 for omnivore women - nearly twice as much. They recommended 14 milligrams for vegetarian men.

Their recommendations weren’t based on studies of actual vegetarian populations, though. Rather they used a test diet that was designed to reduced iron absorption; it was high in factors that inhibit iron absorption and low in vitamin C. In essence, it was kind of a worst case scenario. And it is not at all the way most vegans eat.

There is no reason to think that vegans who pay attention to maximizing iron absorption actually need those very high iron intakes. In addition, there is evidence that vegetarians adapt to lower iron intakes over time. Most vegan and vegetarian women don’t consume 33 milligrams of iron per day and are not iron deficient as a result.

Those who eat a variety of plant foods and include good sources of vitamin C with meals can be assured that their iron needs will be met. Good sources of vitamin C include melons, citrus fruits, pineapple, strawberries, kiwifruit, broccoli, peppers, tomatoes, and potatoes. Include some of these foods at every meal!

Here are some of the best sources of iron (measured in milligrams of iron):

1/2 cup firm tofu - 6.6
1/2 cup soybeans - 4.4
1 tbsp blackstrap molasses - 3.5
1/2 cup lentils - 3.3
1/2 cup spinach - 3.2
2 tbsp tahini - 2.7
1/2 cup kidney beans - 2.6
2 tbsp pumpkin seeds - 2.5
1/2 cup chickpeas - 2.4
1/2 cup Swiss chard - 2.0
1/4 cup dried apricots - 1.5