Iron: A Vegan Nutrition Primer

Iron: A Vegan Nutrition Primer 2017-05-24T07:15:22+00:00

lentil soupGetting plenty of iron on a vegan diet is easy. Plant foods can be among the richest sources of this nutrient. For example, ½ cup of cooked lentils has nearly twice the iron as four ounces of beef—a food generally thought of as an iron superstar. It’s not surprising that vegans and vegetarians often consume more iron than meat-eaters (1).

But vegans also have somewhat higher iron requirements according to the Food and Nutrition Board (FNB) which is the group that establishes iron recommendations for Americans. Because iron from plant foods isn’t absorbed as well as iron from meat, the FNB says that vegetarians may need nearly twice as much. Determining true iron requirements for vegans and vegetarians isn’t quite that straightforward, though, as you’ll see below.

Iron in the Body

Iron is an important part of red blood cells and is needed to form hemoglobin which transports oxygen throughout the body. Although we recycle the iron in red blood cells, we still lose some of this mineral every day, mostly from the skin and intestines. Women also lose iron through menstruation. This is why younger women have much higher iron requirements than men or than women who no longer have their periods.

Iron-deficiency anemia occurs when the body doesn’t have enough iron to support normal red blood cell production. It’s a serious and relatively common public health problem. But getting too much iron can be harmful, too, causing excessive amounts to be stored in the body. There is some evidence that this raises risk for type 2 diabetes and possibly for other chronic diseases as well (2).

To some extent, the body regulates absorption of iron to keep stores from dropping too low or building to dangerously high levels. That is, how much iron you absorb is related to the size of your iron stores. Interestingly, though, the type of iron found in plant foods, called non-heme iron, is much more sensitive to these checks and balances compared to heme iron, which occurs exclusively in animal flesh (3).

Iron Absorption from Plants

While absorption of iron from plants varies based on need, it’s generally quite a bit lower than absorption of iron from meat. The main reason is that iron-rich plant foods are often high in phytic acid (also called phytate) a compound that binds iron and other minerals.

Phytic acid is definitely not all bad, since it’s a powerful antioxidant that may be associated with lower risk for cancer (4,5). The key is not to avoid phytate—and you really can’t since it’s abundant in whole grains, beans, nuts and seeds—but rather to eat in a way that minimizes its effect on iron. For example, adding vitamin C-rich foods to a meal counters the effects of phytate and increases iron absorption. The effects of vitamin C can be pretty dramatic. A small serving of a vitamin C-rich food—like a glass of orange juice or ½ cup of cauliflower—has been shown to increase iron absorption from plant foods by as much as four to six times (6,7). In fact, poor iron status may sometimes be reversed simply by increasing vitamin C intake as opposed to packing more iron into meals (8).

Fermentation—which occurs when bread is leavened with yeast or sour dough—also improves iron absorption (9). So eating some whole grain bread in place of other grains can improve iron nutrition.

In contrast, compounds in tea and coffee and even in certain herbal teas such as peppermint and chamomile, interfere with iron absorption (10,11). Certain Indian spices such as turmeric and coriander are also high in compounds that can interfere with iron absorption (13). Large doses of calcium also inhibit iron absorption. Vegans may have a distinct advantage over lacto-ovo vegetarians in this regard. Not only are dairy foods lacking in iron, but adding them to meals can reduce iron absorption from other foods (14).

How Much Iron Do Vegans Really Need?

When the Food and Nutrition Board determined that vegetarian iron needs were much higher than those of meat-eaters, they were basing their recommendations on fairly limited research (15,16). This research showed that iron is poorly absorbed from plant-based diets that are high in inhibitors of iron absorption and low in enhancers. Based on the results, they suggested that vegetarians could require as much as 1.8 times more iron than people who eat meat.

But this may not be true for vegans and vegetarians in general for a couple of reasons. One is that people may adapt over time to diets with low iron biovailability by absorbing more and excreting less iron (16, 17). Also, vegans and vegetarians tend to have low (but normal) iron stores (1). Again, lower iron stores are associated with better iron absorption. Finally, vegans have the option of eating diets that maximize iron absorption by eating vitamin C-rich foods as part of meals and avoiding inhibitors with meals. The Food and Nutrition Board didn’t take these issues into consideration in their recommendations.

Even so, vegans typically eat at least as much iron as meat-eaters and often more, but still have lower iron stores. This tells us that vegans and others eating plant-based diets do have higher requirements. But how much higher? Unfortunately, we don’t have the research to answer that question.

Rather than track your intake of iron, the best approach is to eat in a way that maximizes iron intake and absorption.

  • Include plenty of iron-rich foods like beans, soyfoods, nuts, seeds, winter squashes, dark leafy green vegetables, dried fruits, oatmeal, quinoa and pearl barley in your diet.
  • Enriched, refined grains can be very high in iron, but they are low in other nutrients and in fiber. Including some of these foods in vegan diets—especially for children—might help increase iron intake for those who have trouble meeting needs, though.
  • Consider getting some of your grains as whole grain bread. The leavening process makes iron more absorbable.
  • Include a good source of vitamin C in as many meals and healthy snacks as is possible and practical. Foods that are rich in vitamin C include citrus fruits and juices, cantaloupe, kiwifruit, mango, papaya, pineapple, strawberries, broccoli, Brussels sprouts, peppers, tomato juice, cabbage, cauliflower.
  • If you like them, include soyfoods in your diet. The iron in soybeans is in a different form from other plant foods and doesn’t appear to be affected as much by phytic acid (18).
  • Avoid drinking tea, coffee or herbal teas with meals as a rule.
  • Limit calcium supplements to small doses (300 mg) and take them between meals rather than with meals.

Despite lower iron stores, vegans don’t seem to develop iron-deficiency anemia any more often than people who eat meat. Iron deficiency is relatively common overall, though, and especially so in young children and in young women. If you think you might be deficient in this nutrient—if you feel unusually tired or get sick often or are experiencing hair loss—it’s worth having your iron levels tested by your health care provider. If you are deficient, the best way to fix that is to take supplements, not to add meat to your diet.

For more information:

Iron in Vegetarian Diets Fact Sheet from the Vegetarian Nutrition Dietetic Practice Group

VeganHealth

References

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  12. Schlesier K KB, Kiehntopf M, Winnefeld K, Roskos M, Bitsch R, Böhm V. . Comparative evaluation of green and black tea consumption on the iron status of omnivorous and vegetarian people. Food Research International. 2012;46:522-7.
  13. Narasinga R, Prabhavathi T. Tannin content of foods commonly consumed in India and its influence on ionizable iron. J Sci Food Agric 1982:89-96.
  14. Hallberg L, Rossander-Hulten L, Brune M, Gleerup A. Calcium and iron absorption: mechanism of action and nutritional importance. Eur J Clin Nutr 1992;46:317-27.
  15. Cook JD, Dassenko SA, Lynch SR. Assessment of the role of nonheme-iron availability in iron balance. Am J Clin Nutr 1991;54:717-22.
  16. Hunt JR, Roughead ZK. Nonheme-iron absorption, fecal ferritin excretion, and blood indexes of iron status in women consuming controlled lactoovovegetarian diets for 8 wk [see comments]. Am J Clin Nutr 1999;69:944-52.
  17. Armah SM, Boy E, Chen D, Candal P, Reddy MB. Regular Consumption of a High-Phytate Diet Reduces the Inhibitory Effect of Phytate on Nonheme-Iron Absorption in Women with Suboptimal Iron Stores. J Nutr 2015
  18. Lonnerdal B, Bryant A, Liu X, Theil EC. Iron absorption from soybean ferritin in nonanemic women. Am J Clin Nutr 2006;83:103-7