Vegan For Life
by Jack Norris, RD &
Ginny Messina, MPH, RD
- Iron Deficiency and Anemia
- Meat Iron vs. Plant Iron
- Iron Deficiency in Vegetarians
- Low Iron Stores: Not Necessarily Unhealthy
- Celiac Disease
- Proton Pump Inhibitors
If you think your iron stores might be low, you can increase iron absorption by:
- Adding a source of vitamin C at meals.
- Avoiding tea and coffee at meals.
- Increasing legume (peanuts, beans, lentils, peas) intake.
- Cooking foods (especially water based acidic foods like tomato sauce) in cast iron skillets.
If you think you might have iron deficiency anemia, see a doctor to find out. Supplements are available for people diagnosed with deficiency.
Iron deficiency is the most common nutrient deficiency in the U.S. There are two types of iron problems:
- Iron deficiency (ID) - low iron stores; typically measured by a serum ferritin of less than 18 ng/mL (nanograms per millilitre.)
- Iron deficiency anemia (IDA) - typically measured by a hemoglobin of less than 120 g/L (grams per liter.)
IDA symptoms include pale skin, brittle fingernails, spoon-shaped nails (koilonychia), fatigue, weakness, difficulty breathing upon exertion, inadequate temperature regulation, loss of appetite, apathy, and hair loss. Many of these are symptoms of other nutritional deficiencies and diseases and therefore only a medical doctor can properly diagnose IDA. It is relatively inexpensive to have your iron levels tested by a doctor.
Some health professionals believe in "sub-clinical iron deficiency" in which someone has blood measurements in the normal range but is still having symptoms of ID or IDA. According to the National Academy of Sciences, "The bulk of experimental and epidemiological evidence in humans suggests that functional consequences of iron deficiency (related both to anemia and tissue concentration) occur only when iron deficiency is of a severity sufficient to cause a measurable decrease in hemoglobin concentration (1)." However, other iron experts suggest that some people have a higher-than-average normal hemoglobin level and can suffer from IDA even though their hemoglobin is in the (presumably lower end of the) normal range.
|Table 1. Iron Content of Common Foods|
|fortified cereals||1/2 C||varies|
|blackstrap molasses||1 T||3.3|
|pumpkin seeds||2 T||2.5|
|pinto beansa||1/2 C||2.2|
|apricots, dried||1/4 C||1.5|
|aCooked. | C = cup. | T = tablespoon.|
Iron is prevalent in a wide variety of plant foods, especially beans and grains. In fact, vegans' iron intakes are as high or higher than non-vegetarians. Table 1 shows the iron content of some plant foods as well as the Dietary Reference Intakes for iron.
In meat, 65% of iron is bound to the heme molecule (from hemoglobin and myoglobin), which is relatively easily absorbed. The rest of the iron in meat and all iron in plants is non-heme iron (3). Non-heme iron requires being released from food components by hydrochloric acid and the digestive enzyme pepsin in the stomach (3). Non-heme iron also needs to be shuttled from the digestive tract into the bloodstream by a protein called transferrin.
The phytates, found in legumes and grains, and polyphenols (including tannins found in coffee and green tea, black tea, and some herbal teas), can inhibit the absorption of plant iron. On the other hand, vitamin C is a strong enough enhancer of plant iron and can overcome the inhibitors in plant foods.
One study found that various doses of phytate reduced iron absorption by 10 to 50%. But adding 50 mg of vitamin C counteracted the phytate, and adding 150 mg of vitamin C increased iron absorption to almost 30%. Similarly, in the presence of a large dose of tannic acid, 100 mg of vitamin C increased iron absorption from 2 to 8% (13).
In another study, vegetarian children with IDA and low vitamin C intakes in India were given 100 mg of vitamin C at both lunch and dinner for 60 days. They saw a drastic improvement in their anemia, with most making a full recovery (2).
Researchers used 500 mg of vitamin C twice daily after meals to increase hemoglobin and serum ferritin in Indian vegetarians. They concluded that vitamin C was more effective at increasing iron status than iron supplements (12).
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.
Polyphenols, which include tannic acid, can inhibit iron absorption, and are found in coffee, cocoa, and black, green and many herbal teas. You should avoid these foods at meals if you are trying to increase iron absorption (14). One study showed that, over four weeks, green and black tea lowered iron levels primarily in people with serum ferritin levels less than 20 µg/l (15). Calcium supplements can also inhibit iron absorption if taken with meals.
Cooking foods in cast iron pans can increase iron consumption. A 2007 study in Brazil showed that cooking tomato sauce in an iron skillet increases the amount of iron in the sauce and also increased iron status among teen-aged and young adult lacto-ovo vegetarians (9). The authors considered it important for the food cooked to be both acidic and water-based, such as tomato sauce.
The amino acid, L-lysine, plays a part in the absorption of iron and zinc. Among plant foods, L-lysine is only found in high amounts in legumes (peanuts, beans, lentils, peas), and a vegan who doesn't eat many legumes could find themselves falling short on lysine.
The American Dietetic Association's Position Paper on Vegetarian Diets says, "Incidence of iron deficiency anemia among vegetarians is similar to that of nonvegetarians. Although vegetarian adults have lower iron stores than nonvegetarians, their serum ferritin levels are usually within the normal range (8)." This statement is based on cross-sectional studies and, to my knowledge, the iron status of vegetarians or vegans on self-selected diets has never been followed through time.
A 2004 study from Germany (11) found that 40% of premenopausal vegan and near-vegan women had low iron stores, which was four times the national average. The authors recommended that premenopausal women on a vegan diet should have their iron status monitored and should consider taking iron supplements in case of marginal status.
I have met many ex-vegetarian women (and a few men) who claimed to become anemic after becoming vegetarian. In most cases, they did not have a doctor diagnose them but assumed they were anemic because they were tired. This could be due to numerous things, such as not eating enough calories or protein, eating too many high-sugar foods, and possibly not getting enough sleep. However, I have heard it enough to think there is a real possibility that some women have a hard time with the lower iron absorption of plant foods, especially when first becoming vegetarian.
Iron absorption may be more of a problem when people first become vegetarian because long-term studies of vegetarian women have not shown high dropout rates. These studies usually require that someone has been vegetarian for at least a year and anyone who gets IDA within the first few months of becoming vegetarian would not be included in such a study.
Physiologically, it makes some sense that the problem would tend to show up right away or not at all, for the following reason: The body secretes transferrin into the digestive tract when iron stores are low in order to increase absorption of iron into the blood. If someone has been a meat-eater all her life, her body has not had a need to manufacture as much transferrin as she might need as a vegetarian. This might cause a quick drop in iron absorption once she becomes a vegetarian. Someone's body may or may not become more efficient at producing transferrin over time, but if she becomes anemic right away she will likely quit the diet and not give her body the chance.
More evidence of this theory is that I have not heard of any children who were vegan from birth (and otherwise well-nourished and living in a developed country) who developed IDA. Because vegan infants have no prior history of depending on heme iron, they start their lives efficiently absorbing non-heme iron and retain this ability throughout life.
Anemia is a possible downside to lower iron absorption, but there are a few potential upsides:
- Low iron stores are associated with higher glucose tolerance and might help prevent diabetes (7).
- High iron stores have been linked to cancer.
- High iron stores have been linked to heart disease. Based on an early study, this was
believed to be a strong link for a number of years. Now that more evidence has come in, the link
appears to be only in cases of very high iron storage levels, such as ferritin levels of
greater than 200 µg/l (vegans' ferritin levels are rarely above 100 µg/l).
As of 2010, this theory has lost almost all ground, see:
- Wood RJ. The iron-heart disease connection: is it dead or just hiding? Ageing Res Rev. 2004 Jul;3(3):355-67. (Link)
- Sun Q, Ma J, Rifai N, Franco OH, Rexrode KM, Hu FB. Excessive body iron stores are not associated with risk of coronary heart disease in women. J Nutr. 2008 Dec;138(12):2436-41. (Link)
- Zegrean M. Association of body iron stores with development of cardiovascular disease in the adult population: a systematic review of the literature. Can J Cardiovasc Nurs. 2009;19(1):26-32. (Link)
Hemochromatosis is a disease of unhealthfully high iron absorption. Its most serious, homozygous form occurs in about 1 in 100 blacks and 1 in 200 nonblacks. Its less serious, heterozygous form occurs in 30% of blacks and 12% of nonblacks (4). Most affected people do not know they have the disease (4). People with hemochromatosis are at risk for cirrhosis (4), liver cancer (1), and other diseases. Alcoholic cirrhosis, other liver diseases, iron-loading abnormalities, and other rare diseases can also cause iron overload (1).
Because of the possibility of hemochromatosis, men and postmenopausal women should not actively try to increase iron absorption unless they know they have low iron stores.
Celiac disease is the cause of some cases of unexplained iron deficiency anemia (10). Celiac disease is a condition in which gluten (from wheat, barley, and rye) cause an autoimmune reaction against the intestinal cells. Often, someone has severe diarrhea, vomiting, and other problems. But other times celiac disease goes unnoticed. It occurs in about 1 in 133 people in the U.S.A. (10).
Proton Pump Inhibitors (PPIs) are widely prescribed to treat gastrointestinal diseases. Research has shown that they can cause iron deficiency anemia (16). If you take PPIs and find that you have anemia, talk to your doctor about a possible connection.
|Table 2. Dietary Reference Intake (DRI) for Iron|
|Age (years)||DRI (mg)||Veg DRI (mg)||Upper limita (mg)|
|0 - 6 mos||.27||.27||40|
|7 - 12 mos||11||11||40|
|1 - 3||7||12.6||40|
|4 - 8||10||18||40|
|9 - 13||8||14.4||40|
|aThe Upper Limit for iron
intake is set to prevent gastrointestinal distress
rather than to prevent any possible chronic diseases from iron overload.1
Those who engage in regular, intense exercise may need an additional 30%.5
The new U.S. DRIs for iron distinguish between vegetarians and nonvegetarians (see Table 2). The DRI for vegetarians was determined by increasing the regular DRI by 1.8 times (5). This is controversial because the recommendations were not based on studies of vegetarians, but rather based on vegetarian diets designed to reduce iron absorption. Such a high DRI makes it almost impossible for premenopausal women to meet the DRI without supplements and many vegetarian dietitians do not think it is necessary for most vegetarians to get this much iron.
Iron amounts listed on a nutrition label are based on 18 mg/day. For example, 25% of the Daily Value = .25 x 18 mg = 4.5 mg.
You do not need to worry about iron if you are otherwise healthy and eat a varied vegetarian or vegan diet. If you are concerned about iron absorption you can take steps to increase it by removing coffee, tea, and calcium supplements from meals; adding vitamin C to meals; and increasing legume intake.
If your concerns persist, you should have a doctor measure your iron status. If your iron stores are too low, your doctor might suggest eating meat or taking an iron supplement. If your doctor says you should eat meat, you might want to show him or her this article.
Anemia in meat-eaters is normally treated with large doses of supplemental iron, not with eating more meat. Similarly, vegetarians with IDA do not need to start eating meat but can also be treated with supplemental iron. IDA is normally treated with 100 to 200 mg/day for 4 to 6 months. These large amounts can cause nausea, diarrhea, or constipation, and should only be taken under a doctor's care.
In some women, iron supplementation does not lead to an increase in iron stores. In one study of such women, adding L-lysine (1.5 - 2 g/day for 6 months) to iron supplementation did increase iron stores and decreased hair loss by one half.
I have a vegetarian friend who eats spinach whenever she feels anemic and she says it fixes the problem. Although feeling anemic does not mean someone is anemic, perhaps she is onto something.
In 2002, I was feeling more tired than normal during workouts. I thought maybe I was was anemic, so I had myself checked and I wasn't. I decided to eat more food, put on a few pounds, and my energy returned. However, my serum ferritin levels were on the lower side (52 ng/mL) and in spring of 2008 I decided to start supplementing just to see what would happen. For a few weeks I took a daily tablet of 27 mg iron and 100 mg of vitamin C. I didn't notice any difference in my energy levels and now I only take a tablet once a week or so. My serum ferritin levels were measured at 63 ng/mL in November of 2008.
1. Food and Nutrition Board, Institute of Medicine. 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. Seshadri S, Shah A, Bhade S. Haematologic response of anaemic preschool children to ascorbic acid supplementation. Hum Nutr Appl Nutr. 1985 Apr;39(2):151-4. (Link)
9. Quintaes KD, Farfan JA, Tomazini FM, Morgano MA, de Almeyda Hajisa NM, Neto JT. Mineral Migration and Influence of Meal Preparation in Iron Cookware on the Iron Nutritional Status of Vegetarian Students. Ecology of Food and Nutrition. 2007;46:125-141.
11. Waldmann A, Koschizke JW, Leitzmann C, Hahn A. Dietary iron intake and iron status of German female vegans: results of the German vegan study. Ann Nutr Metab. 2004;48(2):103-8. Epub 2004 Feb 25.
12. Sharma DC, Mathur R. Correction of anemia and iron deficiency in vegetarians by administration of ascorbic acid. Indian J Physiol Pharmacol. 1995 Oct;39(4):403-6. PMID: 8582755. (Abstract only)
13. Siegenberg D, Baynes RD, Bothwell TH, Macfarlane BJ, Lamparelli RD, Car NG, MacPhail P, Schmidt U, Tal A, Mayet F. Ascorbic acid prevents the dose dependent inhibitory effects of polyphenols and phytates on nonheme-iron absorption. Am J Clin Nutr. 1991 Feb;53(2):537-41. PMID: 1989423.
14. Hurrell RF, Reddy M, Cook JD. Inhibition of non-haem iron absorption in man by polyphenolic-containing beverages. Br J Nutr. 1999 Apr;81(4):289-95. PubMed PMID: 10999016. | link
15. Schlesier K, Kühn B, 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 May;46(2):522-27. | link
16. Sarzynski E, Puttarajappa C, Xie Y, Grover M, Laird-Fick H. Association between proton pump inhibitor use and anemia: a retrospective cohort study. Dig Dis Sci. 2011 Aug;56(8):2349-53. (Abstract) | link