Iron
Summary
If you think your iron stores might be low, you can probably increase iron absorption by:
- Avoiding tea and coffee at meals.
- Adding a source of vitamin C 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 and Anemia
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.
- Iron deficiency anemia (IDA) - typically measured by a hemoglobin of less than 120 g/l.
IDA symptoms include pale skin, brittle fingernails, 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.
Meat Iron vs. Plant Iron
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. Below are tables showing iron content of some plant foods as well as the Dietary Reference Intakes for iron.
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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.
Vitamin C aids in iron absorption (the iron and vitamin C must be eaten at the same meal). In one study, vegetarian children with iron deficiency anemia in India (who probably did not have high vitamin C intakes) 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 Vitamin C is found in citrus fruits, strawberries, green leafy vegetables (broccoli, kale, collards, swiss chard, brussel sprouts), bell peppers (yellow, red, and green), and cauliflower.
Calcium supplements, coffee, and black and green tea inhibit iron absorption if eaten at the same time as iron, so avoid them at meals in which you are trying to increase iron absorption.3 I want to emphasize this point because I think many people read this info about coffee and tea, but dismiss it. It is the tannins in coffee and black and green tea that prevent the iron absorption.
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.
Iron Deficiency in Vegetarians
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.
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.
It could also be that some new vegetarians drink more tea and coffee with meals, eat less vitamin C wih meals (though research to date has not linked lower vitamin C intake with ID among Western vegetarians), eat less legumes, or have lower stomach acid, and they are the ones who develop ID or IDA more readily.
Low Iron Stores: Not Necessarily Unhealthy
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 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 greater than 200 mcg/l (vegans' ferritin levels are rarely above 100 mcg/l). For now, the Food and Nutrition Board of the Institute of Medicine says, "This body of evidence does not provide convincing support for a causal relationship between the level of dietary iron intake and the risk for CHD [coronary heart disease]." 1
- High iron stores have been linked to cancer.
Hemochromatosis
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
Hemochromatosis affects men more often than women because women lose iron through menstruation. Because of the possibility of hemochromatosis, men should not actively try to increase iron absorption unless they know they have low iron stores.
Iron Deficiency Anemia Can Be Due to Celiac Disease
Celiac disease is the cause of some cases of unexplained iron deficient 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 goes unnoticed. It occurs in about 1 in 133 people in the U.S.A.10
Recommendations for Iron
The new U.S. DRIs for iron distinguish between vegetarians and nonvegetarians (see Table 2 above). 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 premenstrual 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 * 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.
A few years ago 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.
Vegetarianism Responsible for Iron Deficiency in Britain?
Fears over iron deficiency in children, BBC News, December 9, 2002
"Nutritional experts say they are increasingly worried about iron deficiency among infants. Thousands of infants in the UK have a shortage of iron in their diet, raising the risk of delayed development or behaviour problems.
Research suggests the problem is the most common nutritional disorder in the country, with about a quarter of infants not getting enough iron.
The main cause is the use of cow's milk in babies under one year old, coupled with a reduction in red meat consumption and increase in vegetarianism."
I could find no evidence that an increase in vegetarianism is causing an increase in iron deficiency among U.K. infants. There is evidence for British toddlers (not infants), and the authors state, "[I]ron status was not associated with either iron intake or with consumption of a vegetarian diet."
Footnotes
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.
3. Groff J, Gropper S. Advanced Nutrition and Human Metabolism, 3rd ed. Wadsworth: 2000.
4. Mahan LK, Escott-Stump S. Krause's Food, Nutrition, & Diet Therapy, 10th ed. Philadelphia, PA: W.B. Saunders, Co., 2000.
5. Mangels R. "Update on the New DRI's" Vegetarian Nutrition Update Sum 2001;10(4):1-7.
6. Craig WJ. Iron status of vegetarians. Am J Clin Nutr. 1994 May;59(5 Suppl):1233S-1237S.
7. Hua NW, Stoohs RA, Facchini FS. Low iron status and enhanced insulin sensitivity in lacto-ovo vegetarians. Br J Nutr. 2001 Oct;86(4):515-9.
8. Position of the American Dietetic Association and Dietitians of Canada: Vegetarian Diets J Am Diet Assoc. 2003 Jun;103(6):748-65.
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.
10. Niewinski MM. Advances in celiac disease and gluten-free diet. J Am Diet Assoc. 2008 Apr;108(4):661-72.