Iron

Iron is a mineral that the body uses to make haemoglobin, the protein in red blood cells that carries oxygen, as well as myoglobin in muscle and a number of enzymes. Iron deficiency is the most common nutritional deficiency worldwide and affects people on all types of diet, not only vegans. Vegan diets often contain as much iron as, or more than, omnivorous diets, but the form of iron they contain is absorbed less efficiently.

Heme and non-heme iron

Dietary iron comes in two forms:

• Heme iron is found only in animal flesh (meat, poultry and fish). It is relatively well absorbed.
• Non-heme iron is found in plant foods, fortified foods and supplements, and also makes up part of the iron in animal foods. Its absorption is lower and is strongly affected by other components of a meal.

All the iron in a vegan diet is non-heme. The body regulates non-heme iron absorption according to need: people with low iron stores absorb a greater proportion of the iron they eat.

Recommended intakes

The NIH Office of Dietary Supplements reports the following US Recommended Dietary Allowances, set by the Institute of Medicine (IOM):

Because of the lower bioavailability of non-heme iron, the IOM states that the iron requirement for vegetarians is 1.8 times higher than for people who eat meat. This adjustment is widely cited for vegans as well. Some researchers consider the factor conservative, since the body adapts absorption over time, but it remains the official US guidance. Other countries set different reference values.

Factors affecting absorption

Non-heme iron absorption can be increased or decreased by other foods eaten at the same meal.

Enhancers:

• Vitamin C (ascorbic acid), found in citrus fruits, peppers, tomatoes, broccoli, kiwi fruit and berries, is the best-known enhancer.
• Other organic acids found in fruit and vegetables may also help.
• Soaking, sprouting, fermenting and leavening reduce phytate levels and can improve absorption.

Inhibitors:

• Phytates in whole grains, legumes, nuts and seeds.
• Polyphenols, including tannins in tea and coffee; drinking these between meals rather than with them reduces their effect.
• Calcium, including calcium supplements, taken at the same time as iron-rich meals.

Vegan sources

Good plant sources of iron include:

• lentils, chickpeas, beans and peas;
• tofu and tempeh;
• pumpkin seeds, sesame seeds and tahini, cashews;
• whole grains such as oats, quinoa and wholemeal bread;
• dark green leafy vegetables such as kale and spring greens;
• dried fruit such as apricots and figs;
• iron-fortified breakfast cereals and, in the UK, fortified white flour;
• blackstrap molasses.

Spinach contains iron but also oxalates, which reduce absorption, so it is not as useful a source as its iron content suggests. Cooking acidic foods in cast-iron pans can also add small amounts of iron to meals.

Combining foods

Simple combinations can improve the iron value of meals, for example:

• lentil dal served with tomatoes or a squeeze of lemon;
• fortified cereal with strawberries or orange juice;
• bean chilli with peppers;
• hummus with raw red pepper strips.

Iron status in vegans

Studies have generally found that vegetarians and vegans have lower iron stores (as measured by serum ferritin) than meat eaters, but not necessarily higher rates of iron-deficiency anaemia. People at higher risk of deficiency regardless of diet include menstruating women, pregnant women, infants and toddlers, frequent blood donors and endurance athletes (see vegan athletes).

Symptoms of iron deficiency can include tiredness, shortness of breath, pale skin and reduced concentration. Iron supplements should only be taken on medical advice, because excess iron can be harmful and can cause digestive side effects, and some people have conditions such as haemochromatosis that cause iron overload.

This article is for general information. Individuals should consult a doctor or registered dietitian for personal advice, including before taking iron supplements.

See also

• protein
• zinc
• meal planning
• vegan diet and health