In this fact sheet: Structure and function, Iron absorption, Sources of iron, Dietary requirements for iron
Maintaining healthy iron levels is an important aspect of a vegetarian diet. Lack of iron is one of the commonest concerns people have in connection with vegetarian food and health. Iron, however, is present in a wide variety of vegetarian foods and, in fact, even the meat eating population relies far more on these foods for their main iron intake.
Structure and function
Iron is required by the body mainly for the production of haemoglobin, the substance that carries oxygen in the blood and the maintenance of the muscle protein myoglobin. Iron is involved in the production of enzymes involved in energy transfer, digestion and nerve function. The body is very efficient at recycling iron as it renews blood cells, but growing infants, children and women have enhanced needs for iron.
There are two types of iron in the diet, called haem iron and non-haem iron. Haem iron is found in meat and non-haem is found in foods of vegetable origin. Non-haem iron is the main form of dietary iron. Interestingly the general population who eat meat in the UK obtain around a quarter of their iron from meat and fish with around 75% of dietary iron coming from cereals, bread, fruit and vegetables.
Though the body responds to low availability of iron by increasing absorption, iron is not as readily absorbed as some other nutrients. The absorption of iron is affected by the presence of other foods in the gut. Calcium, tannins, phenols (found in chocolate, tea and coffee), proteins, for example in cow’s milk and egg, all have a tendency to hinder the absorption of iron. Phytates (phytic acid) found in grains, bread and pasta also have a similar effect. Vitamin C - ascorbic acid - helps to increase the absorption of iron and, in particular, the non-haem form of iron prevalent in the vegetarian diet. How we combine iron-rich foods with those that contain vitamin C can have a significant effect on iron absorption levels.
Bread provides a source of iron but owing to its wheat content also contains phytates. The normal fermentation process reduces the phytate levels in the finished loaf but sourdough breadmaking in particular is beneficial for iron absorption. Its extra long fermentation time produces a bread which is both highly digestible and with much reduced phytate levels.
The presence of vitamin C in the gut has been shown to increase the absorption of non-haem iron up to two or three fold where phytate-containing foods are also ingested.
Sources of iron
Pulses including chickpeas, lentils, kidney beans and tofu. Sprouted beans and seeds such as aduki beans, alfafa and sunflower seeds. Cereals and products such as breakfast cereals and bread. Green leafy vegetables including spinach, kale and cabbage and also broccoli. Nuts, in particular almonds and cashews. Dried fruit especially apricots, dates and raisins. Date syrup and molasses are good sources of iron. Vitamin C which helps with absorption of iron is present in citrus fruit and juices as well as salad items like sweet peppers, lambs lettuce and tomatoes as well as broccoli and leafy greens.
Dietary requirements for iron (RNI)
Average adult woman (19-50) = 14.8mg per day
Average adult man (19+) = 8.7mg per day