Can food-based strategies help reduce vitamin A and iron deficiencies? : a review of recent evidence

It summarizes the current state of knowledge and identifies lessons learned and research gaps. Vitamin A is available from animal sources in the form of retinol and from dark green, leafy vegetables and yellow and orange non-citrus fruits and vegetables in the form of provitamin A carotenoids. Vitamin A from plant sources is less bioavailable (less readily absorbed by the body) than is the vitamin A coming from animal products. In developing countries, most of the vitamin A consumed comes from plant sources, and then only in a few fruits and vegetables, many of them highly seasonal. Iron can also be obtained from both animal and plant sources. Iron from flesh foods (heme iron) such as meat, fish, and poultry is highly bioavailable compared with iron from plant sources (nonheme iron), largely because nonheme iron is affected by compounds present in plant foods that inhibit iron absorption. The most potent of these inhibitors is phytic acid, which is present in large quantities in most cereals and legumes -- often the main staple foods of the poor. Increasing the availability of foods rich in vitamin A and iron by promoting home gardens and the raising of small animals and fish is a popular approach. Increasingly, food-based strategies combine a variety of intervention components. A key to success appears to be the inclusion of a strong nutrition education and behavior change intervention. Proper processing and storage of plant products in order to retain vitamins and minerals and extend product availability -- through drying, for example -- are other ways to boost consumption of essential nutrients year-round. Cooking in iron pots can increase iron intake. Eating certain combinations of foods together -- such as citrus fruits rich in vitamin C and iron containing cereals and legumes -- helps increase the absorption of iron from plant staples. Conversely, not ingesting substances known to inhibit absorption, such as coffee and tea, may increase the bioavailability of iron from plant sources. Unfortunately, large-scale, community trials documenting the effectiveness of these strategies are surprisingly few. Plant breeding approaches, which hold great promise for combating micronutrient deficiency, are still at an early stage of development, and their efficacy and effectiveness have to be demonstrated. Finally, enormous information gaps still exist concerning the efficacy and the effectiveness of most of the strategies reviewed, even those as popular as home gardening. In the end, the same question posed in reviews published decades ago remains: what can food-based interventions to control vitamin A and iron deficiency really achieve?