The Vitamin A situation

Vitamin A deficiency is a major global problem, affecting populations in developing areas of more than seventy-five countries where clinical and subclinical conditions have been observed (McLaren, 1986; WHO, 1994). Worldwide, this public health problem involves 2.8 to 3 million children with clinical deficiency and 251 million with subclinical deficiency. Vitamin A affects many physiological systems; it plays an essential role in vision and eye health, and it affects growth and susceptibility to infection (particularly diarrhea and measles) and anemia in children (Sommer et al., 1984; Campos et al., 1987; Chandra and Vyas, 1989). The consequences of vitamin A deficiency include blindness, poor growth, severe infection, and death; its control and prevention are central in child health and survival programs (Wasantwisut and Attig, 1995). The International Conference on Nutrition (WHO/FAO, 1993) pledged the elimination of vitamin A deficiency by the year 2000.

The prevention of vitamin A deficiency at the community and household levels depends on the availability and consumption of vitamin A-rich food from either plant or animal sources, and on the presence of other dietary factors needed for bioavailability, absorption, and metabolism of vitamin A, such as sufficient fat, protein, zinc, and other essential nutrients (Booth et al., 1992). Inadequate intake of the appropriate quantity and quality of food to meet vitamin A requirements affects all members of populations with deficiency, but is most common in infants, young children, and pregnant/lactating women. Extensive reviews of the variety of foods containing vitamin A and the effects of vitamin A deficiency are presented elsewhere, and will not be covered here (see, for example, Sommer, 1982, 1995; Bauerfeind, 1986; West, 1991; Booth et al., 1992; Underwood, 1994).