(de Mota et al., 1990; Grantham-McGregor et al., 1991; Lucas et al., 1990; Osuntokun 1972a; Pollitt and Thompson, 1977; Rush, 1984; Smart, 1986; Stocks et al., 1982).

Onset of nutritional and toxic diseases of the nervous system, which include the tropical myeloneuropathies (Roman et al., 1987), are known to be precipitated by pregnancy and lactation. Wernicke's encephalopathy, caused by thiamine deficiency, is a known complication of severe morning sickness during pregnancy (hyperemesis gravidarum) and anorexia nervosa. Females also appear highly susceptible to effects of thiaminases in seasonal foods, such as those from the worm anaphe venata, commonly eaten in southwestern Nigeria and postulated as an etiological factor in seasonal epidemic ataxia (Ademolekun, 1993; Osuntokun, 1972b).

Folate and iron deficiencies, often associated with pregnancy and lactation, may be important determinants of fetal morbidity and mortality in the Sub-Saharan region. During pregnancy there is a greater requirement for folate because of the increased rate of folate metabolism (McParklin et al., 1993). Folate deficiency is widespread in African women and can contribute to a variety of neuropsychiatric syndromes, including peripheral neuropathy, dementia, and depression. The incidence of neural tube defects caused by folic acid deficiency could be as high as 7 per 1,000 deliveries (Airede, 1992), and may well be increasing in areas where maternal malnutrition has increased and folate deficits are significant. It is now well established that periconceptional folate supplementation could prevent first occurrence of neural tube defects (Czeizel and Dudas, 1992; MRC Vitamin Study Research Group, 1991). There is also greater need for folate in subjects with chronic hemolytic disease, such as hemoglobin sickle-cell disease, which afflicts about 1 percent of the West African population, and malaria.

Iron-deficiency is particularly common in Sub-Saharan Africa, and more common in females than in males. A major cause of iron-deficiency is hookworm infection, which afflicts millions of black Africans, especially in rural areas. Hookworm anemia is often unrecognized as an underlying cause of high maternal morbidity and mortality, apathy and poor health in children, and easy fatigability and impaired working capacity in adults (Pawlowski et al., 1991). Menorrhagia and pregnancy states predispose to iron-deficiency anemia. Other risk factors for iron-deficiency are the growth spurt of adolescence, with the accompanying burden of providing iron for an increased red cell mass and increased hemoglobin concentration; childhood, especially between the ages of 4 months and 3