Urbanization of Africans in the North West Province is associated with better micronutrient status: the Transition and Health during Urbanization Study in South Africa

The objective of this study was to assess by dietary and biochemical methods in a cross-sectional study the micronutrient status of a population in transition. The study sample was stratified according to the level of urbanization. Africans, aged 15 to 75 years, were recruited from 37 randomly selected sites throughout the North West Province of South Africa. Fieldworkers measured dietary intakes using a validated food frequency questionnaire and a food portion photo book. The following indicators of micronutrient status were measured: serum ferritin, hemoglobin level, hematocrit, total iron-binding capacity, transferrin saturation, serum retinol, and urinary iodine. More than half of all subjects had intakes of vitamin A, folate, ascorbic acid, zinc, iron, and calcium less than 67% of the recommended dietary allowance. According to the biochemical analyses, 7.2% of the men and 26.9% of the women had serum ferritin concentrations less than 20 μg/L. Only 1.5% of all subjects had serum retinol levels less than 20 μg/dL. Urban subjects had significantly higher mean intakes of vitamin A, vitamin B6, vitamin B12, vitamin C, folate, niacin, iron, and zinc than rural subjects. The median urinary iodine of the rural subjects was 93 μg/L compared with the median of 161 μg/L for the urban subjects. Many rural subjects used noniodated salt in cooking. The subjects living in rural areas ate mostly unfortified starchy foods, whereas urban subjects ate more vegetables, fruit, and brown bread and used iodated salt. Regular intake of nutrient-dense foods and iodated salt should be emphasized in nutrition education. The results indicate the importance of the fortification of staple foods with micronutrients in South Africa.