Lessons from successful micronutrient programs. Part III: program impact

Micronutrient-deficiency control programs have been greatly extended at the national level in the last 10 to 15 years. However, rigorous evaluations of these are scarce, so that conclusions on impact are tentative and based mainly on indirect evidence. The coverage of vitamin A capsule distribution programs has exceeded 70% in most study countries. In countries implementing national iodized salt programs, the coverage reaches 60% to 90% of households with adequately iodized salt. Of the three micronutrients, coverage of iron tablet supplementation is the least well documented due to inadequate program monitoring systems and population survey data. Supplementation of preschool children 6 to 59 months of age with vitamin A capsules has plausibly contributed to the reduction in clinical vitamin A deficiency and its near-elimination in many countries. The impact of vitamin A capsule supplementation on children's biochemical vitamin A status (serum retinol) in national programs may be less. National data on salt iodization show a consistent relation to reduced prevalence of iodine-deficiency disorder symptoms (goiter); the rates of cretinism and other results of iodine deficiency are almost certainly falling too. The evaluation of the impact of salt iodization programs on biochemical iodine status is limited by a lack of data. Although trials have demonstrated the efficacy of iron supplementation in reducing the prevalence of anemia, the interpretation of national-level data is not so clear. Given the substantial financial and technical commitment required to implement national micronutrient-deficiency control programs, it is vital that investment enable the evaluation of the impact of these programs. It is becoming increasingly important to collect data on subclinical deficiency (e.g., biochemical data) to assess program impact.