[3 problem vitamins in Latin America].

The list of vitamins recognized as essential in human nutrition is extensive. Only some of them, however, are attributed an important role in public health. The present paper deals with three of these selected because their deficiencies still prevail in important sectors of population in the Latin American Region: vitamin A, vitamin C and vitamin D. For each vitamin the paper discusses the scientific bases for their requirements, as well as pragmatic considerations to be taken into account for the derivation of recommended dietary intakes. Reference is made to the logic of applying the concepts of nutrient density when developing guidelines for the design of diets for the family and the community. Adequate nutrient density means that when a diet is consumed in sufficient amounts to satisfy energy requirements, the needs for essential nutrients are also being met. For the above reasons, the principle of expressing the recommended levels of intake of vitamin A and C per 1,000 kilocalories has been followed. This is not the case with vitamin D which, in view of its special feature of being synthesized endogenously, is not really a vitamin in the strict sense of the term and, therefore, a rational and consistent relationship with the energy of the diet cannot be established.