Trace element nutrition in developing countries

Population explosion, poverty, pollution and illiteracy are the major problems that are common in developing countries. Apart from these, the majority of the population living in developing countries face a number of other problems that can influence the dietary intake and bioavailability of trace elements. Those include recurrent respiratory and diarrheal infections, heat and humidity, repeated pregnancies and prolonged nutrition, varied eating habits due to local customs and religion, and constant exposure to parasites. The currently accepted dietary allowances (RDAs) in affluent countries may not be applicable to populations in developing countries. Conventional techniques such as computation from recall methods using standard food tables available in developing countries may not provide adequate information about the true daily intake levels. Only direct methods based on the actual analysis of the food and drinks consumed during a 24-hour period can provide the true intake data. The results of a number of national and international studies conducted by the present authors and a survey of the available literature during the last two decades indicate that the daily dietary intake of a number of essential trace elements including iron, selenium and zinc is not adequate to meet the requirements. A lack of characteristic symptoms and diagnostic techniques is the main reason that a marginal deficiency of trace elements is not detected at an early stage. Moreover, trace element problems as a public health issue have a low priority in most developing countries. At the same time, essential trace element deficiencies and a relatively high exposure to toxic metals such as lead and cadmium are very common in many developing countries. One approach in identifying and treating marginal deficiency of trace elements lies in therapeutic trials. Until very simple, sensitive and specific diagnostic tests are available for routine use for detecting trace element deficiencies at an early stage, strategies for supplementation programs and fortification of staple foods with the trace element in question ought to be recommended for risk groups in developing countries. J. Trace Elem. Exp. Med. 11:197-208, 1998. (C) 1998 Wiley-Liss,Inc.