Trace-element nutrition in health and disease: contributions and problems of analysis.

Most imbalances of trace-element nutrition are characterized by the absence of acute, easily recognizable disease. To diagnose marginal deficiencies or excesses of trace elements, the analyst must use rather sophisticated procedures, and even where an imbalance of trace-element nutrition can be proven, the implications for health are not always evident. Previous attempts to connect deviations of trace-element nutrition with health and disease have suffered from conspicuous gaps in our knowledge; etiologic factors for many chronic disease processes are unknown, with the result that existing hypotheses can be onesided. In addition, the biological roles of many trace elements are hypothetical, at best. Whereas the short-term consequences of extreme underor overexposures are reasonably well-known, it is very difficult to investigate the marginal imbalances and their long-term consequences that are most likely related to existing health problems in man. The rapid development of analytical methodology in the past decade has created a powerful tool for trace-element research. However, these tools can be dangerous if their technical and general limitations are not clearly understood. It is necessary to appreciate these limitations, not only in technology but also with regard to the interpretation of the results, in view of the ever-increasing demands on the analytical chemist. These demands are created by the discovery