Assessment of trace element status in humans.

Trace elements occur in the body in very small or 'trace' amounts. Deficiencies of essential trace elements produce multiple and diverse clinical signs and symptoms. These may arise from inadequate dietary intake, decreased bioavailability, iatrogenic factors, certain disease states in which decreased absorption, excessive excretion and/or utilization occurs, and physiological states in which trace element requirements are increased and/or body stores are reduced. This review discusses both the static and functional laboratory tests used for the assessment of chromium, copper, selenium, and zinc status in humans, with emphasis on those tests suitable for community use. Static tests measure the total quantity of the trace elements in various accessible tissues and body fluids such as hair, nails, blood or some of its components, and urine; functional tests measure the activity of trace-element-dependent enzymes, or a physiological or behavioural function dependent on a specific trace element. The advantages and limitations of each test are discussed, together with the effects of non-nutritional factors that may confound the interpretation of the results. Interpretive criteria are also given, where possible.