METHODS FOR THE DETERMINATION OF BIOAVAILABILITY OF TRACE-METALS - A CRITICAL-EVALUATION

Trace elements are essential for a wide range of body functions and diet is the main source of trace elements to meet human's daily requirements. Since most of the trace elements belong to transition group of elements, they possess characteristic chemical properties like low solubility in the alkaline pH of the duodenum, which limit their absorption from the gut. Thus, their bioavailability from foods, which is affected by a number of dietary factors, is an important consideration in trace element nutrition. The bioavailability of trace elements can be determined in vivo by extrinsic tagging of food with a radio isotope of the element, using an animal model or an in vitro model. These methods have been developed and extensively used to determine the bioavailability of food iron. Although some of these methods have been extended to a limited extent to zinc, these have yet to be applied to other trace elements. The methods available for the determination of bioavailability of trace elements, their basis, reliability and sensitivity are critically reviewed. The need for developing appropriate in vitro methods for other trace elements, including both essential and toxic elements has been stressed.