Abstract

The body requires certain levels of essential nutrients, such as zinc, to maintain life. Intake less than the required levels can cause impaired function, disease and death. Every essential nutrient has a unique range of tissue concentration and intake necessary for proper physiological and biochemical functioning. Many criteria have been used to set dietary intake levels for nutrients. For trace elements, however, a limited number of investigative approaches are currently employed by researchers due to inadequate information on individual requirements and intake levels. Further, a clear lack of satisfactory biochemical methods to measure zinc nutritional status continues to hinder formulation of dietary guidelines. Thus, many assumptions have to be made, and large safety margins have to be added to assumed daily requirements in order to compensate for this absence of information. Numerous barriers to a full understanding of what constitutes an adequate dietary recommendation for zinc still exist. Zinc is incompletely absorbed, and this absorption can be greatly influenced by the chemical form in which zinc is bound; interactions with other nutrients also affect absorption. Part three of this five-part review presents the current Canadian recommended nutrient intakes for zinc for various sex and age categories and provides a rationale for the suggested values. The important nutrient interactions that affect the bioavailability of zinc, including those with phytates, copper, cadmium, tin and iron, are discussed.