The human adult holds almost 2-3g of zinc and approximately 0.1% of that are replenished daily. Dietary recommendations have been done for healthy individuals based on estimates of bioavailability of zinc. Absence of any chemical, functional, and/or physical signs of deficiency of zinc are supposed to be indicative of adequacy. More detailed data is rarely available. Altering food preferences and availability, new food preparation, preservation along with processing technologies might require re-evaluation of the earlier data. Conventional estimates have suggested that 25% of the worlds population are at risk of zinc deficiency. Many of the affected are poor and they rarely consume foods that are rich in highly bioavailable zinc, whereas surviving on foods rich in inhibitors of zinc absorption and/or contain comparatively small amounts of bioavailable zinc. Among the comparatively rich people, food choice is a foremost factor that can cause risk of zinc deficiency. An extra problem among these rich, is the risk of chronic zinc toxicity, which is caused due to excessive consumption of zinc supplements. High intakes of zinc comparatively to copper can lead to copper deficiency. It is a main challenge that has not been resolved for determined health benefit is the closeness of the recommended dietary allowance (RDA) along with the reference dose (RfD) for safe intake of zinc.

Existing recommendations do not consider the several dietary factors influencing the bioavailability of zinc and copper, and also the possibility of toxicity from zinc supplements. Therefore, the present assumed range between safe and unsafe consumptions of zinc is relatively slight. Presently, evaluation of zinc nutriture is very complex, which involves a number of chemical and functional measurements having limitations in sensitivity and specificity. This method needs to be improved so that zinc deficiency or excess can be detected early. A growing number of associations among diseases and zinc status and seemingly normal statuses of health, in which added zinc could be effective to prevent certain disease conditions are present. Thus, it is concluded that a multidisciplinary approach is essential for further recommendations.

Source: Maret W, Sandstead HH. Zinc requirements and the risks and benefits of zinc supplementation. J Trace Elem Med Biol. 2006;20(1):3-18. doi:10.1016/j.jtemb.2006.01.006