Potential for increasing the content and bioavailability of Re, Zn and Ca in plants for human nutrition

This paper reviews the possibility and limits for increasing the content an d bioavailability of iron (Fe), zinc (Zn) and calcium (Ca) in edible parts of staple crops, such as cereals, pulses, roots and tubers as a way to comb at mineral deficiencies in human populations. Theoretically, this could be achieved by increasing the total level of Fe, Zn and Ca in the plant foods, while at the same time increasing the concentration of compounds which pro mote their uptake (ascorbic acid), and/or by decreasing the concentration o f compounds which inhibit their absorption (phytic acid or phenolic compoun ds). The content of Zn and Ca in grains and fruits can in some cases be inc reased through soil and/or foliar applications of Zn and Ca fertilisers. Pl ant breeding and genetic engineering techniques, however, have the greatest potential to increase Fe and Zn content in grains, roots and tubers. The p ossibility of enhancing Ca and ascorbic acid content in plant foods by plan t breeding and genetic engineering remained to be explored. The critical fa ctor is to ensure that the extra minerals have an adequate bioavailability for man. Given the important role of phytic acid and polyphenols in plant p hysiology, reducing the levels of these compounds in the edible parts of pl ants does not appear to be wise although introduction of phytases which are active during digestion is an exciting possibility. (C) 2000 Society of Ch emical Industry.