NEW PHYTATE DATA COLLECTION: IMPLICATIONS FOR NUTRIENT REFERENCE INTAKES FOR MINERALS, PROGRAMMES AND POLICIES

In many low-income countries (LICs) staple diets are often plant-based with unrefined cereals, legumes, and oleaginous seeds providing major energy sources. These plant-based foods contain high levels of phytic acid (myo-inositol hexaphosphate, IP6) and its associated Mg, Ca, and K salts -termed phytates, which serve as a storage form of phosphorus and minerals. Phytate is the major inhibitor of iron and zinc absorption, and to a lesser extent calcium, in plant-based diets, forming insoluble complexes in the gastro-intestinal tract that cannot be digested or absorbed because of the absence of intestinal phytase enzyme in humans. The negative effect of phytate on zinc absorption in adults is much greater than previously estimated, with a minimal ability to adaptively increase zinc absorption from high-phytate diets. FAO/INFOODS in collaboration with the International Zinc Nutrition Consultative Group (IZiNCG) have compiled a new comprehensive global repository of analytical data on the moisture, phytate, and Fe, Zn, Ca content (per 100 g edible portion on a fresh weight basis) of raw and processed plant-based foods. Values for partially dephosphorylated isomers of phytic acid (IP5-IP1) are also included, when available, together with details of analytical methods, biodiversity, origin, and food preparation and processing practices. These data will enable intakes and major food sources of phytate to be calculated from food consumption data in LIC and developed countries. Inclusion of data on dephosphorylated isomers of phytic acid (IP5-IP1) as well as phytic acid (IP6) is important because many plant-based staples in LICs undergo fermentation, germination, or soaking, all practices that can result in enzymatic degradation of phytate to lower inositol phosphates (i.e., IP4-IP1) which have a negligible adverse effect on mineral absorption. For each food, molar ratios of phytate: Fe, Zn, or Ca are also specified, which can provide estimates of the proportion of absorbable zinc or iron from foods and diet types. Diets with phytate-to-zinc molar ratios > 15, between 5 and 15, and < 5 are likely to have poor (~15%), moderate (~30%), or good (~50%) zinc bioavailability, respectively, whereas for iron, much lower molar ratios must be achieved to enhance iron absorption (i.e., phytate-to-iron