Abstract
Up to 40% of New Zealand (NZ) toddlers have low serum zinc concentrations. This could be a result of low intakes of zinc and high intakes of phytate in the diet. Phytate is a known inhibitor of zinc absorption and is found in foods such as cereals and legumes. Currently, there are no data on the phytate contents of foods in the New Zealand food composition database, FOODfiles; therefore the amount of phytate consumed by toddlers cannot be determined. The aim of this study was to compile phytate values for individual foods (i.e., not mixed dishes) in the NZ food composition database, then use these values to calculate the phytate and zinc intakes of South Island New Zealand toddlers aged 12-24 months.
International research papers investigating the phytate content of foods were identified. To adjust these values specifically for New Zealand foods, various calculations were required. These included adjusting phytate values of foods in the literature when the moisture content of foods in FOODfiles was different to that in the literature, and also converting phytate values per dry weight given in the literature into phytate values per wet weight which was the required format for FOODfiles 2010. As the study aimed to examine phytate intakes of South Island toddlers, additional foods not in FOODfiles 2010 and recipes consumed by the toddlers were also assigned phytate values. The Eating Assessment in Toddlers (EAT) study collected five day weighed food records and were entered into Kai-culator, a dietary assessment programme. The phytate values assigned by the candidate were loaded into Kai-culator so the phytate and zinc intakes of the South Island toddlers participating in the EAT study could be determined.
A total of 2400 foods were assigned a phytate value. The majority of South Island participants in the EAT study were “New Zealand European and Other” (92.3%), with a median energy intake of 3621 kJ/day, a median phytate intake of 325 mg/day, and a median zinc intake of 4.2 mg/day. Fifteen percent of toddlers had inadequate zinc intakes, and calculation of the phytate: zinc molar ratio showed that 5% of South Island toddlers were classified as having diets with low zinc absorption levels. The main sources of phytate in the toddlers’ diets were bakery products (35.5%) and breakfast cereals (21.7%).
These New Zealand toddlers had similar phytate intakes to toddlers in other developed western countries, and most of the toddlers had adequate zinc intakes. Although zinc intakes of NZ toddlers were lower than those from the US, this was likely due to zinc fortification in US breakfast cereals. As no blood samples were collected in the EAT study, serum zinc concentrations could not be determined, so the effect of these zinc and phytate intakes on serum zinc concentrations remains unknown. Until the phytate content of foods in FOODfiles 2010 can be determined through chemical analysis, the values assigned to foods in the current study are the best data available on the phytate contents of foods in the New Zealand food supply.