The 2016 New Zealand Total Diet Study (2016 NZTDS) was a large-scale food survey undertaken over the 2016 calendar year. The 2016 NZTDS involved the analysis of 1056 composite food samples, with eight samples taken of 132 different food types. The selected food types represent the most commonly consumed foods for the majority of New Zealanders. Changes to the sampled foods in the 2016 NZTDS included the addition of tofu, canned coconut cream and sushi.
Samples were collected quarterly: 62 different regional food types were sampled in January/February and July/August 2016 and 70 different national foods collected in April/May and October/November 2016. Regional foods, those foods that may expect to show regional variation due to local production, were sampled from food retail outlets in Auckland, Christchurch, Napier and Dunedin. National foods, those foods expected to be consistent across the country due to centralised distribution, or resulting from an imported source, were all sampled in Christchurch. All samples were prepared using common food preparation and cooking methods to reflect the way these foods are usually consumed.
All 1056 of the collected samples were analysed for 301 agricultural chemical analytes, six contaminant elements (aluminium, arsenic, cadmium, lead, mercury and tin) and four nutrient elements (iodine, selenium, sodium and zinc). Sub-groupings of foods were analysed for further analytes, including a marker for dithiocarbamate fungicides, 21 herbicides, the contaminants inorganic arsenic and methylmercury, and the nutrient fluoride. All results had been previously published in quarterly reports. Using simulated diets developed for 10 New Zealand population cohorts, including for the first time in the NZTDS two Pacific Island ethnicity adult cohorts, the dietary exposures/ intakes for all of the tested analytes have been estimated. The resulting deterministic exposure/intake estimates have been characterised against health based guidance values or nutrient reference values to establish if there is a public health concern.
None of the estimated dietary exposures to agricultural chemicals represented a risk to health, with the highest dietary exposure reflecting only 2.9% of the respective health based guidance value. The majority of the agricultural chemicals analysed were not detected and therefore calculated to have a zero exposure. A new addition to the NZTDS in 2016 was the assessment of the cumulative dietary exposure to three groupings of agricultural chemicals having common modes of action. The conclusions of this cumulative dietary exposure modelling were that there was not a risk to health, for any of the10 New Zealand population cohorts, for the three chemical groups analysed.
Aluminium has been analysed for the first time in the New Zealand diet in the 2016 NZTDS. Estimates of exposure to aluminium indicate potential concern over younger population cohorts (teenage girls, children, toddlers and infants) exceeding the health based guidance value. The aluminium exposure is largely a result of high concentrations detected in some baked goods (muffins and scones, and cakes and slices).
The form of arsenic of most interest for human exposure is inorganic arsenic. Analysis of inorganic arsenic concentrations in samples with appreciable total arsenic has allowed for refinement in the estimates of dietary exposure for arsenic. Neither inorganic arsenic nor lead have health based guidance values and an alternative method to characterise risk was used. Although the levels of exposure to inorganic arsenic or lead are such that adverse health impacts cannot be ruled out, there is no trend of increase in the diet, and estimated dietary exposure to lead has decreased, compared with reported exposures in the 2009 NZTDS.
Dietary exposure estimates for the other contaminant elements analysed (cadmium, inorganic mercury, methylmercury and tin) are below levels that would represent a health concern.
Dietary intake estimates for the nutrient element iodine show large increases for all of the population cohorts, compared with previous NZTDSs. The increase reflects the mandatory fortification of bread with iodine, through the replacement of non-iodised salt with iodised salt. All population cohorts, apart from infants, are deemed to be at or above the level of dietary iodine intake necessary to avoid dietary deficiency.
The estimated dietary intakes of the nutrients selenium and zinc are also considered to be sufficient to meet nutritional requirements for all of the population cohorts. Zinc dietary intakes appear to have decreased, compared with previous estimates of intakes from the 1990s. In contrast, selenium intakes have seen a small increase over those reported in the 2009 NZTDS, largely due to increased consumption of selenium rich foods in the simulated diets.
Dietary intakes of sodium have seen little change from previously reported values in the 2009 NZTDS and continue to exceed dietary targets and upper levels of intake for all of the population cohorts. An adverse health impact from excess dietary sodium cannot be excluded.
Finally, fluoride concentrations and intakes have been reported from all plant-based foods and beverages. Tea has been identified as a major source of fluoride contribution to adult dietary intakes. Because the analytical method for fluoride only allowed testing of a proportion of the foods sampled in the 2016 NZTDS, a full dietary intake estimate for fluoride cannot be made. As a result, characterising whether dietary needs of fluoride are met, or excessive intake is occurring, in the New Zealand population is not possible.