What is the New Zealand Total Diet Study?
The New Zealand Total Diet Study aims to evaluate the risk to New Zealanders from exposure to certain chemicals such as agricultural chemicals, contaminants, and nutrients in a range of foods most commonly eaten in a typical diet. The food, prepared as it would be consumed (for example, bananas are peeled, and meat is cooked) is then tested for the presence and levels of the chemicals, an estimate of exposure for certain population groups determined, and the risk estimated through comparison against health-based guidance values.
The NZTDS, run every 5 to 7 years, is part of New Zealand Food Safety’s monitoring and testing programme that informs policy decision-making and food standard setting, and provides assurance on the safety of our food supply.
Total diet studies are similarly used globally to identify food safety risks.
2024 New Zealand Total Diet Study
The 2024 NZTDS will focus on infants and toddlers, one of our most vulnerable population groups. Infants and toddlers are at higher risk than other population groups due to the amount of food they consume relative to their body weight, and the often more serious effects of some chemicals on, for example, brain development. In line with previous NZTDS, we propose to include agricultural chemicals, contaminants and nutrients, but also other chemicals of interest, for example from food packaging.
Planning for the 2024 NZTDS began in 2022. Food sampling and testing is planned to commence in early 2024. The study will run over a year. We intend to publish the final results of the study in mid-2026.
We sought your views
The proposed scope and methodology for the NZTDS opened for consultation in November 2023. The last day for submissions was 15 December 2023. The next steps are to analyse the submissions and finalise plans before we begin sampling and testing.
How we choose the foods to test for the Total Diet Study
The NZTDS tests the most commonly consumed foods in the New Zealand diet. Foods selected aim to make up about 90% of the target population's intake.
Foods are selected based on the most up-to-date food consumption information available. For the 2024 NZTDS, we are using data from the First Foods New Zealand and Young Foods New Zealand Studies conducted by the University of Otago.
Foods selected are categorised as either:
- national foods, which are not expected to have any regional variation
- regional foods, which are expected to have regional variation.
To ensure variety, foods are purchased from a range of retail outlets. National foods are purchased in one city, while regional foods are purchased from 2 North Island and 2 South Island cities.
How food is tested
Food samples are taken from a number of regions over 4 quarters of the year. Samples are prepared as they would be consumed. For example, bananas are peeled and meat is cooked. Each food is sampled twice in a calendar year to allow for seasonal variation. The sampling and analysis are managed over 4 testing periods, each lasting up to 6 weeks.
The full list of chemicals proposed to be tested is included in the consultation documentation.
Estimating our chemical and nutrient intake from food
The levels of the chemicals tested are combined with information on what people eat, for different age and gender groups, to give an estimate on the intake of these chemicals in the diet.
The level of intake of chemicals estimated for each of the groups is then compared with health-based guidance values to identify if certain chemicals are a concern in the New Zealand diet. Risks may arise from nutrient levels being too low or contaminant levels being too high.
Follow-up studies carried out after the 2016 New Zealand Total Diet Study
New Zealand Food Safety often carries out follow-up studies to look at any unusual findings from the NZTDS. These look more closely at targeted foods to check if the results we saw are outliers or part of a broader trend.
The 2016 NZTDS found the herbicide clopyralid in potatoes, kumara, and mushrooms. We did follow-up testing to see if this was an isolated event. That testing concluded the residues "may have been an incidental occurrence." You can read about the follow up survey and the findings in our report.
The 2016 NZTDS also found aluminium concentrations higher than expected in certain bakery goods, and this was identified as a potential health concern. New Zealand Food Safety engaged with industry to phase out an aluminium-containing food additive. A follow-up survey found that that use of this additive has now been phased out from use in most product recipes.
Find out more
Results from past studies
2003 and 2004
Who to contact
If you have questions about the New Zealand Total Diet Study, email 2024NZTDS@mpi.govt.nz