New Zealand Total Diet Study

What is the NZ Total Diet Study?

The New Zealand Total Diet Study (NZTDS) aims to assess New Zealanders' exposure to certain contaminants and nutrients. The NZTDS is part of MPI’s monitoring and testing programme. It looks at a range of foods consumed in a typical diet.

Total diet studies are used globally to identify food safety risks. Results from the New Zealand study are used to inform food standards and ensure that food continues to be safe.

Final report for the 2016 study

The final report from the 2016 study was released in May 2018. The report estimates dietary exposure and risk for all specific population groups.

Full final report with appendices [PDF, 12 MB]

An infographic summarising the results of the study [PDF, 163 KB]

New Zealand Total Diet Study – agreed outline and content [PDF, 342 KB]

Choosing foods to test

The study tests the most common foods in the New Zealand diet. It includes around 130 foods that make up 90% of the population's intake.

Foods are selected based on information from the New Zealand National Nutrition Surveys, which are run by the Ministry of Health.

Nutrition survey – Ministry of Health

A small number of foods that are known to be high sources of contaminants are also included.

Foods are also 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 4 cities.

How food is tested

Food samples are taken from a number of regions. Samples are prepared as they would be consumed (for example, bananas are peeled, meat is cooked). Each food is sampled twice in a calendar year to allow for seasonal variations. The sampling and analysis are managed over 4 testing periods, each lasting about 6 weeks.

The full list of chemicals is included in the final outline document.

Estimating our intake

The levels of the chemicals tested are combined with information on what people eat for different age and gender groups. This gives an estimate of the intake of these chemicals in the diet.

The population groups for the 2016 NZTDS are included in the final outline document.

Once the level of intake to chemicals for each of the groups has been estimated, these are compared with health-based guidance values. This information is used to identify if certain chemicals are a concern in the New Zealand diet. This could be from nutrient levels being too low or contaminant levels being too high.

Follow-up studies

MPI often does 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 NZTDS found the herbicide clopyralid in potatoes, kumara, and mushrooms. A report has the results of follow-up testing to see if this was an isolated event.

Clopyralid residues in potatoes, kumara, and mushrooms [PDF, 439 KB]

The NZTDS found aluminium concentrations which were higher than expected in certain bakery goods. 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 looked at how much the aluminium concentrations had changed.

Aluminium in bakery goods [PDF, 783 KB]