New Zealand Total Diet Study
The New Zealand Total Diet Study (NZTDS) is a nationwide survey of foods sold in New Zealand. The survey aims to assess New Zealanders' exposure to certain food safety risks.
24 MAY 2018
Final reports released for the 2016 study
The final comprehensive analytical report is available to download. The report includes dietary exposure estimates and a full risk assessment for all specific population groups.Full final report with appendices
Introduction to the study
The New Zealand Total Diet Study (NZTDS) surveys a range of common foods consumed in a typical diet to assess New Zealanders' exposure to certain chemicals, such as agricultural compounds, contaminants, and nutrients.
In the lead up to the 2016 study, MPI consulted on the proposed survey, including the foods and chemicals to be included in the study. Following consultation, MPI released a response to submissions and the final project outline, which provides an overview of the foods and analytes included in the 2016 study.
See the final project outline [PDF, 342 KB]
MPI aims to implement a best practice NZTDS that is consistent with previous surveys. The aim is to strengthen confidence – both domestically and overseas – in the safety of the New Zealand food supply and its monitoring systems.
The last NZTDS was completed in 2009.
Purpose and aims
The NZTDS aims to assess New Zealanders' exposure to certain agricultural compounds, contaminant elements, and nutrients from a range of foods consumed in a typical diet.
Globally, a total diet study (TDS) is considered a critical tool to identify certain food safety risks that might exist. The NZTDS is part of MPI's monitoring and testing programme, which is focused on providing all consumers with the highest levels of assurance on and confidence in the integrity and safety of food consumed in New Zealand.
Information obtained from the NZTDS informs the development and review of New Zealand food standards to ensure that food consumed in New Zealand continues to be safe.
Choosing foods to test
Usually only the most commonly consumed foods – for instance, foods that represent 90% of a population’s intake – are included in a TDS. This means about 130 foods (known as key foods) are included in the survey.
Foods for the NZTDS are selected based on information from the most up to date New Zealand National Nutrition Surveys, which are run by the Ministry of Health. The most recent National Children's Nutrition Survey was completed in 2002, and the National Adult's Nutrition Survey was conducted in 2008/09. Also included in the NZTDS are a small number of foods that are known to be high sources of contaminants.
For the 2016 NZTDS, the key foods to be tested included the most commonly eaten foods as identified in the 2008/09 National Adult's Nutrition Survey. For packaged foods, recent sales data has been used to identify the most popular brands to include in the sampling plan.
Foods are also categorised as either:
- national foods, which are not expected to exhibit any regional variation due to centralised distribution or resulting from an imported source
- regional foods, which are expected to exhibit regional variation due to local production.
To ensure variety, foods are purchased from retail outlets such as supermarkets, greengrocers, butchers, fish shops, takeaways, or cafes. National foods are purchased in one city, while regional foods are purchased from 4 cities.
How food is tested
Food samples are purchased over a calendar year from a number of regions. Before being tested, they are prepared as they would be consumed (for example, bananas are peeled, meat is cooked). Each food is sampled twice over a calendar year to allow for seasonal variations. The sampling and analysis are managed over 4 testing periods, each lasting about 6 weeks.
Many of the analytes in the 2016 NZTDS were included in previous studies, enabling trends to be monitored over time. Additional chemicals have been included in the 2016 study, based on international scientific evidence. The full list of chemicals is included in the final outline document.
Estimating our exposure
Data on levels of certain agricultural compounds, contaminants, and nutrients are combined with information on what people eat for different age-sex groups to give an estimate of dietary exposure to these chemicals. In particular, vulnerable groups (for example infants, children, and adolescents) and groups likely to consume the most food (for example young adult males) are considered a priority.
Using the key foods, 14-day simulated diets are developed for each of these groups in order to estimate dietary exposure to certain chemicals. The population groups for the 2016 NZTDS are included in the final outline document.
Once the level of exposure to chemicals for each of the group has been estimated, these are compared with national/international health-based guidance and standards, such as the Acceptable Daily Intake. This information is used to identify the potential for adverse health effects associated with certain foods.
Results from the 2016 study
Food sampling and testing for NZTDS is done over a calendar year. Throughout that period, results of each sampling quarter have been made public when available. A final comprehensive analytical report including dietary exposure estimates and a full risk assessment for all specific population groups was released on 24 May 2018.
2016 New Zealand Total Diet Study (Q1)
This report presents the results from the first quarterly sampling period (Q1) for the 2016 NZTDS. During this 6-week period, regional samples were purchased in Auckland, Napier, Christchurch, and Dunedin. None of the initial results collected in Q1 indicated a food safety risk.
2016 New Zealand Total Diet Study (Q2)
This report presents the results from the second quarterly sampling period (Q2) for the 2016 NZTDS. During this 6-week period, national samples were purchased in Christchurch. None of the initial results collected in Q2 indicated a food safety risk.
Results – 2016 NZTDS (Q2) [PDF, 582 KB]
2016 New Zealand Total Diet Study (Q3)
This report presents the results from the third quarterly sampling period (Q3) for the 2016 NZTDS. During this 6-week period, regional samples were purchased in Auckland, Napier, Christchurch, and Dunedin.
Results – 2016 NZTDS (Q3) [PDF, 1.1 MB]
2016 New Zealand Total Diet Study (Q4)
This report presents the results from the fourth quarterly sampling period (Q4) for the 2016 NZTDS. During this 6-week period, national samples were purchased in Christchurch. None of the initial results collected in Q4 indicated a food safety risk.
Results – 2016 NZTDS (Q4) [PDF, 1.2 MB]
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. This report presents the results of follow-up testing to see whether these were an isolated event.
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]