Posted: December 1st, 2011 - 2:08pm

The 2009 Total Diet Study (TDS) released today by the Ministry of Agriculture and Forestry (MAF) confirms that the common New Zealand diet poses no food safety concerns from chemical residues or contaminants.
“Results from this comprehensive study provide confidence that New Zealand continues to have one of the safest food supplies in the world,” Acting Policy Manager Cherie Flynn says.
The five-yearly study tests 123 commonly eaten foods for chemical residues, and contaminant and nutrient elements. The study enables MAF to estimate and monitor the dietary exposure across eight age-sex groups. Importantly the data can reveal trends that may influence MAF’s food safety risk management strategies.
For all eight age-gender cohorts in the 2009 TDS, estimated dietary exposures to the 241 agricultural compound residues tested for were all well below their relevant acceptable daily intake (ADI). Ninety-three percent of these dietary exposures were less than 0.1% of the ADI.
Cherie says that because actual concentrations of chemicals are measured in foods after they have been prepared as for normal consumption, the TDS provides the most accurate estimate of dietary exposures to these substances for a country as a whole.
“Although we are getting more residue detections than in the past because more sophisticated testing equipment can pick up residues at levels well below what we’ve been picked up in our previous total diet studies, it is very pleasing to see that the actual levels found are trending down,” Cherie says.
Testing for contaminant elements (lead, mercury, methylmercury, cadmium and arsenic) also did not show any cause for concern.
Levels of lead in our diet are now likely to be as low as reasonably achievable according to the results. Estimated dietary exposures to total mercury and methylmercury were below the respective provisional tolerable weekly intakes set by the World Health Organization (WHO). However, those who eat a lot of certain types of fish that have the highest concentrations of mercury (such as large predatory fish like marlin) have the potential to have significantly higher exposures to methylmercury.
Cadmium dietary exposures were below the provisional tolerable monthly intake also set by WHO.
The results on intakes of nutrients revealed that mean sodium intakes exceeded levels that can lead to adverse health effects in six of the age-sex groups by 116 -148%. Only the diet of 25+ year females was below this level. However their intake was still two to four times the intake necessary for general health.
“On a positive note, although dietary intakes are high, trend data suggests that the intake of sodium in some age-sex groups appears to be slowly decreasing. It’s also important to note the great progress the food industry is making in voluntarily reducing sodium in many of the key food categories that contribute the most to people’s sodium intakes,” Cherie says.
WHO supports total diet studies as one of the most cost-effective means for determining whether people are exposed to potentially unsafe levels of toxic chemicals through food. It encourages all countries to undertake total diet studies as a matter of good public health practice.
The full report can be found online at:
http://www.foodsafety.govt.nz/policy-law/food-monitoring-programmes/total-diet-study/documents.htm
Background:
The 2009 TDS involved sampling 123 different foods which represent the most commonly consumed food items for the majority of New Zealanders. These foods were prepared for eating – for example meat cooked and bananas peeled – before being tested.
The 4,330 different food samples were analysed to determine concentrations of 241 agricultural chemical residues, selected contaminants (arsenic, cadmium, lead, mercury and methylmercury) and nutrient elements (iodine, selenium and sodium). A total of 250,000 individual analyses were carried out on the food samples.
The simulated diets for the study’s eight age-sex groups were developed using the representative foods sampled and analysed. The proportion of each food in the simulated two-week diet was based on actual consumption data.
The 2009 TDS is the seventh to be carried out in New Zealand since the initial study was conducted in 1974/75. It was commissioned by the then New Zealand Food Safety Authority, who contracted the Institute of Environmental Science and Research for technical input and operational management.