The purpose of the Australian Total Diet Study (ATDS) is to estimate the level of dietary exposure (intake) of the Australian population to a range of chemicals including pesticide residues, contaminants, nutrients, additives and other substances that may be found in the food supply. The 22nd ATDS estimated dietary intake of five nutrient trace elements: iodine, selenium, chromium, molybdenum and nickel. Dietary intake was estimated by determining the level of the nutrient in foods by laboratory analysis, and then combining this with the amount of food consumed, as determined in the 1995 National Nutrition Survey (NNS). The dietary intake of the nutrients was assessed against their respective reference health standard for Australian population groups, where available. In order to achieve more accurate dietary intake estimates, the foods examined in the ATDS were prepared to a ‘table ready’ state before they were analysed. As a consequence, both raw and cooked foods were examined.
FSANZ funded and coordinated the 22nd ATDS, while the food regulatory agencies in the State and Territory governments obtained the food samples in their region. The Australian Government Analytical Laboratory (now the National Measurement Institute) carried out sample preparation and analyses.
Ninety-six types of foods, sampled during July/August and November/December 2004, were tested for the five trace elements. The food types selected included both foods that might be expected to show regional variation (regional foods), and foods that were available nationwide and were not expected to show regional variation (national foods). Foods were sampled in each of the States and Territories in Australi a. For each food, between six and ten composite samples were prepared and analysed, with each composite sample consisting of three separate purchases (primary samples).
The dietary intake of each nutrient was estimated using the 1995 National Nutrition Survey (NNS) food consumption data and the level of the nutrient present in each food. Estimated dietary intakes of iodine, selenium, chromium, molybdenum, and nickel were calculated for a range of age–gender groups: infants aged 9 months; girls and boys aged 2-3 years; girls and boys aged 4-8 years; girls and boys aged 9-13 years; adolescent females and males aged 14-18; adult females and males aged 19-29; adult females and males aged 30-49 years; adult females and males aged 50-69 years; and adult females and males aged 70 years and over.
Diets for each individual in the representative age-gender groups from the 1995 NNS were used for intake estimations. For the infants aged 9 months, a theoretical diet was constructed based on an extrapolation of the 2 year old diet from the NNS. The NNS used a 24-hour food recall methodology. A second 24-hour recall was also conducted on 10% of respondents for a non-consecutive day. Standard methodologies were used to estimate an adjusted nutrient (usual) intake based on nutrient intake from the first 24 hour recall (day one), which were then adjusted using nutrient intake information from the second 24 hour recall (day two).