Introduction The Australian Total Diet Study (ATDS) is a significant national survey that examines levels of nutrients and other chemicals in food and estimates exposure of the population to those chemicals through their diet. In Australia, data on some of the trace elements are limited or not available at all. The intakes of some trace elements may have public health significance for Australia, particularly iodine and selenium, where some population groups are suspected of not meeting recommended intakes.

Objective The main objectives of the study were to:

• obtain data on the levels of the trace elements iodine, selenium, molybdenum, chromium and nickel in the Australian food supply;

• estimate dietary intake for various population groups representative of the mean, 5th and 95th percentile intake for consumers;

• assess nutritional adequacy against Estimated Average Requirement (EAR) or Adequate Intake (AI);

• assess the risks of dietary excess against the Upper Level (UL) or other relevant referenced health standard; and

• identify significant foods contributing to the dietary intake of the trace elements.

Design FSANZ funded and coordinated the 22nd ATDS, and the food regulatory agencies in each of the State and Territory governments assisted by obtaining food samples from their region. The National Measurement Institute was the successful tenderer and carried out sample preparation and analyses.

Ninety-six types of foods, sampled during July and November/December 2004, were tested for the five nutrients. The food types selected included both foods that might show regional variation (regional foods), and foods that were available nationwide and are not expected to show regional variation (national foods). For each food, at least six samples were combined into a composite sample that are prepared to a ‘table ready’ state, then analysed to measure the levels of nutrients.

The dietary intake of each nutrient was estimated using the 1995 NNS food consumption data and the level of nutrient measured in each food. Estimated dietary intakes were calculated for the following 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.

The estimated dietary intake of each nutrient from the Australian diet was compared to the relevant Nutrient Reference Value (NRV) such as the Estimated Average Requirements (EAR) or adequate intake levels (AI) and the upper limit of intake (UL) endorsed by the National Health and Medical Research Council (NHMRC) in 2006.

Outcomes The study reported new trace element concentration data in Australian foods and dietary intake estimates for these trace elements.

Concentration data

Regional variations and differences in levels of trace elements in foods were observed but were minimal. This is important where there is regional variation in foods or where fortification of food is being considered to address low nutrient intakes.

Nutrient intakes and comparison to NRVs

Population group intakes were compared to the appropriate NRV. Findings are summarised as follows:

Iodine

• A proportion of some groups of the Australian population have dietary intakes of iodine below the EAR and there is sufficient justification for further investigation. All children at the 5th percentile of intakes are below the EAR (see Fig 1).

• No concerns about excessive dietary intake among Australian population groups.

Iod

ine

inta

ke (

ug

/day

)

Age and Gender group

0

50

100

150

200

250

300

2 - 3 2 - 3 4 - 8 4 - 8 9 - 13 9 - 13 14 - 18 14 - 18

5th Percentile Mean 95th percentile EAR UL

Male Female Female Female FemaleMale Male Male

Figure 1: 5th percentile, mean and 95th percentile iodine intake (µg/day) in children aged 2-18 years

Selenium

• Majority of the Australian population have dietary intakes approaching or exceeding the EAR.

• There are no public health concerns in relation to nutritional adequacy but it would be desirable for consumers with intakes at the 5th percentile in some age and gender groups to increase their dietary intake to meet the EAR.

• No concerns about excessive dietary intake among Australian population groups

Chromium

• Majority of the Australian population have dietary intakes approaching or exceeding the AI.

• There are no public health concerns in relation to nutritional adequacy but it would be desirable for consumers with intakes at the 5th percentile in some age and gender groups to increase their dietary intake to levels at the AI.

• No concerns about excessive dietary intake among Australians population groups.

Age and Gender groups

5th Percentile Mean 95th percentile EAR UL

19 - 29Male

19 - 29 Female

30 - 49 Male

30-49Female

50 - 69Male

50 - 69Female

70+Male

70+ Female

0

50

100

150

200

Sel

eniu

m in

take

(u

g/d

ay)

250

300

350

400

Figure 2: 5th percentile, mean and 95th percentile selenium intake (µg/day) in adults 19 years and above

Molybdenum

• Majority of the Australian population have dietary intakes well above the EAR and there are no public health concerns in relation to nutritional adequacy.

• No concerns about excessive dietary intake among Australians.

Nickel

• Majority of the Australian population have dietary intakes well above the AI, there are no public health concerns in relation to nutritional adequacy.

• No concerns about excessive dietary intake among Australians.

Major contributors Contribution of specific foods to the dietary intake of nutrients

for different age gender groups were usefully quantified through this study. Selenium sources are found to vary across age groups, as can be seen in Figure 3, milk ceases to be a major selenium source for children after approximately 13 years of age.

0%

10%

20%

30%

40%

50%

Per

cen

tag

e C

on

trib

uti

on

60%

70%

80%

90%

100%

Male Female Male Female Male Female Male Female2-3 yrs 4-8 years 9-13 years 14-18 years

Age (yrs) and gender groups

Chicken b reas t, fillet

Pasta, white

Juice, o range

Bread, all types

Milk, all typesBreakfast cereal,mixed g rain All other foods

Beef steak

Figure 3: Major contributing foods for selenium intake in children aged 2-18 years.

Conclusions • The Total Diet Study method was effective for studying

dietary intake of nutrients for the Australian population.

• Comparing the estimated dietary intakes to the EAR or AI and UL provides useful indications of the nutritional adequacy/excess for different age gender populations.

• Generally Australian intakes appear to be within appropriate ranges for the five trace elements, recognising the limitations of the study.

• This type of study can provide valuable data for possible regulatory action.

StuDy Of DIetary Intake Of traCe eleMentS frOM the auStralIan DIetG Duffy, J Baines – Modelling, Evaluation and Surveillance, Surveillance Food Standards Australia New Zealand

Australia PO Box 7186 Canberra BC ACT 2610 www.foodstandards.gov.auNew Zealand PO Box 10559 The Terrace Wellington 6036 www.foodstandards.govt.nz