4364.0.55.008 - Australian Health Survey: Usual Nutrient Intakes, 2011-12  
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IODINE

Iodine is an essential nutrient required for the production of thyroid hormones, important for normal growth and development, particularly of the brain. The major dietary sources of iodine include bread and milk.1 Inadequate amounts of iodine may lead to a range of conditions, including goitres, hypothyroidism, and in severe cases, intellectual disability.2 Since October 2009, food regulations in Australia require that iodine is added to the salt used for making bread, except for organic bread and bread mixes for making bread at home.3

2% of males and 8% of females aged two years and over had inadequate intakes of iodine. Females aged 19 years and over were more than four times as likely as males to have inadequate intakes. In general, the prevalence of inadequate intake of iodine for Australian adults aged 19 years and over (2% of males and 10% of females) was higher than amongst children aged 2-18 years (0.4% of males and 2% of females).

Overall, these results were consistent with the biomedical test results from the 2011-12 National Measures Health Survey (NHMS), where around 1 in 10 Australian (13%) aged 5 years and over had a median urinary iodine concentration (UIC) less than 50 g/L. This is within the World Health Organization recommendation of no more than 20% of the population with a UIC less than 50 g/L. The NHMS results also showed women were more likely to be iodine deficient, with a higher proportion having a UIC less than 50 g/L(16% compared with 10% of men). The prevalence of iodine deficiency was also lowest among young children (5-11 years), with only 6% having iodine levels under 50 g/L compared with around 15% of those aged 35–54 years. For more information on iodine biomedical test results, see Feature Article: Iodine. In making comparisons between the NHMS and the usual nutrient intakes, consideration should be given to the differences in the methods used to measure the prevalence of inadequate iodine intakes, including the potential contribution of intakes of iodised discretionary salt to the results of the NHMS.

Almost one in ten children aged 2-3 years (13% of males and 6% of females) had a usual intake from food exceeding the UL for iodine. The proportion exceeding the UL could potentially be higher if the iodine intake from consuming iodised discretionary salt was included, however this could not be quantified from this survey.

Age-specific ULs for iodine are based on data from adults that are extrapolated to children using reference body weights. The UL for iodine is based on sub-clinical hypothyroidism which is an adaptive response of the thyroid to increased levels of iodine and is reversible.4 In a separate previous evaluation of iodine intake by FSANZ, a detailed toxicological review of the UL was undertaken and FSANZ considered that intakes up to 300 g/day should be well tolerated by young children.5,6 Usual nutrient intakes from this publication were compared with this value of 300 g/day and it was found that less than 1% of 2-3 year olds (both males and females) exceeded it.7

Although it is generally not desirable to exceed a UL, the iodine intakes for young children were below a level at which adverse effects may be observed, though a reduced margin of safety exists.


Proportion of population with inadequate iodine intakes (estimated as % below the EAR), by age



Age (years)
EAR (g)(a)
.
Proportion below EAR (%)(b)
.

Males
Females
2-3
65
0.1
0.5
4-8
65
0.1
0.3
9-13
75
0.3
0.5
14-18
95
0.8
6.4
19-30
100
1.5
11.7
31-50
100
1.6
9.0
51-70
100
3.5
10.5
71 and over
100
4.2
9.2

Source:
(a) National Health and Medical Research Council and New Zealand Ministry of Health, 2006, Nutrient Reference Values for Australia and New Zealand, <http://www.nrv.gov.au/nutrients/iodine>, last accessed 4/2/2015
(b) Australian Health Survey: Usual Nutrient Intakes, 2011-12


For more information on iodine biomedical test results, see Feature article: Iodine.


ENDNOTES

1 Australian Bureau of Statistics, 2014, Australian Health Survey: Nutrition First Results - Foods and Nutrients, 2011-12, 'Table 10: Proportion of Nutrients from food groups', data cube: Excel spreadsheet, cat. no. 4364.0.55.007
2 World Health Organization, UNICEF, ICCIDD, 2007, Assessment of iodine deficiency disorders and monitoring their elimination, <http://www.who.int/nutrition/publications/micronutrients/iodine_deficiency/9789241595827/en/>, last accessed 5/12/2014
3 Food Standards Australia New Zealand, 2012, Iodine fortification, <http://www.foodstandards.gov.au/consumer/nutrition/iodinefort/Pages/default.aspx>, last accessed 05/12/2014
4 National Health and Medical Research Council and New Zealand Ministry of Health, 2006, Nutrient Reference Values for Australia and New Zealand, <https://www.nrv.gov.au/nutrients/iodine>, last accessed 4/2/2015
5 Food Standards Australia New Zealand, 2007, Proposal P1003 Mandatory Iodine Fortification for Australia, Supporting Document 9, Consideration of mandatory fortification with iodine, Safety Assessment and Risk Characterisation Report, December 2007, <http://www.foodstandards.gov.au/code/proposals/documents/P1003%20SD9%20-%20Safety%20Assessment.pdf>, last accessed 20/2/2015
6 Food Standards Australia New Zealand, 2008, Proposal P1003, Consideration of Mandatory Fortification with Iodine for Australia and New Zealand, Supporting Document 10, Dietary Intake Assessment Report, Main Report, April 2008, <http://www.foodstandards.gov.au/code/proposals/documents/P1003%20SD10%20-%20Dietary%20Intake%20Assessment.pdf>, last accessed 20/2/2015
7 Not available from published tables. Derived from full usual intake distribution.