MJA
MJA

Iodine status of Aboriginal teenagers in the Darwin region before mandatory iodine fortification of bread

Med J Aust 2011; 194 (3): 126-130.

Summary

Objective: To determine the iodine status of participants in the Aboriginal Birth Cohort Study who resided in the Darwin Health Region (DHR) in the “Top End” of the Northern Territory prior to the introduction of mandatory iodine fortification of bread.

Design, setting and participants: Participants in our study had been recruited at birth and were followed up at a mean age of 17.8 years. Spot urine samples were collected and assessed for iodine concentration at a reference laboratory. The median urinary iodine concentration (MUIC) of residents of the DHR was calculated and compared with international criteria for iodine status. Analyses were conducted for subgroups living in urban areas (Darwin–Palmerston) and remote communities (rural with an Aboriginal council). We collected a repeat sample in a subset of participants to explore the impact of within-person variation on the results.

Main outcome measure: MUIC for residents of the DHR.

Results: Urine specimens were provided by 376 participants in the DHR. Overall MUIC was 58 μg/L when weighted to the 2006 Census population. Urban boys had higher values (MUIC = 77 μg/L) than urban and remote-dwelling non-pregnant girls (MUIC = 55 μg/L), but all these groups were classified as mildly iodine deficient. Remote-dwelling boys had the lowest MUIC (47 μg/L, moderate deficiency). Pregnant girls and those with infants aged less than 6 months also had insufficient iodine status. Correction for within-person variation reduced the spread of the population distribution.

Conclusions: Previously, iodine deficiency was thought to occur only in the south-eastern states of Australia. This is the first report of iodine deficiency occurring in residents of the NT. It is also the first study of iodine status in a defined Indigenous population. Future follow-up will reassess iodine status in this group after the introduction of iodine fortification of bread.

Please login with your free MJA account to view this article in full

  • Dorothy E M Mackerras1,2
  • Gurmeet R Singh2
  • Creswell J Eastman3

  • 1 Food Standards Australia New Zealand, Canberra, ACT.
  • 2 Menzies School of Health Research, Institute of Advanced Studies, Charles Darwin University, Darwin, NT.
  • 3 International Council for Control of Iodine Deficiency Disorders, Sydney Medical School, University of Sydney, Sydney, NSW.


Acknowledgements: 

We are grateful to the Aboriginal mothers and their children who agreed to be part of our study. We thank Gary Ma (Institute of Clinical Pathology and Medical Research, Westmead Hospital, Sydney, NSW) for performing the urinary iodine measurements, and Joseph McDonnell of Menzies School of Health Research, Darwin, NT for statistical advice. Gurmeet Singh collected field data and samples with the support of a National Health and Medical Research Council Program Grant.

Competing interests:

We received a grant from the Channel 7 Foundation of South Australia to analyse iodine in our study samples. Creswell Eastman has received payment for travel and other expenses to attend board meetings of the International Council for the Control of Iodine Deficiency Disorders.

  • 1. Li M, Ma G, Guttikonda K, et al. Re-emergence of iodine deficiency in Australia. Asia Pac J Clin Nutr 2001; 10: 200-203.
  • 2. Chan SS, Hams G, Wiley V, et al. Postpartum maternal iodine status and the relationship to neonatal thyroid function. Thyroid 2003; 13: 873-876.
  • 3. Gunton JE, Hams G, Fiegert M, McElduff A. Iodine deficiency in ambulatory participants at a Sydney teaching hospital: is Australia truly iodine replete? Med J Aust 1999; 171: 467-470. <MJA full text>
  • 4. Hamrosi MA, Wallace EM, Riley MD. Iodine status in pregnant women living in Melbourne differs by ethnic group. Asia Pac J Clin Nutr 2005; 14: 27-31.
  • 5. Travers CA, Guttikonda K, Norton CA, et al. Iodine status in pregnant women and their newborns: are our babies at risk of iodine deficiency? Med J Aust 2006; 184: 617-620. <MJA full text>
  • 6. Li M, Eastman CJ, Waite KV, et al. Are Australian children iodine deficient? Results of the Australian National Iodine Nutrition Study. Med J Aust 2006; 184: 165-169. Correction in: Med J Aust 2008; 188: 674. <eMJA full text> <MJA full text>
  • 7. Food Standards Australia New Zealand. Proposal P1003 — mandatory iodine fortification for Australia approval report. 6 Aug 2008. http://www.foodstandards.gov.au/_srcfiles/AppR_P1003_Mandatory_Iodine_Fortification_Aust%20AppR.pdf (accessed Sep 2010).
  • 8. National Health and Medical Research Council. Iodine supplementation for pregnant and breastfeeding women. NHMRC public statement Jan 2010. Canberra: NHMRC, 2010. http://www.nhmrc.gov.au/_files_nhmrc/file/publications/synopses/new45_statement.pdf (accessed Sep 2010).
  • 9. World Health Organization, UNICEF, International Council for the Control of Iodine Deficiency Disorders. Assessment of iodine deficiency disorders and monitoring their elimination. A guide for programme managers. 3rd ed. Geneva: WHO, 2007.
  • 10. Dyer AR, Shipley M, Elliott P. Urinary electrolyte excretion in 24 hours and blood pressure in the INTERSALT Study. I. Estimates of reliability. The INTERSALT Cooperative Research Group. Am J Epidemiol 1994; 139: 927-939.
  • 11. Armstrong BK, White E, Saracci R. Principles of exposure measurement in epidemiology. Oxford: Oxford University Press, 1992.
  • 12. Anderson S, Karmisholt J, Pedersen KM, Laurberg P. Reliability of studies of iodine intake and recommendations for number of samples in groups and in individuals. Br J Nutr 2008; 99: 813-818.
  • 13. Subcommittee on Interpretation and Uses of Dietary Reference Intakes and the Standing Committee on the Scientific Evaluation of Dietary Reference Intakes. Dietary reference intakes: applications in dietary planning. Washington, DC: National Academies Press, 2003.
  • 14. Australian Bureau of Statistics. Technical paper on the National Nutrition Survey: confidentialised unit record file. Canberra: ABS, 1998.
  • 15. Sayers SM, Mackerras D, Singh G, et al. An Australian Aboriginal birth cohort: a unique resource for a life course study of an Indigenous population. A study protocol. BMC Int Health Hum Rights 2003; 3: 1.
  • 16. Sayers S, Singh G, Mackerras D, et al. Australian Aboriginal Birth Cohort study: follow-up processes at 20 years. BMC Int Health Hum Rights 2009; 9: 23.
  • 17. Pino S, Fang, S, Braverman LE. Ammonium persulphate: a safe alternative oxidising reagent for measuring urinary iodine. Clin Chem 1996; 42: 239-243.
  • 18. Ohashi T, Yamaki M, Pandav C, et al. Simple microplate method for determination of urinary iodine. Clin Chem 2000; 46: 529-536.
  • 19. Australian Bureau of Statistics. Population distribution, Aboriginal and Torres Strait Islander Australians, 2006. http://www.ausstats.abs.gov. au/ausstats/subscriber.nsf/0/377284127F 903297CA25733700241AC0/$File/47050_2006.pdf (accessed Dec 2010).
  • 20. Seal JA, Doyle Z, Burgess JR, et al. Iodine status of Tasmanians following voluntary fortification of bread with iodine. Med J Aust 2007; 186: 69-71. <MJA full text>
  • 21. Burgess JR, Seal JA, Stilwell GM, et al. A case for universal salt iodisation to correct iodine deficiency in pregnancy: another salutary lesson from Tasmania. Med J Aust 2007; 186: 574-576. <MJA full text>
  • 22. Charlton KE, Gemming L, Yeatman H, Ma G. Suboptimal iodine status of Australian pregnant women reflects poor knowledge and practices related to iodine nutrition. Nutrition 2010; 26: 963-968.
  • 23. Soldin OP, Soldin SJ, Pezzullo JC. Urinary iodine percentile ranges in the United States. Clin Chim Acta 2003; 328: 185-190.
  • 24. Zimmermann MB. The impact of iodised salt or iodine supplements on iodine status during pregnancy, lactation and infancy. Public Health Nutr 2007; 10: 1584-1595.
  • 25. Nelson M, Black AE, Morris JA, Cole TJ. Between- and within-subject variation in nutrient intake from infancy to old age: estimating the number of days required to rank dietary intakes with desired precision. Am J Clin Nutr 1989; 50: 155-167.
  • 26. Brimblecombe JK, O’Dea K. The role of energy cost in food choices for an Aboriginal population in northern Australia. Med J Aust 2009; 190: 549-551. <MJA full text>

Author

remove_circle_outline Delete Author
add_circle_outline Add Author

Comment
Do you have any competing interests to declare? *

I/we agree to assign copyright to the Medical Journal of Australia and agree to the Conditions of publication *
I/we agree to the Terms of use of the Medical Journal of Australia *
Email me when people comment on this article