Iodine and selenium status and uptake, and iodine nutritional knowledge of women of childbearing-age in Palmerston North, New Zealand : a thesis presented in partial fulfillment of the requirements for the degree of Master of Science in Human Nutrition at Massey University, Manawatu, New Zealand
Objective: To explore the iodine and selenium status and intakes, and iodine
nutritional knowledge of women of childbearing-age in Palmerston North, New Zealand
(NZ), after the implementation of mandatory fortification of bread with iodine.
Method: Fifty women of childbearing-age (non-pregnant and not breastfeeding) were
interviewed (recruited) for the assessment of dietary intake and nutritional knowledge
using a researcher-led questionnaire, including a semi-quantitative food frequency
questionnaire and 24-hour dietary recall. Fifty 24-hour urine samples were obtained
and total volumes were measured. Iodine and selenium were analysed using the
inductive-coupled plasma mass spectrometry.
Result: The median urinary iodine concentration was 64.7 mcg/l, which represents a
mild iodine deficiency (ID), according to the WHO. Based on the individual iodine
status, 70% of the participants were iodine deficient, categorised as marginal (30%),
mild (30%) and moderate (10%). Iodine intake estimated from urinary iodine excretion
(UIE) showed that 34% did not achieve the Estimated Average Requirement
(EAR)(<100 mcg/day) and 46% met the Recommended Dietary Intake (RDI)(150
mcg/day). The median iodine intake was 129.8 mcg/day, indicating suboptimal intake.
The major contributors to iodine intake were milk (35.6%), bread (24.6%), fish and
seafood (15%) and egg (13.8%). The majority of respondents were unaware of the
mandatory fortification of bread with iodine (70%) and also unaware of the ID problem
in NZ (52%). The median excretion of selenium was 31.6 mcg/day and the intake
estimated from urinary excretion was 57.5 mcg/day, with both values above the safe
range for women (30 mcg/day), according to the WHO. Based on the 24-hour recall,
the majority (70%) had inadequate selenium intake (<50 mcg/day), whilst only 20%
met the RDI intake of 60 mcg/day. There was a moderate correlation between the
urinary selenium excretion and UIE (Spearman’s rank order; r (50)=0.547,p<0.05).
Conclusion: ID is still a problem in this population, although mandatory fortification
has been implemented. However, this study shows improved iodine status and intake
compared to previous studies and it thus signifies the benefits of iodine-fortified bread.
In order to help eliminate ID in NZ, an additional strategy, such as the implementation
of iodine fortification in another food vehicle should be considered.