Outcomes of iodine fortification in New Zealand

In New Zealand, mandatory fortification has resulted in increases in the level of iodine in the food supply (Table 3). While there has been a modest improvement in iodine intakes, the AIHW’s review shows that some population groups continue to be at risk of mild iodine deficiency. However, the data available at the time of the AIHW’s review was from small sub-national surveys. Provisional results from a larger national survey, the 2014/2015 New Zealand Health Survey, have since been published and show that median urinary iodine concentrations for women aged 16–44 (104 µg/L) and adults aged 15 and over (103 µg/L) are within the range for adequate iodine status [1].

Table 3: Key mandatory iodine fortification outcomes in New Zealand
Key monitoring question and measurement Pre-mandatory fortification Post-mandatory fortification Further details Outcome

Has the level of iodine in our food supply increased?
Mean/median iodine level of bread

<2 µg/100 g (mean)

28–49 µg/100 g (median)

The predicted mandatory fortification level was 46 µg/100 g.

 Desired outcome achieved

Are the food industries adequately complying with the mandatory fortification standards?

 Not applicable

Salt manufacturers and bakers have systems in place to ensure compliance.

 

 Desired outcome achieved

Have iodine intakes in the population increased, particularly in women of child-bearing age and young children?
Mean iodine intakes

Women aged 16–44: 99 µg/day
Children aged 5–14: 45 µg/day

Women aged 18–44: 108 µg/day
Children aged 5–14: 93 µg/day (48 µg/day increase)

Iodine intakes for women were higher than at baseline; however, results must be interpreted with caution because different methodologies were used (see Section 4.3).
When developing the fortification requirement, the post-fortification predicted increase was 73 µg/day among women of child-bearing age.
Iodine intakes continue to be insufficient.
Iodine supplementation for pregnant and breastfeeding women continues to be necessary (as expected when developing the fortification requirement).

Women of child-bearing age

Partial achievement
Children aged 5–14

Desired outcome achieved

Proportion of the population with iodine intakes below the estimated average requirement

Women aged 16–44: 68%
Children aged 5–14: 95%

Women aged 18–44: 39%
Children aged 5–14: 21%

 Partial achievement

Has the iodine status of the population improved, particularly in women of child-bearing age and young children?
Median urinary iodine concentration (MUIC)

Women aged 18–44: 48 µg/L
Children aged 8–10: 68 µg/L

Women aged 18–44: 68 µg/L
Children aged 8–10: 113 µg/L

MUIC for women aged 18–44 is indicative of mild iodine deficiency.
MUIC for children aged 8–10 is indicative of iodine adequacy.

Women of child-bearing age

Partial achievement

Children aged 8–10

Desired outcome achieved

Has the iodine status of the population improved?
Iodine status

Refer to information on nutrient status.

Does mandatory iodine fortification result in adverse health effects for the population?
Proportion of the population with iodine intakes above the upper level of intake (UL)

Adults: 0%
Children aged 5–14: <1%

Adults: Not applicable
Children aged 5–14: <1%

No assessment of intakes against the UL was performed for adults post-fortification. As intakes are lower than expected, adults aged 18–64 are not expected to be above the UL.

 Not applicable

Desired outcome achieved
Partial achievementPartial achievement
Not applicable: data did not support an overall assessment or a rating was not appropriate.

µg microgram
EAR estimated average requirement (for more information, see the Nutrient Reference Values for Australia and New Zealand website)
MUIC median urinary iodine concentration
UL upper level of intake (for more information, see the Nutrient Reference Values for Australia and New Zealand website)

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