NCD Watch

Impact of Iodine Deficiency on Health

21 Apr 2022 (Thu)

Iodine is an essential micronutrient required for normal thyroid function, growth and development. Persistent low iodine intake will result in iodine deficiency and associated disorders. Children, pregnant and lactating women are particularly vulnerable to iodine deficiency disorders.

Iodine deficiency is the world’s most common cause of preventable mental impairment. Even mild iodine deficiency during pregnancy can have long-term adverse impacts on fetal neurocognition. Studies have shown that compared to children of mothers with adequate iodine status, those of women with inadequate iodine status would be more likely to have lower intelligence and educational assessment scores.

Depending on age and physiological status, the recommended nutrient intake for iodine ranges from 90 micrograms per day (μg/d) for pre-school children 0 to 59 months to 150 μg/d for adults. During pregnancy and lactating, women’s iodine requirements increase substantially to 250 μg/d to ensure adequate supply to the foetus and transfer of iodine to breastmilk.

To assess the iodine status of the three vulnerable groups, namely school-aged children, pregnant women and lactating women in Hong Kong, the Department of Health (DH) commissioned the Chinese University of Hong Kong to conduct the Iodine Survey in 2019. Based on the survey result, the iodine status of school-aged children was classified as “adequate”. For pregnant women taking iodine supplements at an average daily intake of equal to or above 150 μg/d, the iodine status was also classified as “adequate”. However, the iodine status of pregnant women taking iodine supplements at an average intake of less than 150 μg/d and those without supplemented iodine as well as lactating women were classified as “insufficient”.

The Working Group on Prevention of Iodine Deficiency Disorders set up by DH and the Centre for Food Safety of the Food and Environmental Hygiene Department recommends pregnant and lactating women to:-

• take an iodine-containing supplement daily, and they should check the iodine content of the supplement to make sure that they have at least 150 μg iodine each day;
• consume a variety of iodine-rich foods (such as seaweed, kelp, seafood, marine fish, eggs, milk and dairy products) as part of a healthy balanced diet; and
• use appropriate amount of iodised salt instead of ordinary table salt. Pay attention to keep the overall salt intake to less than 5 grams (less than 1 teaspoon) per day.

Source: NCD Watch April 2022