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Food Safety Focus (225th Issue, April 2025) – Article 1

Simple Dietary Practice to Getting Sufficient Iodine from a Balanced Diet 

Reported by Dr. Violette LIN, Scientific Officer,
Risk Assessment Section, Centre for Food Safety

Iodine deficiency remains one of the most common micronutrient deficiencies worldwide. This essential micronutrient must be obtained through diet, whether from natural or fortified food. Inadequate iodine intake disrupts thyroid hormone production, leading to a spectrum of adverse health outcomes collectively termed iodine deficiency disorders (IDDs). Notably, recent population-based surveys conducted by Department of Health (DH) revealed that iodine intake was insufficient with mild iodine deficiency for local persons aged 35 or above.

This article provides practical ways for incorporating a variety of iodine-rich foods into our daily diets, aligned with DH’s "Healthy Eating Food Pyramid" (see illustration). By adopting these simple yet effective dietary practices, individuals can make a big difference in their iodine intake, thus reducing the risk of IDDs and promoting lifelong health.

Figure1: Examples of iodine-rich foods on meeting the recommended daily iodine intake of 150 μg/day following a balanced diet based on the "Healthy Eating Food Pyramid".

Why is it Important to Get Sufficient Iodine Every Day?

IDDs can start before birth, posing significant risks to children's mental health and survival. During pregnancy, serious iodine deficiency can even cause stillbirth and congenital abnormalities. Perhaps more insidiously, even mild to moderate deficiency can lead to neurocognitive impairments, diminishing intellectual capacity across the lifespan. Furthermore, Iodine deficiency is the leading preventable cause of thyroid diseases, specifically underactive thyroid (hypothyroidism). Symptoms of hypothyroidism include severe tiredness, feeling cold, slow response, infertility, weight gain, and an enlarged thyroid (goitre), miscarriage and menstrual disorders.

To prevent iodine deficiency, the World Health Organization (WHO) recommends the daily iodine intake as 120 μg for children aged 6 to 12, 150 μg for adolescents and adults, and 250 μg for pregnant or lactating women.

What is the Recommendation for the Public on Iodine Intake?

To review the local and overseas situation and scientific evidences on prevention of iodine deficiency disorders and to make recommendations for local situation for prevention of iodine deficiency disorders, a Working Group on Prevention of Iodine Deficiency Disorders (Working Group) was set up by the DH and Centre for Food Safety (CFS), Food and Environmental Hygiene Department, with representatives from the Hospital Authority, the Hong Kong College of Community Medicine, the Hong Kong College of Family Physicians, the Hong Kong College of Obstetricians and Gynaecologists, the Hong Kong College of Paediatricians, and the Hong Kong College of Physicians.

The Working Group emphasises two key recommendations in its joint recommendations: (i)  consume iodine-rich foods as part of a healthy balanced diet; (ii) use of iodised salt while keeping total salt intake below 5 g daily as recommended by WHO.

Act Now to Boost Your Iodine Intake in the Balanced Diet!

Last month, the CFS reported the iodine content of about 300 foods obtained from local stores. The illustration demonstrates that by adding selected foods into different Food Pyramid food groups could significantly contribute to meeting the iodine needs of 150 μg/day.

Good Foundation Starts from the Food Groups Added with Iodine-Rich Ingredients

While the “Milk and Alternatives” and “Meat, Fish, Eggs and Alternatives” naturally contain iodine, “Grains” serves as a good vehicle for iodine-rich foods. Individuals who limit consumption of the first two food groups could increase iodine intake through adding seaweed-containing vegetarian options. For example,

Additional Strategies for Iodine Optimisation

There are several practical tips can further enhance iodine take. First, for fluid intake, a bowl of Chinese seaweed soup (180 ml) provides 100% daily iodine needs. Preparing soups with seafood and seaweed ingredients can add significant amounts of iodine, e.g., 25 g of dried mussels provides 20% iodine intake. Second, seaweed- and seafood- containing snacks can also supplement dietary iodine easily, as 2 g of seaweed snack and 20 g of dried scallop snack meet 24% and 10% of iodine requirements respectively. Lastly, at the tip of the Pyramid, a teaspoon (5 g) of iodised salt provides 50% to 133% daily iodine needs. These dietary modifications, when implemented consistently, can effectively address iodine insufficiency while maintaining nutritional balance. For comprehensive iodine content data, readers may refer to the CFS webpage.

 Advice to Consumers