Expert Articles

Did Hong Kong children consume too much iodine in their diet? Or insufficient iodine? Can cooking with sea salt help solve children’s iodine deficiency problem?

Author:  Leslie Chan (Registered Dietitian)

  1. What is iodine as a nutrient? Do we need to eat a lot of it every day?
    Iodine is a trace element. The recommended daily intake for children is only 90 micrograms. However, it plays an important role in the body as a crucial raw material for the production of thyroid hormones. Adequate iodine helps promote children’s growth and increase vitality. Insufficient iodine can make children lose energy, lose interest in learning, and even have a severe impact on brain and intellectual development.
  1. Is it true that children who consume too much iodine can develop “goiter”? Do parents often encounter this situation?
    “Goiter,” or enlargement of the thyroid gland, has both intrinsic and extrinsic factors. Excessive consumption of iodine-rich foods or nutritional supplements, as well as insufficient iodine intake, is only one of the causes of goiter. Viral infections and autoimmune diseases can also cause goiters. Therefore, it cannot be generalized.
  1. Do Hong Kong children have iodine deficiency problems?
    Earlier reports from local medical teams found that although Hong Kong children did not show a significant prevalence of pathological iodine deficiency, the overall blood iodine levels were only “marginally satisfactory” and may not meet the developmental needs of the body. In a small number of cases, severe iodine deficiency affecting intellectual development has been observed.
  1. Where does dietary iodine come from?
    There are two main sources of iodine in the diet. The first is seafood, including fish, shellfish such as shrimp and crab, shellfish such as clams and scallops, and seaweed such as nori and kelp. Another source is naturally iodine-rich sea salt (sea salt) and iodized salt as a supplement.
  1. Will living by the seaside still result in iodine deficiency?
    Traditionally, communities and ethnic groups living by the seaside consume more seafood and sea salt, thus experiencing fewer dietary iodine deficiencies. However, the food supply chain is now more complex, and the majority of children growing up in Hong Kong do not primarily rely on fish and seafood as their main source of food. Parents may also not necessarily use sea salt for cooking, so iodine deficiency in children living in Hong Kong is relatively common.
  1. Can the local government solve iodine deficiency by mandating iodized salt?
    Currently, the sale of salt in Hong Kong does not mandate the addition of iodine. Due to significant differences in daily dietary habits and iodine intake among the population, significantly increasing the iodine content of all salt may increase the risk of excessive iodine intake. Therefore, it is challenging for the authorities to establish a statutory level of iodine content in salt that applies to everyone.
  1. How can parents know if their children have iodine deficiency?
    The iodine levels in the body can be analyzed through blood tests, but this practice is not widespread. If parents notice that their children lack energy, have little interest in activities, lack vitality even during their favourite sports, or if there are signs of iodine deficiency or thyroid function problems, they should first assess the risk of iodine deficiency in their diet and consult a family doctor.
  1. How can parents ensure that their children absorb enough iodine?
    Using Sea salt in moderation to cook is a safe practice for providing a constant source of iodine to the body, especially for families with a preference for a meat-based diet and less seafood consumption. As long as the cooking is not overly salty, the chances of exceeding the recommended levels of sodium and iodine are low. Another method is to encourage the consumption of iodine-rich foods such as seafood and seaweed. Including these foods in children’s diets can help ensure an adequate intake of iodine.
    • Does eating seaweed lead to an iodine overdose?

    Many seaweed snacks are rich in iodine, but as long as they are not consumed daily and the portion size is moderate (1-2 small packs per serving), the risk of excessive iodine intake is low. As for seaweed in sushi, it has similar properties to seaweed snacks. Similarly, as long as sushi choices are diversified and not consumed in excess (e.g., excessive amounts of hand rolls) or frequented daily, the issue of iodine overdose can be avoided. Like managing risks with other food items, having a balanced diet, avoiding food biases, and making diverse food choices and combinations in daily meals are all good methods to ensure nutritional balance and prevent excessive intake of individual nutrients.

Recipe reference:
Mini Rice Balls with Corn and Salmon Flakes (6 servings)
(Suitable for children aged 12 months and above.)

Sushi Pearl Rice, 1 bowl

Corn kernels, 3 tablespoons

Salmon flakes, 3 tablespoons

Sushi vinegar, 2 tablespoons

Sushi seaweed, 1 large sheet


  1. Mix the sushi rice and sushi vinegar together.
  2. Cut the sushi seaweed into 6 equal pieces.
  3. Mix the salmon flakes, corn kernels, and sushi rice together.
  4. Divide the mixture into 6 equal portions and roll them into balls.
  5. Wrap each rice ball with a piece of sushi seaweed.
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Did Hong Kong children consume too much iodine in their diet? Or insufficient iodine? Can cooking with sea salt help solve children's iodine deficiency problem?