Findings of study on dietary iodine intake in Hong Kong adults released

Consumers are advised to consume a variety of high-iodine foods e.g. seaweed, seafood, egg and egg products, milk and milk products based as part of a healthy, balanced diet to ensure sufficient iodine intake, in light of the findings of a risk assessment study released by the Centre for Food Safety (CFS) today (July 13).

The study examined the level of iodine in foods on sale in the local market and assessed the dietary iodine intake of Hong Kong adults.

A spokesman for the CFS said, "On the basis of foods that people frequently consume, the CFS collected a total of 271 samples of 92 food items from 11 food groups at local retail markets and restaurants between February and April 2009 to analyse the iodine levels of the edible parts."

The 11 groups are: cereals and grain products; legumes and vegetables; meat and poultry; egg and egg products; milk and milk products including frozen confections; fish; crustaceans and molluscs; non-alcoholic beverages; condiments and sauces (including non-iodised and iodised table salts); sashimi and sushi; and seaweed.

The spokesman said, "Results showed that the iodine levels of the tested samples ranged from 'not detected' to 2 900 000 microgrammes (μg) per kilogramme (kg) of food.

"For each kg of food, the food group with the richest iodine content was seaweed (with a mean level of 460 000 μg), followed by iodised salt (30 000 μg), crustaceans and molluscs (970 μg), egg and egg products (490 μg), milk and milk products including frozen confections (340 μg), fish (190 μg) and sashimi and sushi (86 μg)."

The food groups with a lower level of iodine were meat and poultry; cereals and grain products; legumes and vegetables; and non-alcoholic beverages.

The spokesman said iodine is an essential micronutrient required for normal thyroid function, growth and development. Both deficiency in and an excess of iodine have adverse consequences on the body through its effect on the thyroid gland.

Deficiency in iodine can cause damage to the developing brain, serious retardation in physical and mental development, and goitre. Pregnant and lactating women, infants and young children are especially susceptible to iodine deficiency disorders (IDD).

Given that IDD represents a worldwide public health problem, the World Health Organization (WHO) has recommended national governments and international agencies to accord it the highest priority.

"The thyroid gland requires a sufficient intake of iodine every day so as to maintain an adequate secretion of thyroid hormones. The WHO recommended a daily iodine intake of 150 μg for adolescents and adults," the spokesman said.

He added that the findings indicated that based on the results of the Hong Kong Population-based Food Consumption Survey 2005-2007, the median dietary iodine intake among adults was estimated to be 44 μg per day.

The findings also showed that based on the dietary reference intakes established by the Chinese Nutrition Society for Chinese adults, 93 per cent of the population had an iodine intake below the Recommended Nutrient Intake (150 μg per day).

"Consumers should follow the WHO's recommendation by taking no more than five grammes of salt (one teaspoon) from all sources every day, and replacing non-iodised salt with iodised salt," he added.

As one finding was that most iodine would dissolve in boiling water during food preparation, the spokesman advised consumers to steam or stir-fry food with little oil, cook crustaceans intact, and add iodised salt just before serving the food so as to retain a maximum amount of iodine in food.

In addition to the above advice, he said that women preparing for pregnancy and pregnant and lactating women should seek advice from health professionals to assess the need to take iodine supplements.

The spokesman encouraged the trade to make iodised salt readily available for the public. When iodising salt, the trade may follow the WHO's recommendation by adding from 20 milligrammes (mg) to 40 mg of iodine per kg of salt. They are also advised to properly indicate on such prepackaged table salt that it has been iodine-fortified, and specify the amount of iodine on the label.

"To get a full picture and enable continued monitoring of the iodine status of the local population (including infants, children, pregnant and lactating women), it is necessary to conduct more surveys in Hong Kong in the future.

"This will include biochemical tests and clinical diagnosis as well as surveys on the dietary iodine intake level," the spokesman said.

Details of the risk assessment study are available on the CFS website www.cfs.gov.hk.

Ends/Wednesday, July 13, 2011
Issued at HKT 14:56