DH releases Thematic Report on Iodine Status (Population Health Survey 2020-22)

     The Department of Health (DH) today (July 20) released the Thematic Report of Iodine Status (Population Health Survey (PHS) 2020-22), which presents the iodine status of the general population of Hong Kong. The survey revealed that the iodine intake for persons aged 35 or above is insufficient and they are advised to increase their iodine intake to maintain adequate iodine nutrition.

     The PHS 2020-22 is a territory-wide population health survey and was conducted between November 2020 and February 2022. The survey interviewed more than 16 000 land-based non-institutional persons aged 15 or above in Hong Kong, and among them over 2 000 respondents further completed the health examination. Part I and Part II of the PHS 2020-22 were published in last December and in April respectively. The thematic report on iodine status released today analyses the health examination findings on urinary iodine concentration (UIC) and gives an account of the iodine status of the local population.

     The survey found that the median UIC of persons aged 15 to 84 was 91.3 μg/L. The median UIC for females (88.1 μg/L) was lower than that of males (93.7 μg/L). Among different age groups, the median UIC in younger age groups was observed to be higher. The median UIC of persons aged 15 to 34 was 107.5 μg/L, while that of persons aged 35 to 54 and 55 to 84 was 92.7 μg/L and 79.8 μg/L respectively. According to the epidemiological criteria set by the World Health Organization (the cut-off of 100 to199 μg/L for median UIC is classified as adequate iodine intake), iodine intake was insufficient with mild iodine deficiency status for persons aged 35 or above, while persons aged 15 to 34 was classified as having adequate iodine intake.

     A spokesman for the DH emphasised that iodine is an essential micronutrient required for normal thyroid function, growth and development. Throughout the course of life, inadequate dietary intake gives rise to iodine deficiency which may result in goitres and hypothyroidism as well as a spectrum of iodine deficiency disorders including impaired mental functioning.

     Iodised salt and iodine-rich food provide sources for maintaining adequate iodine nutrition. However, the use of iodised salt among local domestic households and consumption of seaweed (a type of iodine-rich food) was not common among respondents according to the survey findings. Only 21.0 per cent of the interviewees reported the use of iodised salt at home and only 8.7 per cent of them reported consuming seaweed at least once per week.

     The abovementioned findings of the PHS 2020-22 are consistent with the previous Iodine Survey conducted in 2019. The survey at that time revealed that the iodine intake of school-aged children was considered adequate, while that of pregnant and lactating women was insufficient (except pregnant women taking iodine-containing supplements at an average daily intake of equal to or above 150 ug/day).

     The DH and the Centre for Food Safety of the Food and Environmental Hygiene Department have jointly set up the Working Group on Prevention of Iodine Deficiency Disorders, 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. After reviewing the key findings of this study and the latest scientific evidence, the Working Group opined that members of the public should increase iodine intake to maintain adequate iodine nutrition and made the following joint recommendations:
 

  1. Consume iodine-rich foods
    • Consume food with more iodine as part of a healthy balanced diet.  Seaweed, kelp, seafood, marine fish, eggs, milk and dairy products are food rich in iodine;
    • When choosing iodine-rich snacks, avoid those which are high in salt or fat content;
  2. Use iodised salt
    • Use iodised salt instead of ordinary table salt, keeping total salt intake below 5 grams (1 teaspoon) per day to lower the risk of raised blood pressure;
    • As iodine content in iodised salt may be affected by humidity, heat and sunlight, iodised salt should be stored in a tight and coloured container and kept in a cool dry place;
    • To minimise loss of iodine through the cooking process, in particular from prolonged boiling and pressure cooking, add iodised salt to food as close to the time of serving as possible;
    • Persons with thyroid problems should seek medical advice regarding use of iodised salt;
  3. Additional measures for pregnant and lactating women
    • Take iodine-containing supplements containing at least 150 μg iodine per day;
    • Seek medical advice if in doubt;
    • Persons with existing medical conditions or thyroid problems should consult healthcare professionals and take supplements as instructed.

     For access to the Thematic Report on Iodine Status and the Joint Recommendation on Iodine Intake for Members of the Public, please visit www.chp.gov.hk/en/features/37474.html.