Monitoring the iodine status of the Swiss population
The FSVO monitors the iodine status of the Swiss population every five years. The 2020–2022 monitoring shows that schoolchildren receive an adequate supply, but pregnant women do not. The results provide important evidence to inform health policy measures.
Background
Iodine status in Switzerland
Switzerland is geologically low in iodine, which is why table salt is fortified with it. This is the most effective measure for preventing iodine deficiency and ensuring adequate iodine intake in the population. Iodine deficiency can cause various health problems as it causes the body to produce too little thyroid hormone.
The FSVO monitors the iodine status of selected population groups every five years. The main indicator is the urinary iodine concentration – a reliable biomarker of iodine intake. The monitoring was carried out from 2020 to 2022.
Objective of iodine monitoring
The monitoring collects representative data on the current iodine status of schoolchildren and pregnant women in Switzerland. It also looks at:
- the thyroid function of pregnant women
- the proportion of pregnant women who take food supplements containing iodine
- how often iodised salt is used in households
The results allow public health measures to be put in place at an early stage if there are signs of inadequate intake.
Results
The urinary iodine concentration in schoolchildren (n=362) indicates an iodine sufficiency (127 µg/L; an adequate concentration is between 100 and 300 µg/L).
However, in pregnant women (n=473) it indicates a deficiency (97 µg/L; an adequate concentration is between 150 and 500 µg/L).
In comparison with the last survey in 2014, iodine status in children has remained unchanged (137 µg/L in 2015), while in pregnant women it has fallen (140 µg/L in 2015).
All pregnant women have normal thyroid function. Pregnant women who take food supplements containing iodine (47%), have higher levels (88 versus 140 µg/L).
Salt samples from the schoolchildren’s households show that 81% use iodised salt.
Detailed results of the latest iodine monitoring survey from 2020 to 2022 were published in the European Journal of Nutrition in 2023: PubMed (nih.gov): Iodine intake in the Swiss population 100 years after the introduction of iodised salt: a cross-sectional national study in children and pregnant women
Study design
The iodine monitoring is a nationwide, representative cross-sectional study. The children (aged 6 to 12) were recruited through schools and paediatricians who had been informed about the study. Pregnant women were involved through their gynaecologists in practices and maternity clinics.
The study was approved by the cantonal ethics committee of the canton of Zurich, which represents all of Switzerland’s ethics committees. For participating schools, the responsible education and health authorities were informed. Written consent was obtained from the pregnant women and the parents of the schoolchildren, while the children gave their verbal consent. Personal data was treated as confidential and pseudonymised, and participation was voluntary. Between 2020 and 2022, schoolchildren submitted a urine sample, and their weight and height were also measured. The parents or guardians provided information on the type of salt used and on their consumption of iodine-rich foods such as milk and dairy products. In addition, salt samples were collected from the homes of a randomly selected 30% of the children and used for iodine content analysis.
For the pregnant women, urinary iodine concentration and thyroid function markers were determined from dried blood samples.
Stakeholders
The study was funded by the Federal Food Safety and Veterinary Office (contract no. 0714001376). It was conducted by the Laboratory of Human Nutrition at ETH Zurich, the Zurich University Children’s Hospital and Unisanté Lausanne.