The Study
Adverse effects on thyroid of Chinese children exposed to long-term iodine excess: optimal and safe Tolerable Upper Intake Levels of iodine for 7- to 14-y-old children.
This study looked at a bunch of kids and saw that those who ate more iodine were more likely to have big thyroids, but it didn't watch them over time to see if the iodine made their thyroids grow. So we can say iodine and big thyroids are linked, but we can't say iodine definitely caused the problem.
Analysis score
Maximum 44 for a cross-sectional study.
Where the score came from
This study looked at how much iodine is too much for kids, and found that when they eat or drink too much iodine, their thyroid glands (a butterfly-shaped gland in the neck) can get bigger and form goiters.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 544 / 100
Quality score
Snapshots of a population at a single point in time, or descriptions of small groups. Can identify correlations and prevalence, but cannot determine cause and effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1Yes — goiter is a visible, physical sign of thyroid stress, so even if blood tests look normal, a swollen neck means the thyroid is under strain from too much iodine.
- 2Kids who ate 250–299 micrograms of iodine per day had 8.8 times higher risk of goiter; those who ate 300–399 had 5.2 times higher risk.
- 3Thyroid hormone markers like Tg and TSH didn’t reliably change with more iodine.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
The American journal of clinical nutrition
Year
2018
Authors
Wen Chen, Yixin Zhang, Yunmeng Hao, Wei Wang, Long Tan, J. Bian, E. Pearce, M. Zimmermann, Jun Shen, Wanqi Zhang
Related Content
Claims (10)
High intake of iodine from diet increases the production of thyroid antigens and autoantibodies, which intensifies autoimmune thyroid disease.
In children aged 7 to 14, higher iodine intake is associated with a predictable rise in thyroglobulin levels, but the proportion of children with very high thyroglobulin levels stays above 3% regardless of how much iodine they consume, suggesting that this measure cannot reliably identify excess iodine.
In children aged 7 to 14, the rate of elevated thyroid-stimulating hormone stays above 10% whether iodine intake is 200 or 300 micrograms per day, and this pattern does not change consistently with higher iodine levels.
Children aged 7 to 10 should not consume more than 250 micrograms of iodine per day, and children aged 11 to 14 should not consume more than 300 micrograms per day, because higher intakes have been linked to goiter in observational studies, though it is not confirmed that these limits prevent harm.
In children aged 7 to 14, elevated TSH levels are common and stay above 10% regardless of whether iodine intake is 200–300 micrograms per day or higher, indicating that TSH levels alone cannot reliably signal too much iodine in this group.
In children aged 7–14, the size of the thyroid gland and the presence of goiter are better signs of thyroid stress caused by too much iodine over time than blood levels of thyrotropin or thyroglobulin, because they change more consistently with the amount of iodine consumed.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.