High iodine intake from water may have adverse effects on children by affecting their thyroid levels and can cause goiters to develop. A recent study published in the American Journal of Clinical Nutrition suggested that with an increased iodine intake, the thyroid volume and total goiter rate also increased.
Iodine intake can be detrimental and onsets other health issues when ingested in an excessive amount, especially in children as their bodies and organs are not fully developed and are sensitive. For instance, water that is excessive in iodine content can affect thyroid size in children and form goiters, an enlargement of the thyroid gland. The higher the iodine content, the more it affects the regulation of hormones and chemicals in the body and causes an imbalance. Due to this, a goiter forms when the thyroid gland produces either too much thyroid hormone or not enough.
Based on similar studies, the safe upper iodine intake concentration in children is not determined. Therefore, a study recently published in the American Journal of Clinical Nutrition investigated the effects of high content of iodine in drinking water and how it related to the thyroid size in children. To assess this, Chen et al. conducted a multistage cross-sectional survey of 2089 children in Shandong, China where none of them had a previous medical history of thyroid problems. The sampling was done in two main cities in Shandong, Dezhou and Liaocheng, because the flow of the Yellow River passing through those two cities had a high iodine content due to the deposit of soil. The children were between the ages of 7-14 years and included 1023 boys and 1066 girls. Chen et al. collected two 24-hour urine samples on two non-consecutive days so that they could determine the 24- hour urinary iodine excretion, then calculated the daily iodine intake. The main measures in this study were the thyroid volume (Tvol), total goiter rate (TGR) and iodine intake. The secondary variables measured were height, weight and body surface area. After collecting the data, SPSS was used to further analyze the data. As a result, it was found that Tvols were higher in boys than girls, however, the TGR, which was 9.7% overall, had no difference between both genders. Additionally, Tvol began to increase in children when iodine intake was greater than 150 µg/d, and the TGR exceeded 5% when daily iodine intake was equal to or greater than 250 µg/d for children aged 7–10 or 300 µg/d for children aged 11–14 years. Another finding was that age, sex and body surface area had no influence on the Tvol. Moreover, both Tvol and TGR increased as iodine intake in children increased and the prevalence of a goiter was also high when excessive amounts of iodine was ingested. In conclusion, it was found that the iodine intake ranges that were safe for children aged 7-10 and 11-14 were 150-249 and 150-299 µg/d, respectively.
This study was very carefully analyzed with very few inaccuracies and was supported using quantitative data. However, the only limitation was that the study did not present thyroid hormones or thyroglobulin to see if there was an association between the thyroid function and the high iodine intake. On the contrary, this study was very beneficial to contribute to lacking research in other studies and on a global level for people ingesting a high intake of iodine, whether from water, salt or seaweed, so they are aware of the health issues it could lead to. This is especially important in places such as China or Japan where the dietary consumption is highly excessive in salt, leading to a higher than usual iodine intake.
Written By: Seema Goolie, BSc