Dietary iodine is critical for brain development in infants. But how much daily iodine is required to maintain healthy development and growth?
Keeping a healthy and balanced nutrition is important, especially for pregnant women and infants. One important dietary element is iodine. Iodine, found in seafood, bread, and iodized salt, is required to produce thyroid hormones. Thyroid hormones control metabolism and are needed for proper bone and brain development. Infants are born with low thyroidal iodine stores, so they depend on their diet to receive the proper amount of iodine. An iodine deficiency early in life can cause hypothyroidism, which can impair neuromotor development, but a steady accumulation of thyroidal iodine stores contributes to healthy childhood development and growth. However, data on daily dietary iodine requirement in infants is limited.
A recently published study in the American Journal of Clinical Nutrition sought to determine the minimum daily intake required to achieve iodine balance in infants. The study, performed between January 2015 and August 2015, included 11 infants (five girls and six boys) between the ages of two and five months old from Zurich, Switzerland.
For this study, the researchers used a randomized, double-blind, dose-response balance study technique. They randomly assigned the participants to one of six possible sequences of administration of three kinds of infant formula milk (IFM). The three kinds of IFM contained low, medium, and high iodine content. The double-blind design means that the participants, investigators, and sponsors of this study were masked to formula assignment. The three IFMs, produced specifically for this study, were contained in identical cans labeled with colour code and did not indicate the type of formula or concentration of iodine. The balanced study technique is a study design used to outline nutrient requirements by evaluating the total nutrient intake and excretion, to allow for calculating nutrient retention and thus the daily intake required.
To assess the daily iodine intake for this study, the researchers required the parents of the infants to record all IFMs consumed by the infant and weigh the formula bottle before and after each feeding. The investigators assessed IFM consumption from the weight of the IFM bottles and the measured iodine concentrations they contained.
To assess the daily iodine excretion, investigators collected and assessed urine and feces from soiled infant diapers and cleaning tissues. Using the iodine intake and iodine excretion values, the researchers calculated the iodine retained to determine the minimum daily intake required to achieve iodine balance.
The findings of this study suggest that infants between the ages of two and five months old require a minimum daily iodine intake of 70 micrograms a day. Iodine intakes below this level may result in iodine depletion and eventually hypothyroidism.
However, the researchers note that further studies are needed to connect iodine intake and iodine status in health and development to evaluate the favorable intake level and the tolerable upper intake level for iodine in infants.
Written By: Jessica Gelar, HBSc