Iodine is an essential trace element for human health and an integral component of the thyroid hormones. Thyroid hormones regulate normal growth and development, particularly of the brain. Iodine deficiency results in low levels of thyroid hormones that can impair brain development and lower intelligence. Infants have only small iodine stores at birth and are entirely dependent on iodine provided by breast milk or infant formula. However, the exact amount of daily iodine that infants need for healthy development is poorly understood and there is insufficient data to define an Estimated Average Requirement (EAR) for this age group.