No difference in urinary iodine concentrations between Boston-area breastfed and formula-fed infants.

BACKGROUND: Thyroid hormone is essential for normal mental and physical development in infancy and childhood and is dependent on adequate iodine intake. During the first few months of life, infants are reliant on breastmilk and/or infant formula as their sole sources of dietary iodine. The iodine status of U.S. infants has not been well studied. METHODS: This was a cross-sectional study of 95 breastfed and/or formula-fed infants less than 3 months of age in the Boston area. We measured iodine content from infants' single spot urine samples and assessed associations with infant feeding type as well as maternal demographic data, salt and multivitamin use, smoking status, and diet. RESULTS: The median infant urine iodine concentration was 197.5 µg/L (range 40-897.5 µg/L). Median infant urine iodine concentrations were similar between infants who were exclusively breastfed (n=39, 203.5 µg/L; range 61.5-395.5 µg/L), formula-fed (n=44, 182.5 µg/L; range 40-897.5 µg/L), and mixed (n=10, 197.8 µg/L; range 123-592.5) (p=0.88). There were no significant correlations of infant urinary iodine with maternal salt or multivitamin use (regularly or in the past 24 hours), active or secondhand cigarette smoke exposures, infant weight, infant length, or recent maternal ingestion of common iodine-containing foods, although the correlations with iodine-containing foods are difficult to accurately determine due to the small sample sizes of these variables. CONCLUSIONS: Both breastfed and formula-fed infants less than 3 months of age in the Boston area were generally iodine sufficient. Larger studies are needed to confirm these observations among infants nationwide and elucidate other factors that may contribute to infant iodine nutrition.

Low iodine content in the diets of hospitalized preterm infants.

CONTEXT: Iodine is critical for normal thyroid hormone synthesis and brain development during infancy, and preterm infants are particularly vulnerable to the effects of both iodine deficiency and excess. Use of iodine-containing skin antiseptics in intensive care nurseries has declined substantially in recent years, but whether the current dietary iodine intake meets the requirement for hospitalized preterm infants is unknown. OBJECTIVE: The aim of the study was to measure the iodine content of enteral and parenteral nutrition products commonly used for hospitalized preterm infants and estimate the daily iodine intake for a hypothetical 1-kg infant. METHODS: We used mass spectrometry to measure the iodine concentration of seven preterm infant formulas, 10 samples of pooled donor human milk, two human milk fortifiers (HMF) and other enteral supplements, and a parenteral amino acid solution and soy-based lipid emulsion. We calculated the iodine provided by typical diets based on 150 ml/kg · d of formula, donor human milk with or without HMF, and parenteral nutrition. RESULTS: Preterm formula provided 16.4-28.5 µg/d of iodine, whereas unfortified donor human milk provided only 5.0-17.6 µg/d. Adding two servings (six packets) of Similac HMF to human milk increased iodine intake by 11.7 µg/d, whereas adding two servings of Enfamil HMF increased iodine intake by only 0.9 µg/d. The other enteral supplements contained almost no iodine, nor did a parenteral nutrition-based diet. CONCLUSIONS: Typical enteral diets for hospitalized preterm infants, particularly those based on donor human milk, provide less than the recommended 30 µg/d of iodine, and parenteral nutrition provides almost no iodine. Additional iodine fortification should be considered.