Validity of Body Mass Index as a Measure of Adiposity in Infancy.

OBJECTIVES: To assess the validity of body mass index (BMI) and age- and sex-standardized BMI z-score (BMIZ) as surrogates for adiposity (body fat percentage [BF%], fat mass, and fat mass index [kg/m2]) at 3 time points in infancy (1, 4, and 7 months) and to assess the extent to which the change in BMIZ represents change in adiposity. STUDY DESIGN: We performed a secondary analysis of 447 full-term infants in a previous trial of maternal vitamin D supplementation during lactation. Study staff measured infant anthropometrics and assessed body composition with dual-energy x-ray absorptiometry at 1, 4, and 7 months of age. We calculated Spearman correlations (rs) among BMI, BMIZ, and adiposity at each time point, and between change in BMIZ and change in adiposity between time points. RESULTS: Infants (N = 447) were 52% male, 38% white, 31% black, and 29% Hispanic. The BMIZ was moderately correlated with BF% (rs = 0.43, 0.55, 0.48 at 1, 4, and 7 months of age, respectively). BMIZ correlated more strongly with fat mass and fat mass index, particularly at 4 and 7 months of age (fat mass rs = 0.72-0.76; fat mass index rs = 0.75-0.79). Changes in BMIZ were moderately correlated with adiposity changes from 1 to 4 months of age (rs = 0.44 with BF% change; rs = 0.53 with fat mass change), but only weakly correlated from 4 to 7 months of age (rs = 0.21 with BF% change; rs = 0.27 with fat mass change). CONCLUSIONS: BMIZ is moderately correlated with adiposity in infancy. Changes in BMIZ are a poor indicator of adiposity changes in later infancy. BMI and BMIZ are limited as surrogates for adiposity and especially adiposity changes in infancy. TRIAL REGISTRATION: ClinicalTrials.gov: NCT00412074.

Associations of infant feeding with trajectories of body composition and growth.

Background: The extent to which breastfeeding is protective against later-life obesity is controversial. Little is known about differences in infant body composition between breastfed and formula-fed infants, which may reflect future obesity risk.Objective: We aimed to assess associations of infant feeding with trajectories of growth and body composition from birth to 7 mo in healthy infants.Design: We studied 276 participants from a previous study of maternal vitamin D supplementation during lactation. Mothers used monthly feeding diaries to report the extent of breastfeeding. We measured infants' anthropometrics and used dual-energy X-ray absorptiometry to assess body composition at 1, 4, and 7 mo. We compared changes in infant size (z scores for weight, length, and body mass index [BMI (in kg/m2)]) and body composition (fat and lean mass, body fat percentage) between predominantly breastfed and formula-fed infants, adjusting in linear regression for sex, gestational age, race/ethnicity, maternal BMI, study site, and socioeconomic status.Results: In this study, 214 infants (78%) were predominantly breastfed (median duration: 7 mo) and 62 were exclusively formula fed. Formula-fed infants had lower birth-weight z scores than breastfed infants (-0.22 ± 0.86 and 0.16 ± 0.88, respectively; P < 0.01) but gained more in weight and BMI through 7 mo of age (weight z score difference: 0.37; 95% CI: 0.04, 0.71; BMI z score difference: 0.35; 95% CI: 0, 0.69), with no difference in linear growth (z score difference: 0.05; 95% CI: -0.24, 0.34). Formula-fed infants gained more lean mass (difference: 303 g; 95% CI: 137, 469 g) than breastfed infants, but not fat mass (difference: -42 g; 95% CI: -299, 215 g).Conclusions: Formula-fed infants gained weight more rapidly and out of proportion to linear growth than did predominantly breastfed infants. These differences were attributable to greater accretion of lean mass, rather than fat mass. Any later obesity risk associated with infant feeding does not appear to be explained by differential adiposity gains in infancy.

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.

A comparison of 2 intravenous lipid emulsions: interim analysis of a randomized controlled trial.

OBJECTIVE: To assess the safety and efficacy of a fish oil-based intravenous fat emulsion (FIFE) in reducing the incidence of cholestasis in neonates compared with the traditional soybean oil-based intravenous fat emulsion (SIFE). METHODS: A double-blind randomized controlled trial was conducted. Nineteen neonates were enrolled (10 SIFE; 9 FIFE). Nutrition assessments and laboratory studies were serially obtained for the duration of PN support or until 6 months' corrected gestational age. Neurodevelopmental outcomes were assessed at 6 and 24 months' corrected age. RESULTS: There were no differences between groups in demographic characteristics, with an overall median age of 2 days, gestational age of 36 weeks, and birth weight of 2410 g. There were no differences between groups in baseline laboratory values other than alkaline phosphatase (lower in the FIFE group) or in the duration of parenteral nutrition (PN), amount of enteral intake, or the number of operative procedures. The incidence of cholestasis among enrolled patients was significantly lower than expected, resulting in early study termination and an inability to assess for differences in the incidence of cholestasis. The FIFE was associated with no increased risk of growth impairment, coagulopathy, infectious complications, hypertriglyceridemia, or adverse neurodevelopmental outcomes. No patient developed essential fatty acid deficiency. CONCLUSION: The FIFE at 1 g/kg/d was well tolerated in the neonates recruited for this study. Given the necessary early termination of this study, a follow-up trial with revised eligibility criteria is necessary to determine whether the provision of FIFE decreases the incidence of PN-cholestasis compared with the traditional SIFE.

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.