A Review of Studies on the Growth of Infants Fed Infant Formula

Abstract

Growth of infants fed isocaloric infant formulas differing in nutritional content was studied. Twenty-three of 109 randomized clinical trials reported some difference in weight, length, or head circumference between formula groups. Logistic regression demonstrated no relation between enrollment prior to 15 d or duration of observation of 15 wk (parameters specified in regulation), and the finding of a significant difference in a growth outcome. Sample size and year of publication also were not correlated with report of a significant growth difference, even though there was a significant correlation between a growth effect and the reporting of data separately by sex (P = 0.012). The difference in mean weight gain between control and test formula groups was comparable to that between formula-fed and breast-fed infants (1 g/d) and smaller than that between male and female infants (4 g/d). Encouraging alternate study designs with flexible enrollment ages and infants who transition from breastfeeding to formula would provide information on physiologic outcomes and common feeding behaviors, as well as growth.