The optimal time to introduce solid foods to an infant's diet is unknown and highly variable throughout the world. Although retrospective studies have found that infants introduced to solids earlier are heavier than infants introduced to solid foods later in life, it is not clear whether other factors may have played a role in affecting body composition. The aim of this study was to determine, in a randomized trial, whether early introduction of solid foods affects growth or body composition. Infants were recruited prior to 3 months of age and were randomized to early (3-4 mos; EARLY) or late (6 mos; LATE) introduction of solid foods. Infants are currently being followed to 3 years of age. 127 infants have had total body scans using dual energy x-ray absorptiometry (DXA, Hologic QDR1000) performed at 3 & 6 mos for measurement of body composition (fat, lean & bone mass). Three-day diet diaries were also completed. There were no significant differences in body composition at 3 mos between EARLY and LATE. Percent increases between 3 & 6 mos did not differ between EARLY and LATE for weight (26.6 ± 8.9 [SD] and 26.2 ± 8.2%), height (9.9 ± 2.2 and 10.9 ± 2.1%), lean (21.0 ± 8.2 and 18.9 ± 9.9%), or bone mass (33.5 ± 13.0 and 35.7 ± 15.7%). EARLY had a slightly smaller increase in fat mass (33.0 ± 25.6%) compared to LATE (41.5 ± 27.3%: P=0.08). Analysis of diet data showed a decrease in formula with the introduction of solid foods resulting in the substitution, rather than addition, of calories. Therefore, early introduction of solid foods does not result in increased body fat at 6 mos of age, with calories from solid foods replacing, not adding to, calories from formula.

Funded by Gerber Products, Inc.