Timing of the introduction of complementary foods in infancy: a randomized controlled trial

Abstract

Objective: To increase knowledge on iron status and growth during the first 6 months of life. We hypothesized that iron status would be better in infants who received complementary foods in addition to breast milk compared with those exclusively breastfed.

Methods: One hundred nineteen healthy term (≥37 weeks) singleton infants were randomly assigned to receive either complementary foods in addition to breast milk from age 4 months (CF) or to exclusive breastfeeding for 6 months (EBF). Dietary data were collected by 3-day weighed food records, and data on iron status and growth were also collected.

Results: One hundred infants (84%) completed the trial. Infants in the CF group had higher mean serum ferritin levels at 6 months (P = .02), which remained significant when adjusted for baseline characteristics. No difference was seen between groups in iron deficiency anemia, iron deficiency, or iron depletion. The average daily energy intake from complementary foods of 5-month-olds in the CF group was 36.8 kJ per kg body weight. Infants in both groups grew at the same rate between 4 and 6 months of age.

Conclusions: In a high-income country, adding a small amount of complementary food in addition to breast milk to infants' diets from 4 months of age does not affect growth rate between 4 and 6 months, but has a small and positive effect on iron status at 6 months. The biological importance of this finding remains to be determined.

FIGURE 1

Trial profile: infants who received complementary foods in addition to breast milk from 4 months compared with infants who were exclusively breastfed for 6 months. ^aOne mother-infant pair was incorrectly instructed to group EBF and was therefore analyzed in group EBF.

FIGURE 2

Box plot of SF divided into quartiles for comparison between groups in each quartile (1 outlier excluded). Mean and SD for each group in each quartile are presented in parentheses: lowest quartile (CF: 17.8 ± 8.4 µg/L vs EBF: 11.9 ± 3.4 µg/L; n = 22; P = .05), second quartile (CF: 49.4 ± 12.7 µg/L vs EBF: 29.9 ± 8.5 µg/L; n = 25; P < .001), third quartile (CF: 83.4 ± 7.8 µg/L vs EBF: 55.5 ± 8.6 µg/L; n = 24; P < .001) and highest quartile (CF: 176.6 ± 45.2 µg/L vs EBF: 117.4 ± 47.5 µg/L; n = 22; P = .007).