High protein intake from meat as complementary food increases growth but not adiposity in breastfed infants: a randomized trial

Abstract

Background: High intake of cow-milk protein in formula-fed infants is associated with higher weight gain and increased adiposity, which have led to recommendations to limit protein intake in later infancy. The impact of protein from meats for breastfed infants during complementary feeding may be different.

Objective: We examined the effect of protein from meat as complementary foods on growth and metabolic profiles of breastfed infants.

Design: This was a secondary analysis from a trial in which exclusively breastfed infants (5-6 mo old from the Denver, CO, metro area) were randomly assigned to receive commercially available pureed meats (Meat group; n = 14) or infant cereal (Cereal group; n = 28) as their primary complementary feedings for ∼ 5 mo. Anthropometric measures and diet records were collected monthly from 5 to 9 mo of age; intakes from complementary feeding and breast milk were assessed at 9 mo of age.

Results: The Meat group had significantly higher protein intake, whereas energy, carbohydrate, and fat intakes from complementary feeding did not differ by group over time. At 9 mo of age, mean (± SEM) intakes of total (complementary feeding plus breast milk) protein were 2.9 ± 0.6 and 1.4 ± 0.4 g · kg(-1) · d(-1), ∼ 17% and ∼ 9% of daily energy intake, for Meat and Cereal groups, respectively (P < 0.001). From 5 to 9 mo of age, the weight-for-age z score (WAZ) and length-for-age z score (LAZ) increased in the Meat group (ΔWAZ: 0.24 ± 0.19; ΔLAZ: 0.14 ± 0.12) and decreased in the Cereal group (ΔWAZ: -0.07 ± 0.17; ΔLAZ: -0.27 ± 0.24) (P-group by time < 0.05). The change in weight-for-length z score did not differ between groups. Total protein intake at 9 mo of age and baseline WAZ were important predictors of changes in the WAZ (R(2) = 0.23, P = 0.01).

Conclusion: In breastfed infants, higher protein intake from meats was associated with greater linear growth and weight gain but without excessive gain in adiposity, suggesting that potential risks of high protein intake may differ between breastfed and formula-fed infants and by the source of protein.

FIGURE 1.

Mean (±SD) longitudinal z scores of anthropometric measures by group. Meat group: n = 14; Cereal group: n = 28. A repeated-measures ANOVA used group (Meat group compared with Cereal group) and time (pre compared with post) as the 2 variables and showed a group-by-time interaction for both the LAZ and WAZ (P < 0.05) as follows: the LAZ decreased in the Cereal group, and the WAZ increased in the Meat group and decreased in the Cereal group. Cereal group, lower-protein group; LAZ, length-for-age z score; Meat group, higher-protein group; WAZ, weight-for-age z score; WLZ, weight-for-length z score.

FIGURE 2.

Mean (±SD) changes in WAZ, LAZ, and WLZ over time (5–9 mo of age) between groups. Meat group: n = 14; Cereal group: n = 28. A 1-factor ANOVA of group and baseline (5 mo of age) LAZs or WAZs as covariates showed that changes in the WAZ and LAZ were both different between groups (P < 0.05). Mean values presented for WAZs and LAZs were adjusted means. Cereal group, lower-protein group. LAZ, length-for-age z score; Meat group, higher-protein group; WAZ, weight-for-age z score; WLZ, weight-for-length z score.