A meat- or dairy-based complementary diet leads to distinct growth patterns in formula-fed infants: a randomized controlled trial

Abstract

Background: Protein intake from cow milk-based infant formula has been associated with rapid weight gain and increased adiposity, but the effect of protein from complementary foods has not been prospectively evaluated, and the effect of protein from sources other than formula during complementary feeding is not clear.

Objective: The aim of this study was to directly compare the effect of protein from 2 common complementary food sources, meat and dairy, on infant growth and weight trajectory.

Design: Healthy term, formula-fed infants were recruited from the metro Denver area, matched by sex and race/ethnicity and randomly assigned to a meat or a dairy complementary food group from 5 to 12 mo of age. Total protein intake during this 7-mo intervention was ∼3 g ⋅ kg-1 ⋅ d-1 for both groups. Intakes of infant formula, cereal, fruit, and vegetables were ad libitum. Caregivers also completed 3-d diet records at 5, 10, and 12 mo of age. Anthropometric measures were obtained during monthly home visits, and blood samples were collected at 5 and 12 mo of age.

Results: Sixty-four infants completed the intervention (meat: n = 32; dairy: n = 32). The average total protein intake (mean ± SD) increased from 2.01 ± 0.06 g ⋅ kg-1 ⋅ d-1 at 5 mo to 3.35 ±0.12 g ⋅ kg-1 ⋅ d-1 at 12 mo and did not differ between groups. Over time, weight and weight-for-age z score increased by 0.48 ± 0.07. However, there was a significant group-by-time interaction for both length-for-age z score (LAZ) and weight-for-length z score (WLZ). Post hoc analysis showed that LAZ increased in the meat group (+0.33 ± 0.09; P = 0.001 over time) and decreased in the dairy group (-0.30 ± 0.10; P = 0.0002 over time); WLZ significantly increased in the dairy group (0.76 ± 0.21; P = 0.000002 over time) compared with the meat group (0.30 ± 0.17; P = 0.55 over time). Insulin-like growth factor I and insulin-like growth factor-binding protein 3 both increased over time without group differences.

Conclusions: Protein source may have an important role in regulating growth. In these formula-fed older infants, meat- and dairy-based complementary foods led to distinct growth patterns, especially for length. This trial was registered at www.clinicaltrials.gov as NCT02142647.

Figures

FIGURE 1

CONSORT diagram. CONSORT, CONsolidated Standards Of Reporting Trials.

FIGURE 2

Total protein (A) and energy (B, C) intakes (means ± SDs) at 5, 10, and 12 mo of age. Repeated-measures ANOVA of time and group (meat compared with dairy: n = 32 compared with n = 32). Total protein (A) and total energy (B) intakes increased from baseline to 10 and 12 mo. (A) *Group-by-time interaction, P = 0.66; main effect of time, P < 0.001. (B) *Group-by-time interaction, P = 0.53; main effect of time, P < 0.005. There was no difference in protein intake between 10 and 12 mo or between groups at any time points. (C) Total energy intake did not change over time or differ between groups. Dairy, dairy-based complementary protein group; Meat, meat-based complementary protein group.

FIGURE 3

WAZ (A), LAZ (B), and WLZ (C) at baseline and at 7, 8, 9, 10, 11, and 12 mo of age (mean ± SD). Repeated-measures ANOVA of time and group (Meat compared with Dairy: n = 32 compared with n = 32) with maternal BMI and height as covariates. (A) Group-by-time interaction, P = 0.49. There was a significant main effect of time only (P = 0.0006). (B) Significant group-by-time interaction, P = 0.00001. LAZ differed between groups at 9, 10, 11, and 12 mo of age: *P < 0.05, **P = 0.001. (C) Significant group-by-time interaction, P = 0.015. WLZ differed between groups at 11 and 12 mo of age, *P = 0.03. Dairy, dairy-based complementary protein group; LAZ, length-for-age z score; Meat, meat-based complementary protein group; WAZ, weight-for-age z score; WLZ, weight-for-length z score.