An Infant Formula with Partially Hydrolyzed Whey and Intact Protein Demonstrates Adequate Growth and Safety: A 6-Month Randomized, Triple-Blind, Controlled Trial

Background/Objectives: Evidence suggests that partially hydrolyzed whey protein promotes appropriate infant growth; however, research on its long-term effects, especially in Asia, remains limited. This study set out to evaluate the effects of an infant formula containing partially hydrolyzed whey and intact protein on infant growth and development. Methods: This multicenter, triple-blind, randomized non-inferiority trial enrolled healthy full-term infants (≤14 days old). Participants were randomized (1:1) to receive pHF (n = 78) or SF (n = 70) until 6 months of age, with propensity score-matched exclusively breastfed (BF) infants (n = 70) serving as the reference. The primary outcome was daily weight gain. Linear mixed models assessed the association between feeding type and WHO z-scores over time. Results: Over 6 months, the adjusted mean (SE) daily weight gain (g) was 26.4 (1.27) g/day in BF, 26.0 (1.19) g/day in pHF, and 25.3 (1.27) g/day in the SF group. The adjusted mean difference between pHF and SF was 0.64 g/day (95%CI: −1.55, 2.83), confirming non-inferiority. Growth parameters were comparable between pHF and SF, with WHO z-scores remaining within ±1 SD of reference standards. Compared with pHF, SF was associated with a slower increase in length-for-age z score (LAZ). While there was no difference between the pHF and BF groups, WAZ increased significantly less in SF vs. BF [−0.34 (95%CI: −0.58, −0.10), p = 0.003]. Gastrointestinal disorders occurred more frequently in the SF group than in the BF group, with no significant difference between the pHF and BF groups. Conclusions: An infant formula containing partially hydrolyzed whey and intact protein supported adequate growth and was well tolerated during the first six months of life, with growth trajectories comparable to those of breastfed infants.