Exploring The Effects Of Formula Feeding On Infant Immune Development In China: A Prospective Cohort Study

Background and Objectives: The worldwide exclusive breastfeeding rate is suboptimal and this study aims to evaluate effects on infant immune development of formula feeding. Methods and Study Design: A prospective study including 221 infants fed with breast milk or formula was conducted. At 3-month and 9-month, the concentrations of total immunoglobulin (Ig)G, IgM, IgA, IgG1, IgG2, interleukin (IL)-4, interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha) were measured by using enzyme-linked immunosorbent assay (ELISA). Natural killer (NK) cell activity and lymphocyte transformation testing were conducted. Furthermore, the occurrence of infantile diarrhea, respiratory infections and allergic diseases were questioned. Results: The levels of total IgG (Z=-3.21, p=0.001), IgG1 (Z=-2.12, p=0.034), IFN-gamma (t=-2.09, p=0.039) and NK cell activity (t=-2.14, p=0.034) were significant higher in formula-fed infants compared to breast-fed after 3 months. At 9-month, the levels of total IgG (Z=-4.34, p<0.001), IgA (Z=-2.05, p=0.041) and TNF-alpha (t=-2.10, p=0.037) of formula-fed infants were higher, but the lymphocyte stimulation index (t=2.76, p=0.007) was lower than breast-fed infants. While, no significant differences were found in the incidences of diarrhea and respiratory tract infection (p>0.05). Conclusions: This investigation suggested that formula- and breast-feeding have different contributions to infant immune development, but the formula feeding would not cause significantly increase of diarrhea and respiratory infections.