Objective To assess the effect of a formula with a composition close to human milk, Nan containing or not a probiotic, Bifidobacterium longum (BL999; Morinaga, Japan), on early life microbiota and immune development as compared to a standard control formula.

Methods Randomized, double blind, controlled trial of 3 groups: control formula (n = 33); Nan: 30/70 Casein/Whey ratio, low proteins (1.8 g/100 Kcal); low phosphate (31 mg/100 Kcal) and high lactose levels (11.1 g/100 Kcal) (n = 30); Nan + BL999 (n = 28) and a reference Breast Fed group (BF, n = 35). Healthy singleton term infants received the study formula for 4 months. Primary outcome was stool bifidobacteria counts (log CFU/g: Median [IQR]) at 2 months of age. Secondary outcome was the analysis of stool IgA levels (μg/mL) at 2 months.

Results Bifidobacteria counts were significantly higher for BF (10[0.9]), Nan (10.0[0.8]) or Nan +BL999 (9.8[1.4]) groups than control (9.2[3.5], p<0.01). Both Nan alone or with BL999 tended to promote higher production of fecal IgA than controls (33[32] and 42[35] vs. 22[17] respectively, p = 0.07), closer to BF (53[37]).

Conclusions These data show that infant formulae Nan with or without BL999 have similar bifidogenic effect than BF. Both Nan +/− BL999 tended to enhance immune functions compared to standard formula.