(LB01-24-26) Milk Protein Free From A1 β-Casein Shows Higher Protein Efficiency Compared With Casein in the AOAC Official Method

Objectives: To determine the protein efficiency ratio (PER) of the protein component in A1 β-casein-free (A1PF) milk-based infant formula, using casein as the reference protein. The study was conducted in accordance with AOAC Official Method 960.48 to demonstrate the nutritional adequacy of the protein source of an infant formula, i.e., that it is sufficient to support normal growth in accordance with FDA guidelines for a new infant formula notification.

Methods: Randomized controlled study of 20 male Sprague–Dawley rats (aged 25 days) randomly allocated (stratified by weight) to A1PF and casein control (containing ~12% A1-type β-casein w/w) diet groups. The two diets were matched in terms of mineral, vitamin, and protein content, with the only difference being the source of protein. Rats were fed ad libitum for 28 days, during which time anthropometric measurements and gastrointestinal tissue samples were taken. The latter were evaluated post hoc for markers of inflammation and oxidative stress.

Results: Both groups had similar mean body weights at baseline, but by day 28, rats fed the A1PF diet were numerically heavier (change from baseline of 118.3 ± 12.99 g vs 62.9 ± 7.51 g; n.s.), potentially owing to these rats consuming more food (and thus, more protein). The mean experimental PER value for the A1PF group was significantly higher than that for the casein control diet group (3.55 vs 2.41, p < 0.0001). The adjusted PER for the A1PF group was 3.68, which was 147% of the adjusted PER for the casein control group (2.50). Analyses additional to PER requirements revealed that rats fed the A1PF diet showed higher levels of cysteine and glutathione in the small intestine and an increased GSH:GSSG ratio, compared with rats fed the casein control diet. IL-1β, IL-4, and TNF-α were all increased and the anti-inflammatory cytokine IL-10 was decreased, in gastrointestinal tissue samples taken from the casein control group compared with those from rats fed the A1PF diet. Lactase gene and protein levels were also significantly higher in the small intestines of rats fed the A1PF diet.

Conclusions: In rats, the A1PF protein source supported greater weight gain per unit of protein consumed compared with a standardized casein diet containing A1-type β-casein 12% w/w. Additional findings suggest that this may stem from reduced inflammation and higher antioxidant levels.

Funding Sources: The a2 Milk Company