Is variation in total antioxidant capacity of human milk associated with levels of bio-active proteins?

OBJECTIVE: As the antioxidant properties of human milk may be beneficial for very preterm-born infants, it is important to identify the association between total antioxidant capacity (TAC) and bio-active proteins. STUDY DESIGN: Breast milk was prospectively collected (four times) on postpartum days 6 to 8, 13 to 15, 20 to 22 and 27 to 29 from 15 mothers who had delivered between 24 and 31 weeks of gestation. Skimmed milk was assayed to measure TAC and bioactive proteins (lysozyme, lactoferrin, leptin and adiponectin). The association between TAC and levels of bio-active proteins during the first month of lactation was analyzed in a regression model. RESULT: Coefficient of determinations (R-2) revealed an overall effect of bio-active proteins on breast milk TAC (R-2 = 0.635+/- 0.102, P<0.0001). Breast milk leptin, lysozyme and lactoferrin levels were identified as independent factors that significantly predict the concentration of TAC. CONCLUSION: The identified enhancement of the antioxidant capacity of human milk by bio-active proteins that are lacking in commercial formula supports consideration of breast milk as ideal nutrition for preterm-born neonates.