Effects of exclusive formula or breast milk feeding on oxidative stress in healthy preterm infants

Background: Compared to formula, breast milk is considered to have superior antioxidant properties and consequently may reduce the occurrence of a number of diseases of prematurity associated with oxidative stress. Aims: To test whether the antioxidant properties of breast milk in healthy premature infants are different to those of formula milk by comparing vitamin E levels in milk and determining the excretion of malondialdehyde (MDA) in urine. Methods: Vitamin E was measured in the breast milk of 20 mothers who had given birth prematurely. Urinary MDA was measured in 10 exclusively breast milk fed and 10 exclusively formula fed healthy preterm infants receiving no vitamin supplements. MDA was measured after derivatisation with 2,4-dinitrophenylhydrazine and consecutive HPLC with UV detection. Results: Urinary MDA concentrations were consistently very low (0.074 + 0.033 μM/mM Cr and 0.078 + 0.026 μM/mM Cr in breast and formula fed infants respectively) and not significantly different between healthy breast milk and formula fed infants. Both breast and formula milk contained satisfactory levels (0.3-3.0 mg/100 ml) of vitamin E. Conclusion: Antioxidant properties of both breast milk and formulae are sufficient to prevent significant lipid peroxidation in healthy premature infants.