Oxidative stress in healthy breast fed versus formula fed infants

Abstract

Polyunsaturated fatty acids (PUFA), major substrates for lipid peroxidation, have been associated with enhanced oxidative injury. Infants fed solely on breast milk (BM) and infants fed cow's milk modified formulas (F), differ in amount and composition of dietary fatty acids (FA). A major difference relates to breast milk's content of long chain PUFA [C 20–22] which are highly susceptible to peroxidation. In healthy infants, 13 on BM and 13 on F, plasma lipid peroxidation products were determined using TBAR's method and plasma antioxidant capacity evaluated by cyclic voltammetry (CV). Mean age, weight [expressed as % of 50th percentile for age] and hemoglobin levels did not differ between the two groups. Results of the TBARs assay were expressed as malondialdehyde equivalent content nmol MDA/ml plasma: in BM-fed infants 5.87±0.56 (mean ± s. error) vs. 2.34±0.11 in F-fed infants (p<0.001). CV of plasma samples demonstrated uniform peak potential (330 mV) and similar anodic current (4.82 μA±0.7 vs. 4.91μA±0.9) denoting that type and concentration of antioxidants do not differ between groups. Thus, compared to F-fed infants, BM-fed infants exhibit increased peroxidative injury in presence of similar antioxidant capacity. As BM is the “gold standard” of optimal infant nutrition it is difficult to concede to its potential deleterious effects. Rather, based on observations linking oxygen tension with biological processes of maturation and suggestions that intracellular PUFA scavenge oxygen radicals, it is intriguing to speculate as to the physiological role of oxidants and PUFA in early life.