Background: The effect of breast-feeding on the concentration of nitric oxide (NO) in milk was investigated in lactating mothers.
Methods: Breast milk specimens were obtained from 45 lactating women after normal delivery on postpartum days 1, 2, 3, 4 and 5. The subjects were divided into three groups: group 1, breast-feeding only; group 2, mixed feeding (breast milk by manual expression and additional formula feeds); and group 3, formula feeding only. Milk NO concentration was measured as the sum of nitrite and nitrate using the Griess reaction.
Results: The highest mean milk NO concentration was on day 4 in all groups, but the peak value in group 3 was significantly lower (P<0.0001) than in other groups. The milk NO concentrations of group 1 were significantly greater than those of groups 2 and 3.
Conclusions: We conclude that breast-feeding increases the concentration of NO in milk.