Formula-fed babies contract gastroenteritis more than breast-fed babies, wh
ich is of concern to mothers who cannot breastfeed or, as with HIV-infected
mothers, are discouraged from breastfeeding. The ability of endogenous bre
astmilk xanthine oxidase to generate the antimicrobial radical nitric oxide
has been measured and its influence on the growth of Escherichia cell and
Salmonella enteritides examined. Breastmilk, but not formula feed, generate
d nitric oxide. Xanthine oxidase activity substantially inhibited the growt
h of both bacteria. An important natural antibiotic system is missing in fo
rmula feeds; the addition of xanthine oxidase may improve formula for use w
hen breastfeeding is not a safe option.