Effect of non-suckling on the pH of breast milk and its possible relationship with breast cancer.

The pH of breast milk was determined in 10 lactating mothers after interrupting suckling from one of the breasts, alternately for 120 hr during the 1st, 12th and the 16th postpartum weeks. The milk from the unsuckled breasts had a slightly higher pH at all three times, being slightly alkaline as compared with the suckled breasts from which the milk was slightly acidic. There were differences also between the three diurnal feeds, the pH being higher in the last diurnal samples. If this temporary experimental stoppage of breast feeding is akin to decline of breast feeding, the changes in the pH of breast milk caused by it may provide clues to the mechanism of the long-suggested possible carcinogenic effect of a fall in the prevalence of breast feeding. An alkaline milieu surrounding epithelial cells causes hyperplasia, cell atypia and a marked increase in mitotic activity, changes which are a prelude to neoplasia. The causative relationship of late age at first birth does not find support in the thesis of the alkaline milieu in the aetiology of breast cancer presented here.