The Reduction of Maternal Milk Proteins in Mothers Exposed to Passive Smoking: A Prospective Cohort Study

Background: The number of cigarette smokers in people of all ages and the resulting second hand smokers are increasing worldwide. Smoking at home, work or in public places puts others at risk of exposure to second hand smoke. Objectives: To study the effects of second-hand smoking on breast milk proteins. Patients and Methods: This cohort study was conducted on 45 mothers exposed to second-hand smoke (cases) and 45 non-exposed post-partum mothers (controls) who attended health care centers. Milk samples were collected twice, (5-7 days and 4 months after delivery). Exposure was assessed through questionnaires which measured total levels of milk protein and albumin, and milk cotinine, a major metabolite of nicotine. Results: Cotinine levels in the breast milk of mothers in the exposed group were significantly higher than non-exposed group at baseline and 4 months after delivery (P = 0.001). Milk protein profiles in the non-exposed group were significantly higher 5-7 days after delivery in the non-exposed group, but the albumin profile was not significantly different at 4 months post-partum (P = 0.004). Conclusions: Second-hand smoke affects the levels of breast milk proteins that are essential for infant growth.