Maternal psychosocial factors determining the concentrations of transforming growth factor-beta in breast milk

Background: Cytokines in breast milk may play crucial roles in the beneficial effects of breastfeeding in protecting against allergic and infectious diseases in infants. In particular, breast milk-borne transforming growth factor-beta (TGF-beta) has an important potential role in developing the mucosal immune system in infants. However, little is known about what factors influence TGF-beta expression in human milk. We investigated whether the behavioral and psychosocial characteristics of mothers affect breast milk TGF-beta levels. Methods: We conducted a survey of all 139 mothers who were lactating between February and October 2010 in Koshu City, Japan. Participants completed a questionnaire and provided breast milk at the health checkups for their 3-month-old child (N = 129, 93%). Breast milk was assayed for total TGF-beta 2 levels by ELISA. We took an exploratory approach based on linear and ordered logistic regressions to model TGF-beta 2 concentrations with their multiple potential determinants. Results: Mothers with depression or poor self-rated health had higher TGF-beta 2 concentrations than mothers without depression (odds ratio for a higher TGF-beta 2 quartile: 3.11, 95% confidence intervals: 1.03-9.37) or those reporting better health (odds ratio: 2.34, 1.21-4.55). Smoking, drinking alcohol, probiotics supplementation, social support, and maternal history of allergic diseases were not associated with milk TGF-beta 2 levels. Milk gathered between August and October or later in the afternoon (34 pm vs. 122 pm) contained less TGF-beta 2. Conclusion: Depression, as the consequence of psychosocial stress, may be a strong determinant of TGF-beta levels in breast milk. Seasonal and daily fluctuations in milk TGF-beta 2 concentrations warrant further study.