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

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-β) has an important potential role in developing the mucosal immune system in infants. However, little is known about what factors influence TGF-β expression in human milk. We investigated whether the behavioral and psychosocial characteristics of mothers affect breast milk TGF-β levels.

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-β2 levels by ELISA. We took an exploratory approach based on linear and ordered logistic regressions to model TGF-β2 concentrations with their multiple potential determinants.

Mothers with depression or poor self-rated health had higher TGF-β2 concentrations than mothers without depression (odds ratio for a higher TGF-β2 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-β2 levels. Milk gathered between August and October or later in the afternoon (3-4 pm vs. 12-2 pm) contained less TGF-β2.

Depression, as the consequence of psychosocial stress, may be a strong determinant of TGF-β levels in breast milk. Seasonal and daily fluctuations in milk TGF-β2 concentrations warrant further study.