Objectives
The research objectives were to determine is lactating mothers are physiologically different than bottle-feeding mothers in neuroendocrine and immune functions.
Design
The study design was a cross-sectional comparison static design in which mothers who were either fully lactating or never lactating from birth were studied at week 4 postpartum.
Sample
Twenty-nine mothers (18 breast feeders and 11 bottle feeders) recruited from private obstetrical practices and the Health Department were studied cross sectionally at weeks 4 postpartum. The sample had a mean age of 29.3 years, a mean number of 1.6 children, and an income level of $30,000.
Variables Studied
Blood samples were taken and analyzed for cortisol, prolactin, IgA, and several proimmune and proinflammatory cytokines. Mothers completed the Inventory of Small Life Events, the Carr Infection Symptom Checklist, and a demographic form.
Methods
A T cell proliferation assay with conconavalin A was used to measure mitogen response of separated lymphocytes. Frozen sera were saved for analysis over a period of 2 years and all samples were assayed at the same time. Enzyme-linked immunoassays were used to measure hormones and serum cytokines.
Findings
Breast feeders had higher serum levels of IL-2 (4.44 ng/ml) than bottle feeders (.89 ng/ml), a significant difference (t=2.6, p=. 025). They had higher levels of IL-10 (7.04 ng/ml compared to 4.26 ng/ml) but this difference was not significant. Breast feeders had significantly higher serum cortisol (t=2.5, p=. 024), oxytocin, prolactin and serum IgA. IL-2 levels correlated with reports of infection (r=. 882, p=. 002) in breast feeders, although they reported fewer symptoms than bottle feeders. Breast feeders reported less sleep than bottle feeders (t=2.23, p=. 04), and this was correlated with IL-10 levels (r=. 76, p=. 01). Stressors experienced included negative events with family members, and this score was correlated with IL-2 (t=. 833, p=. 005). IL-2 was also related to the mitogen proliferation response (t=. 769, p=. 001), which was higher in breast- compared to bottle feeders.
Conclusions
While this data does not specifically answer questions about the direction of the immune response, it does suggest that breastfeeding mothers are immunologically and endocrinologically different. Breastfeeding mothers may be in an immunologically alert state, with both TH-1 and TH-2 arms of the system responsive to antigenic threats.
Implications
This data was collected as pilot data for a recently funded R0-1. Data on 200 mothers are currently being collected with a full range of immune, health, endocrine, and stress measures being explored. Results from the pilot data suggest that lactators and non-lactators are very different and that lactators have a down-regulated stress response and up-regulated immune response compared to non-lactating mothers. These differences may provide a biobehavioral and health benefit to mothers who are lactating.
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