Mastitis Is Associated with Increased Free Fatty Acids, Somatic Cell Count, and Interleukin-8 Concentrations in Human Milk

Background: Research in bovine lactation has demonstrated that milk produced by a mammary gland displaying inflammation-based symptoms of mastitis has increased levels of free fatty acids (FFAs) compared with milk produced by a contralateral asymptomatic gland. However, the effects of mastitis on lipid classes in milk have not been investigated in humans. Methods: The study described here compared milk collected from the symptomatic breast of women with mastitis (n = 14) with that collected from the contralateral asymptomatic breast to determine if mastitis caused alterations in the quantity of total lipids, FFAs, and phospholipids (PLs), as well as the fatty acid profiles of these lipid classes. To assess their efficacy as biomarkers of mastitis, samples were also analyzed for selected markers of local inflammation: sodium, somatic cell count (SCC), and interleukin-8 (IL-8). Results: FFAs were higher in milk from the mastitic breast compared with that from the healthy breast (1.31 vs. 1.07 +/- 0.10 g/100 g of lipid, p < 0.05). Similarly, SCC and IL-8 were elevated roughly 10-fold in milk from mastitic breasts, compared with milk from healthy breasts, and sodium tended to be higher in milk from mastitic breasts (p < 0.10). However, there were no differences in total lipid, PLs, or fatty acid profiles within each lipid class. Conclusions: In summary, mastitis is associated with increased lipolysis in the human breast but not alterations in milk fat synthesis, as evidenced by a lack of alteration in total milk lipids. Additionally, these results indicate that SCC and IL-8 may be better indicators of mammary inflammation than sodium content.