Secretory immunoglobulin A (sIgA) is an antibody that tolerates harsh intestinal environments and provides effective protection against pathogens that may penetrate the mucosal lining on the human digestive system. Infants have immature immune systems and are unable to produce adequate amounts of sIgA until childhood and therefore susceptible to infections. sIgA in maternal milk provides effective protection for breastfed infants against local pathogens, against which the mother has immunological memory. Animal studies have shown that vitamin A (VA) deficiency suppresses sIgA levels in the animal’s saliva and intestines, but it is unknown if VA also impacts sIgA levels in milk. The objective of this study was to evaluate if maternal general nutrition, VA status, and milk retinol levels correlate with breast milk sIgA levels.
We used cross-sectional data from 59 exclusively breastfeeding, rural Kenyan mothers without signs of acute infection or inflammation and their milk. Regression models were applied, using the outcome milk sIgA. The predictors included indicators of maternal nutrition and milk retinol.
Maternal Arm Fat Area (p=.022) and milk retinol (p=.032) positively predicted sIgA.
Milk VA supplies infants with the vitamin necessary to develop the immune system and fight against infections long-term. While this role of milk VA is undeniable, our findings suggest that there may be an additional, previously unrecognized pathway linking lower morbidity and mortality among infants consuming milk rich in VA. This pathway may involve sIgA as a key substance providing immediate protection for the infants against pathogens.