The Immune Status of a New Mother Varies Depending on Her Feeding Strategy

In one of the first studies of its kind, researchers at UC Santa Barbara have found that the immune status of mothers after childbirth depends on how they feed their baby. According to a study published in the journal Scientific Reports, certain inflammatory proteins – substances released as part of an immune response – peak at different times of the day, correlating with whether mothers are breastfeeding, pumping, or bottle-feeding their babies.

Time-of-day Patterns of Proteins and Feeding Strategies

In fact, much of the research on the effects of breastfeeding focuses on the infant, with many findings demonstrating the benefits of breastfeeding for the immune system and the baby’s development. In the long term, mothers who have breastfed also have a lower risk of developing certain cancers and diabetes.

But what about women in the crucial first months to years after the baby is born? To investigate this, Boddy, lead author and co-principal investigator Carmen Hové and their team followed a group of 96 women in the Seattle area who had given birth within the last six months, collecting their saliva twice over a 24-hour period, once before bed and a second time in the morning upon waking. Because the COVID-19 pandemic had just hit and everyone was in a state of emergency, the researchers found an unexpectedly ideal experimental situation in which the mothers’ environment was strictly controlled for infections that could distort immunity levels.

Breastfeeding has already been shown to elicit a range of inflammatory responses. Inflammation is not always a bad thing – the breast is remodelling, functioning and making things in the body. The diurnal patterns of proteins mean that levels are generally higher in the morning and lower in the evening. The researchers were interested in the unusual levels of these proteins and how they fit with the feeding strategies of the young mothers.

Complexity of Breastfeeding

For several proteins, there were no measurable differences between morning and evening levels, regardless of whether mothers were pumping or breastfeeding. However, for C-reactive protein (CRP), researchers noted that levels peaked in the evening in women who were breastfeeding a lot, reversing the normal diurnal trend. Further research is needed to determine the exact implications of this unique pattern in breastfeeding mothers.

This study highlights the true complexity of breastfeeding after childbirth. Breastfeeding is part of an ongoing physiological negotiation between mother and newborn, one that favors the infant. According to the researchers, there is something in evolutionary biology called the mother-child conflict. The idea is that with two bodies in a maternal unit, the baby will always want a little more than the mother has to give. This research dives into the gray area of postpartum health from a maternal perspective, particularly in the realm of breastfeeding and immunity.

Despite the long-held ideal, propagated by institutes such as the World Health Organization, that “breast is best,” the researchers found that even in their sample of educated, relatively affluent women, there existed a combination of breastfeeding strategies that highlights the challenges of exclusive breastfeeding at the nipple. The researchers hope to explore the topic in more depth and at a more individualized level to identify further patterns for postnatal health and breastfeeding, for example in relation to the various hormones involved in lactation.