According to a Dutch study, infants who were breastfed during the first four months of their life developed fewer infections than infants who were not breastfed.
The benefit was only seen when infants were breastfed exclusively for four months, not when they were only breastfed some of the time.
They suspect compounds in breast milk, such as immunoglobulin A (igA) pass from mother to infant and help boost the infant's immune system.
Respiratory and gastrointestinal infections are the most common illnesses in infants. Studies have found respiratory illnesses occurring in up to one-third of all infants and GI infections in up to one-quarter of all infants. Upper respiratory infections include colds, ear infections and throat infections; lower respiratory infections include pneumonia and bronchitis.
Exclusive breastfeeding for six months appeared to confer an even stronger benefit, but so few women in the study did this (1.4%) that these results are not statistically significant.
Nearly all women in the study who exclusively breastfed their babies for four months continued to partially breastfeed for the next two months. So there was little information available for women who breastfed exclusively for four months and then stopped breastfeeding altogether.
The researchers are not sure why breastfeeding would lower infections in infants. They suspect compounds in breast milk, such as immunoglobulin A (igA) pass from mother to infant and help boost the infant's immune system. The researchers are also unsure why this effect wasn't seen in intermittently breastfed infants. They suspect that adding formula or solid food to the diet somehow blunts the beneficial effect of compounds in breast milk.
Of course, there is a great deal more passing between mother and infant during breastfeeding than just chemicals.
Though there are many good reasons to breastfeed, sometimes physical and practical reasons make breastfeeding difficult or impossible. Michael Green, a pediatrician who was not associated with the study, advises women who are unable to breastfeed their infant for a long time not to feel bad about it. Plenty of healthy adults were never breastfed when they were children.
This study was part of a larger study following Rotterdam women and their offspring from pregnancy through young adulthood. For the breastfeeding study, women with infants aged 6-12 months were mailed questionnaires about breastfeeding and the occurrence of infectious disease in their children. Nearly 4,200 responses were received.
The study results were published online June 21, 2010 and in the July 2010 print issue of the journal Pediatrics. This article is freely available.
Michael D. Green, MD MPH, is a professor of pediatrics and surgery at the University of Pittsburgh School of Medicine and a pediatrician and infectious disease specialist at Children's Hospital of Pittsburgh and Magee-Womens Hospital.