Prebiotics in human breast milk are associated with infant weight

Human breast milk contains nutrients and compounds that are beneficial for infants. Human milk oligosaccharides (HMOs) are a group of important complex carbohydrates that are found in breast milk. These HMOs are important in the developing infant because they serve as a prebiotic, helping to shape the infant’s gut microbiome by facilitating the selection of beneficial bacteria. The link between gut microbiota composition and infant obesity has led to speculation that HMOs might affect certain bacteria that in turn lead to decreased body fat. Because HMO composition of female breast milk varies over the course of lactation, researchers in Oklahoma and California tested to see whether differences in milk HMO content are associated with infant body weight. The results of their study were published in The American Journal of Clinical Nutrition.

Twenty-five mother-infant pairs participated in this study. On average, the mothers were 29.5 years of age and overweight before conception. When the infants were 1 month and 6 months old, the mothers supplied breast milk samples to test for HMO composition. Concurrently, the infants’ body fat composition, weight, and length were measured.

The findings suggest that HMOs are associated with infant body weight, fat mass, and lean mass at both 1 month and 6 months. A diversity of HMOs, such as LNFFPI (lacto-N-fucopentaose I, a sugar), DSLNT (difucosyl-LNT, a sugar), and FDSLNH (fucosyl-disialyl-lacto-N-hexaose, a sugar) accounted for 33% of the fat mass, which was more than other variables such as gender, and mothers’ pregnancy BMI. infant fat mass than did sex, pregnancy BMI.  LNFPI was inversely associated with 1 month old infant weight, while at 6 months it was inversely associated with weight, lean mass, and fat mass. Overall, the presence of a diverse group of HMOs decreased infant body mass.  While this study has its limitations because it does not specifically test the bacterial composition of the gut, it is a first step to identifying an association between HMOs and infant BMI. As obesity remains an epidemic in the United States, perhaps the microbiome is the first place to look towards to prevent the disease. 

Breastfeeding associated with intelligence later in life

Positive association between breastfeeding and intelligence, between three tiers of family income.  Five IQ points is 1/3 of a standard deviation. 

Editor’s note: I would like to tread very lightly on this topic because of the complexity of the relationships between all the factors discussed and the implications a study like this has.  I probably would not have written about it at all, had it not been published in such a prestigious medical journal, and had been as comprehensive as it was.

Breast milk is the ultimate pre- and probiotic.  It is essential in developing infants’ microbiomes by inoculating and enriching their guts in certain bacterial species.  There have been a number of studies showing alterations of the gut microbiomes of infants that are formula fed, and other studies showing that formula feeding results in a higher risk of asthma and allergies later in life.  The complicated relationship between breastfeeding, the microbiome, and phenotypes like autoimmune diseases are not understood at a mechanistic level.  Still though, it appears that formula feeding, rather than breastfeeding, may have long term consequences for the health of a child.

To that end, there had been a few small scale studies that demonstrated a general association between breastfeeding an IQ.  Just last week, a new study, much more comprehensive than any previous one, delved into this topic and found the same result: duration of breastfeeding was positively associated with IQ, educational level, and income.  The results of this study were published in The Lancet.

In 1982 researchers from Brazil began a longitudinal study using a cohort of over 500 newborn infants.  At that time, one of the things the scientists measured was the duration that each infant was breastfed.  Then, in 2012, the researchers followed up with 3000 of those people in the original study and surveyed them for their educational levels and incomes, as well as measured their IQs.  They discovered that each of these three variables was directly related with the length of breastfeeding, with the possibility that over 12 months of breastfeeding actually slightly decreased each.  Even after factoring in confounding variables such as maternal education, family income, and birthweight the relationship between breastfeeding and IQ, education, and income still held.  The researchers acknowledged the link was tenuous, and that there exists a whole host of other important variables that were not measured in 1982.  Nevertheless, the study suggests that breastfeeding improves intelligence upon adulthood.

Breastfeeding, if possible, is clearly preferred to formula feeding, and studies like this show that it may be in everyone’s interest to promote breastfeeding children.  It will be necessary to decipher the connection between breastfeeding, the microbiome, and these observations, but with more studies in the pipeline showing the value in breastfeeding everyone should be aware of its importance.