By Pat Bailey
A UC Davis-led study of nursing mothers in The Gambia shows how environment changes breast milk content
In a newly published study, UC Davis researchers and their colleagues, paint the picture of an elegant web of cause-and-effect that connects climate, the breast milk of nursing moms, gut microbes and the health of breast fed infants.
The research is part of a long-running. cross-disciplinary project at UC Davis studying milk and its role in nutrition. For example, last year UC Davis scientists and colleagues at Washington University St. Louis worked with both children and animal models to show how milk compounds could alter gut microbe composition and affect health. UC Davis researchers also led a consortium to study the “milk genome,” the collection of all genes related to producing milk.
Mothers and babies in The Gambia
The new study, appearing online in the journal Scientific Reports, involved 33 women and their babies in the West African nation of The Gambia. It found that complex breast milk sugars called oligosaccharides helped protect nursing babies from illness and also influenced the mixture of microbes in the infants’ guts.
The researchers also demonstrated that seasonal changes in food availability could affect breast milk composition and the protective quality of the gut microbiota. And those changes, in turn, impacted the health and growth of the breastfed infants.
“Our findings provide evidence that specific human milk oligosaccharides can alter the composition of breast milk, making it more protective against infection and allowing the infant to invest energy in growth rather than fending off disease,” said corresponding author Angela Zivkovic, an assistant professor of nutrition at UC Davis.
Composition of breast-milk sugars and infant health
Human milk oligosaccharides occur abundantly as more than 200 different chemical structures. It’s been known for some time that these complex sugars play an important role in infant health by supporting the growth of beneficial bacteria in the baby’s gut. And these gut bacteria have been shown to play a key role in fending off infectious illnesses.
Little is known, however, about how changes in the composition of the breast milk sugars might affect the health and growth of infants, especially those living in areas where infection rates are high.
In this new study, researchers monitored the composition of the oligosaccharides in the mothers’ milk and examined the infants’ gut microbiota at 4 weeks, 16 weeks and 20 weeks after the babies were born. Then they analyzed the data for possible relationships to the health and growth of the babies and the status of their gut microbes.
They found that two of the oligosaccharides, lacto-N-fucopentaose and 3′-sialyllactose, had a direct relationship to the infants’ health and growth. High levels of the former were associated with a decrease in illness and improved growth, measured as height for age, and the latter proved to be a good indicator of infant growth, as measured by weight per age.
Influence of wet and dry seasons
The researchers also were interested in how seasonal shifts in food availability, which significantly impact the mothers’ diets, might be reflected in breast milk composition and infant health.
The Gambia has two distinct seasons, the wet season from July to October and the dry season from November to June.
The wet season is also known as the “hungry” season because it is the time of year when food supplies tend to be depleted, infection rates rise and the farming workload is highest. In contrast, the dry, or “harvest,” season is characterized by plentiful food supplies as well as significantly higher energy stores and less illness among the local people.
The researchers found that mothers nursing during the wet or “hungry” season produced significantly less oligosaccharide in their milk than did those nursing during the dry season.
In examining the seasonal makeup of the babies’ gut microbiota, the researchers found that most of the bacteria belonged to the Bifidobacteria genus. In analyzing data from the babies’ gut microbiota, the researchers higher levels of Dialister and Prevotella bacteria were accompanied by lower levels of infection.
In addition, higher levels of Bacteroides bacteria were present in the infants’ guts that had abnormal “calprotectin” – a biomarker associated with intestinal infections.
“We are very interested in which specific dietary factors influence the oligosaccharide composition of mother’s milk,” Zivkovic said. “If we can find the mechanisms that change the composition of breast milk sugars, we may have a new approach for modifying the infant microbiota and ultimately influencing the health and vigor of the nursing baby.”
Collaborators and funding
Working on the study with Zivkovic were UC Davis researchers Jasmine C.C. Davis, who recently completed her graduate studies; Carlito B. Lebrilla, distinguished professor of chemistry; Zachery T. Lewis, who recently completed his postdoctoral studies; David A. Mills, professor in the Department of Food Science and Technology; and Shridevi Krishnan, a researcher in the USDA Western Human Nutrition Research Center. Also collaborating on the study were Robin M. Bernstein of the University of Colorado, Boulder, and Sophie E. Moore and Andrew M. Prentice, both of the Medical Research Council in the U.K.
Funding for the study was provided by the National Institutes of Health, UK Medical Research Council, Bill and Melinda Gates Foundation, Alfred P. Sloan Foundation, and Peter J. Shields Endowed Chair in Dairy Food Science at UC Davis.
Pat Bailey writes about nutrition, agricultural and veterinary sciences for UC Davis Strategic Communications. Follow her on Twitter @UCDavis_Bailey.