Children who grow up malnourished lag behind healthy kids in terms of their height and weight. But a new study finds that they also fall behind in the bacteria in their guts. The findings may explain why weight gains are often temporary, and malnourished children remain underweight compared to healthy children in the long-term.
Babies get their first gut bacteria from their mothers during birth. As they eat new foods, the community that live in the intestines changes and matures throughout the first few years of life. By age three, an "adult" community has taken up residence in the gut, and helps the body to break down food and boost the immune system. But in malnourished children, scarce or low-quality food and infections from poor sanitation result in an underdeveloped bacterial community that looks more like the inhabitants of a young child.
A study by Sathish Subramanian and colleagues published yesterday in Nature finds that children living in a slum in Dhaka, Bangladesh who were treated for malnutrition with nutrient-dense foods, have a temporary improvement in their gut bacteria. But the community will regress back to a younger state months after the therapy stops. The results correlate with observations that nutritional therapy saves lives, but cannot correct problems such as stunted growth, learning disabilities and a weakened immune system.
Initially, the researchers took stool samples from healthy children of a range of ages from the same slum. By looking at the identity of the bacteria from their intestines, the researchers could figure out what types of bacteria live in the gut at different times. They then looked at the bacterial communities from children receiving therapeutic foods to treat malnutrition to determine the "age" of their communities throughout the course of their treatment.
In a commentary on the study, Elizabeth Costello, PhD, and David Relman, MD, researchers in the Department of Microbiology and Immunology at Stanford, compare the gut communities of malnourished children to a degraded environment, such as a clear-cut rainforest that becomes choked with weeds. Just as it is difficult to clear the weeds and restore the original rainforest trees, it is challenging to rehabilitate the gut communities of chronically malnourished children.
"Degraded communities can be resistant or resilient to change, and although host health can be restored, youth cannot," write Costello and Relman. "Thus, an ounce of prevention is likely to be worth a pound of cure and, as with other types of developmental delays, early intervention may be crucial."
The study's authors suggest that monitoring the gut communities of impoverished children may be one way to kept tabs on their health, and to measure if experimental nutritional treatments are working. Just like height or weight, the age of the gut bacterial community may be one way to track a child's growth and development.
Patricia Waldron is a science writing intern in the medical school’s Office of Communication & Public Affairs.