Why Can’t Once-Malnourished Children “Catch Up”? Answer May Lie in Gut

Malnourished children have immature gut bug systems, scientists find.

A photo of children suffering from maladies associated with malnutrition in Bangladesh.

Children suffering from maladies associated with malnutrition in Bangladesh, where the author of a new study researched children's digestive tracts

PHOTOGRAPH BY RON HAVIV, VII

Karen Weintraub

for National Geographic

Published June 4, 2014

Doctors have learned how to stop malnutrition from killing small children, but they've been unable to figure out why these children remain at a disadvantage even after they're well fed. A new study suggests the answer may lie in gut bugs.

Infants and toddlers who are malnourished have an immature ecosystem of microbial organisms in their digestive tracts, according to new research published in this week's Nature. The current treatment for malnourishment doesn't help the child's system catch up to normal maturity, which may explain why formerly malnourished children still suffer from short height, immune problems, and intellectual delays, said Jeffrey I. Gordon, who studies the gut microbiome at Washington University in St. Louis and who led the research.

"There's something lacking in our current approach to treatment," said Gordon, who suspects the children may need to eat therapeutic foods for longer and/or get supplements of probiotics, or beneficial microorganisms, to catch up. "We need to think of food as interacting with this microbial organ." (See our Future of Food series.)

The study also outlined a method for determining the maturity of a child's gut bugs, which could be used in other health-related contexts.

Gordon said he is currently comparing the ecosystems from the healthy Bangladeshi children cited in this study with the gut bug populations of healthy infants and toddlers in Malawi, South Africa, India, Peru, and the United States. Early indications suggest there are common patterns of development around the world, he said.

A child's gut bugs, immune system, and brain appear to develop simultaneously, Gordon said. Once researchers know what normal, healthy gut bug populations are supposed to look like as a child develops, they can better understand—and treat—what goes wrong in conditions like malnutrition, and maybe even autism, he said.

"We as humans, when we're developing after birth, there's a microbial dimension to this development that we should monitor, and measure," Gordon said. "Perhaps healthy growth and attainment of our full potential requires healthy development of our [gut] microbial organ, and also microbes living in other parts of our bodies." (Related: "What Lives in Your Gut?")

Babies are born without any microbes in their digestive tract. The microbes that colonize the body over the next two years likely affect the child's health throughout its life.

"The microbes we acquire early in life are very important," said Martin Blaser, a professor of medicine and microbiology at the NYU Langone Medical Center and author of a book about this early development called Missing Microbes. "We really have to understand the dynamics of how the microbiome develops in young children."

Blaser praised the new paper for its insights into malnutrition and benchmarks for normal development.

"This provides more evidence that the early life microbiota is vulnerable," he said.

To conduct the new study, Gordon and his team collected monthly fecal samples from 50 healthy Bangladeshi children for the first two years of their lives. From those children, they found that a combination of 24 species could be used to predict the maturity of a child's microbial ecosystem.

When these healthy children had diarrhea, their microbial systems regressed but quickly bounced back, the research showed.

The researchers then examined fecal samples from 64 infants and toddlers hospitalized for malnutrition and diarrhea. The children received antibiotics and therapeutic foods for a week or two and then their families were taught how to better support their nutrition.

But these children, who had an immature balance of microbes to begin with, only got a little maturity bounce at the beginning, then remained far behind their peers, Gordon said.

"Food alone wasn't able to repair the maturity," he said.