Young children recovering from severe malnutrition could benefit from eating chickpea and peanut flour and bananas, among other supplemental foods, that rebuild healthy bacteria in their digestive tracts, according to a new study of Bangladeshi children.
Malnutrition disrupts normal gut bacterial communities in ways that make it difficult for children to gain weight and experience normal metabolism and bone growth, researchers say, making it important to know which bacteria are needed and how to replenish them in children.
"One question arising from these observations is, how do we design optimal foods that steer a microbiota into an age-appropriate and healthy state?" said Jeanette Gehrig of Washington University School of Medicine, St. Louis and her colleagues in the study published July 12 in Science.
Gehrig and her colleagues in the lab of Jeffrey Gordon, director of Washington University at St. Louis' Edison Family Center for Genome Sciences and Systems Biology, designed a multi-step study to answer this question, beginning with an in-depth look at how gut bacteria and essential growth and development proteins differ in children with severe malnutrition, those recovering from malnutrition and those with a healthy gut.
The scientists tracked bacteria and proteins in blood for a year among 343 Bangladeshi children ages six to 36 months who were being treated for severe acute malnutrition, the most extreme malnutrition level measured by the World Health Organization. Children in this group have very low body weight for height and significant muscle wasting and may suffer from a condition called nutritional edema which causes swelling of the face and limbs.
Their results revealed that malnourished children have a gut microbial community that looks like the community in younger, healthier children. "This microbiota 'immaturity' was more pronounced in children with severe acute malnutrition as compared to those with moderate acute malnutrition" who had been treated with common supplemental foods such as lentil-rice mixes, said Gehrig and colleagues.
By comparing the bacterial data with protein data in the children, other members of Gordon's team used a machine learning algorithm to determine a minimal set of gut bacteria associated with healthy, age-appropriate growth and development.
The researchers then transplanted the bacterial community from a child with moderate acute malnutrition into the guts of mice engineered to have no other bacteria in their digestive tract. The goal, said Gordon, was to discover what kinds of supplemental foods could repair this immature gut bacterial community and bring it up to a mature state.
In tests with mice and pigs with similarly "clean" guts, Gordon and colleagues found that protein-rich diets containing chickpea and peanut flours, bananas and tilapia were associated with the most strains of healthy, mature bacteria.
One "sobering observation," the researchers noted, was that foods typically eaten by 18-month-old children in the region — including rice, milk powder, potato, spinach and sweet pumpkin — were less likely to be associated with the sought-after mature bacterial strains.
"Rice gruel with milk is the most common first complementary food given to Bangladeshi children," Gehrig and colleagues write.
In the final part of the study, the researchers tested how three different supplemental food mixes affected the gut bacteria and growth and development protein levels in 63 children who had moderate acute malnutrition. In this smaller group, a supplemental food mix containing chickpea and peanut flours and raw banana was the best at raising the level of proteins found in healthy children and lowering the abundance of certain proteins, such as those associated with muscle wasting, that are found at elevated levels in children with severe acute malnutrition.
This mix was also the most effective at "reconfiguring the gut bacterial community to a mature state similar to that characteristic of healthy Bangladeshi children," Gehrig and colleagues said.
The researchers hope that this protein-rich supplement can be tested in larger groups of malnourished children living around the world, to learn more about how repairing immature gut bacteria might affect their future growth and health.