A fascinating study of young twins in Malawi in sub-Saharan Africa reveals that intestinal bacteria might be responsible for a form of severe childhood malnutrition called kwashiorkor - associated with swollen bellies, liver damage, skin ulcerations, loss of appetite and wasting.
Experts have long wondered why some children in Malawi are malnourished in this way but not others - even those in the same household and who eat the same foods.
Gut microbes play a huge role in our daily lives, extracting nutrients and calories from our diet, synthesizing vitamins and nutrients and even helping to shape our immune systems.
Carried out by Washington University School of Medicine in St. Louis, this study shows how gut microbes and a poor diet may be combining to cause malnutrition. In fact, gut microbes from malnourished children even caused dramatic weight loss and altered metabolism in mice fed a nutrient-poor diet, which didn’t happen with gut microbes from healthy children.
The typical Malawian diet of corn-based porridge doesn’t have enough vitamins and minerals for proper development. Interestingly, gut microbes from malnourished children don’t seem to mature normally the way they do in healthy children.
The standard treatment for malnutrition is a high-calorie, peanut-based, nutrient-rich therapeutic food. However, therapeutic food only has a transient effect. Once treatment is discontinued, intestinal microbes in malnourished children go back to being immature and dysfunctional.
Malnourished children do gain weight when treated with therapeutic food. But they still remain at high risk for stunted growth, neurological problems and even malnutrition and death after treatment is stopped.
This study followed 317 sets of twins during the first three years of their lives. During this time, half of the twin pairs remained healthy - while in the others, either one or both twins developed malnutrition. This occurred just as often in fraternal twins as identical twins, suggesting that factors other than human genes were involved.
The research team tracked gut microbes just before, during and after treatment with therapeutic food. Four weeks after therapeutic food was discontinued, the genes of gut microbes from malnourished children failed to mature or even regressed, while those from healthy co-twins matured normally.
Next, researchers transplanted gut microbes from either healthy or malnourished co-twins into groups of germ-free mice raised under sterile conditions.
They found that mice transplanted with malnourished children's gut microbes that ate a typical Malawian diet experienced weight loss, while those with the healthy twin's gut microbes and the same nutrient-deficient diet did not. And although the genes of malnourished mice matured when they were fed therapeutic food, they tended to revert to a malnourished state when the nutrient-poor village diet was resumed.
Further, the research team also found that mice with gut microbes transplanted from a malnourished twin carried bacteria associated with human illnesses such as inflammatory bowel disease.
Not only that, the combination of a nutrient-deficient diet and malnourished genes completely changed carbohydrate and amino acid metabolism and reduced sulfur availability in mice, which may have helped to cause weight loss.
Clearly, additional studies are needed to completely understand the role gut microbes play in severe malnutrition. One solution may be to trigger genetic development in gut microbes from malnourished kids - and supplementing therapeutic food with beneficial gut bacteria may be part of the solution.