Humans have about 100 trillion microbes in their intestines, and scientists are constantly finding that these gut microbes can play a huge role in our lives, potentially contributing to health conditions as far-ranging as obesity and autism. Fecal transplants are taking off as sick people use infusions of healthy gut microbes to treat all kinds of intestinal maladies.

A study published today in Science Translational Medicine finds that some nasty gut microbes may play be partially to blame for a terrible form of malnutrition called kwashiorkor. Researchers took fecal samples from two pairs of human twins in Malawi, Africa, and transplanted the samples into mice. Both pairs included one twin who was healthy, and one twin who had kwashiorkor. The study builds on previous work by the same lab, which identified gut bacteria as a potential contributor to kwashiorkor.

Kwashiorkor occurs when children don’t get enough protein. It can be corrected with the introduction of a better diet, but children who suffer from kwashiorkor in childhood are at risk of having physical or mental problems for the rest of their life if they don’t get help quickly.

In this study, the researchers generally found that the twins who had kwashiorkor tended to have larger amounts of gut microbes that were disease-causing, like E. coli, while the healthy twins had healthier gut microbes. When the mice were given gut microbes from a twin with kwashiorkor, and were also fed a diet mimicking malnutrition in Malawi, the mice tended to suffer severe weight loss and “poor health” compared to mice who got gut bacteria from the healthier twin. The mice who ate standard mouse food lost much less weight and were healthier regardless of which type of gut microbes they received.

This is still very basic research–the paper doesn’t suggest a direct therapy or cure, and, with such a small sample size it is not clear how applicable these results are to other populations where malnutrition is a problem. Another study done by the same lab in Bangladesh found that many children with malnutrition lacked healthy gut biota.

The authors of the new paper suggest that continuing to study the gut microbes in malnourished children could help scientists and doctors assess whether treatments are working, and identify kids who are at a higher risk for severe malnutrition conditions in the future.