More than a million children around the world die from malnutrition each year, but the condition does not result from diet alone — the make-up of microbes in the gut also has a role.

A team led by Jeffrey Gordon at Washington University in St. Louis, Missouri, studied 317 pairs of twins in Malawi. Of these, the authors identified pairs in which one twin had developed a form of severe acute malnutrition called kwashiorkor (pictured). The microbial profiles of these malnourished twins differed from those of their healthy siblings. When both children received therapeutic diets, the malnourished twins' microbiota began to resemble that of their healthy siblings, but it reverted when the children returned to traditional Malawian foods.

The findings could explain the apparent benefit of using antibiotics to treat kwashiorkor, a regime investigated by Mark Manary, also at Washington University in St. Louis, and his group. They conducted a trial with 2,767 Malawian children — including those in Gordon and co-workers' study — in which all children received therapeutic diets and some were treated with antibiotics. Of those given the antibiotic cefdinir, 4.1% died, compared with 7.4% of the children who received a placebo.

Credit: STEPHEN MORRISON/EPA/CORBIS

Science 339, 548–554 (2013) ; New Engl. J. Med. 368, 425–435 (2013)