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The Malnourished Microbiome

The gut microbiome may be a causal factor of kwashiorkor, a form of severe malnutrition, researchers from Washington University in St. Louis report in Science. WashU's Jeffrey Gordon and his colleagues studied the gut microbiomes of 317 Malawian twin pairs until they turned three. They then focused on nine, well-nourished, same-gender twin pairs and 13 same-gender twin pairs in which one twin developed kwashiorkor. The microbiomes of the healthy twins became more diverse, but as Ed Yong at Not Exactly Rocket Science puts it, "the bacteria of kwashiorkor children stagnated."

The discordant twin pairs were fed a ready-to-use therapeutic food, and the researchers found that their gut bacteria began to mature, but then reverted when the children returned to their traditional diet.

The researchers alsotransplanted the gut microbiomes from three discordant twin pairs into gnotobiotic mice. The mice that received the kwashiorkor microbiomes and that were fed a Malawian-style diet lost weight. "The combination of Malawian diet and kwashiorkor microbiome produced marked weight loss in recipient mice, accompanied by perturbations in amino acid, carbohydrate, and intermediary metabolism that were only transiently ameliorated with RUTF," Gordon and his colleagues write, referring to the ready-to-use therapeutic food.

As Yong notes, though, "the microbes aren't the whole story," but he adds that diet also isn't the whole story — they likely work in conjunction to bring about kwashiorkor. One possibility is that, together, they limit the amount of sulfur in the children's diet. Sulfur, Yong writes is common in animal and cereal proteins, but the Malawian diet is low in those types of protein. Further, Biophilia wadsworthia, which is more common in the microbiomes of children with kwashiorkor, may absorb what little sulfur there is. Further, Yong adds that there is evidence that the kwashiorkor microbiome also interferes with the citric acid cycle.