Why Are Your Gut Microbes Different From Mine? – The Atlantic

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Medications are also important, from obvious ones like antibiotics and laxatives, to less intuitive ones like antihistamines, antidepressants, and metformin, which is used to treat type 2 diabetes. “It’s one of those elephants in the room,” says Raes. “Everyone knew [that drugs are important] but no one controlled for them.”

Several factors predictably affect the microbiome, including weight, age, gender and consumption of several foods and nutrients, whether it’s bread, fruit, soda, coffee, tea, red wine, or dietary fiber.

Others links were inexplicable. The Dutch team found that the levels of chromogranin A (CgA), a protein secreted by intestinal cells, is strongly linked to the levels of 61 common species of microbe. “We don’t have a good explanation for that, and we know relatively little about this protein,” says Alexandra Zhernakova, who led the study. Meanwhile, Raes found that some Lachnospiraceae bacteria are more common in people who like dark chocolate. (“We don’t understand it, but I think it’s hilarious that you do a Belgian study and one of the factors that comes out is chocolate,” he says.)

And some connections were baffling in their absence. Although many past studies have shown that C-section deliveries and bottle-feeding can change the microbiomes of babies, neither factor affected the communities of the Belgian adults. “That was a shocker,” says Raes. “I think these are effects that wear off over time, but I don’t think that they’re not important.”

Large studies like these are often billed as fishing expeditions, which consider so many correlations that they’re bound to pass off statistical flukes as real results. But Raes argues that his team took extreme care to weed out all but the strongest links. Better still, they cross-checked their results against the Dutch data, and confirmed over 90 percent of their findings. “That blew me away,” he says. This sort of validation is common in genetics, but “is rarely done in the microbiome field,” adds Pat Schloss from the University of Michigan. “It’s something the field needs to start doing as claims that the microbiome controls everything continue to grow.”

But what did the teams miss? What else could explain the differences between our microbiomes, if not the ones they considered?

Why Are Your Gut Microbes Different From Mine? – The Atlantic