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The World Inside

As part of an effort to understand how microbes affect human health, the Guardian's Andrew Anthony sent off a fecal microbiome sample to be analyzed by Paul O'Toole at the BioSciences Institute in Cork, Ireland.

Anthony writes that his microbiome appears fairly healthy — mostly firmicutes and bacteroidetes on the phylum level, but also including roseburia, which produce butyrate, and lachnospira, but fewer bacteroides and alistipes than usual.

There were, though, a few inhabitants that O'Toole struggled to make sense of. For instance, Anthony's sample included high levels of natranaerobius, a microbe that thrives in salty and alkaline conditions — though Anthony tells O'Toole that he didn't eat much sushi. Still, O'Toole was able to determine much of Anthony's diet from the microbes he saw, including that Anthony doesn't eat meat but does eat a lot of vegetables and fiber, something Anthony suggested to O'Toole "must be satisfying."

"It's a bit spooky all right," O'Toole tells him. "But it made me think about the utility of it. I mean, it's not particularly useful to tell people what they eat."

Instead, O'Toole is more interested in the links between the microbiome and health, particularly the health of elderly people, as they become less able to turn protein into muscle and as microbes in the gut may affect mental states.

"There are physiological reasons like Alzheimer's and senile dementia that explain rapid cognitive impairment," O'Toole says. "But the rate of loss could also be affected by compounds made by bacteria, and that's what we're targeting. Bacteria produce chemicals, which are analogs — in other words they look identical to normal human transmitters. What we hope is that we can improve the ability of old people to process data."