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The sushi-digesting gut

Sushi poster

The goofiness of culturology doesn't always stop at fuzzy fantasies about ethnic-powered cherry blossom appreciation and negative-space discernment and robot chumminess. Sometimes it gets down and physical, as seen in mightily suspicious claims of magical ethnic hearing powers and super-long Japanese intestines.

But wait – hold those bowels! Maybe there is something special going on in Japanese guts! Or so says a researcher in France, who claims to have found evidence of enhanced nori-digesting ability inside those insides. Uh-oh! I've long joked that I'd have a heart attack if any of the common and loopy "uniquely Japanese" claims ever turned out to be true; is this my end in sight?

Well, not quite, but there still seems to be something interesting going on. As reported in perfectly respectable journals including Nature, Mirjam Czjzek, a chemist at the Pierre and Marie Curie University in Paris, found bacteria in the gut of some Japanese that excrete enzymes able to efficiently break down the nori seaweed found in sushi and other dishes. Why would bacteria that live in human intestines have this ability? The researchers suggest that it may have come from marine bacteria that make seaweed part of their normal diet, which were ingested by nori-eating people, and which then genetically transferred their enzyme-producing ability to the normal intestinal bacteria they met. (Bacteria can do crazy things like that.) 

See the link for more details; it's rather interesting. You'll probably see summaries in many other news outlets too. But science news like this doesn't always get reported and re-reported accurately, so take care to note what the researchers aren't claiming. There's no claim of special enzyme production or anything else different in the Japanese gut itself. There's nothing special in the Japanese human DNA itself that's being passed down. It's the bacteria found in the gut, at least in some individuals, that have the unusual genes and the unexpected ability. The basic idea – that eating a given food may introduce you to bacteria that are good at digesting that food – isn't itself the least surprising. The newsworthy part is the possibility that the ingested nori-eating bacteria may have transferred their ability to other gut-dwelling bacteria, and (the big picture item) that similar transfers involving other foods may have shaped all humans' internal flora immensely over our history. 

There are a lot of questions still hanging. Many people have pointed out that the study's sample size of subjects was very small, and thus the results are quite tentative, especially on whether non-Japanese who eat sushi might have the bacteria. Also, I'm left scratching my head over how things work at the individual level; after reading several articles on the findings, I don't yet see whether there's a claim that the transfer of genes from marine bacteria to gut bacteria happens anew within each individual who eats plenty of nori, or whether such modified intestinal bacteria are passed from person to person. (If the latter: How?)

But in any case, it all points to an actual Japanese difference. Of sorts. Not in "the Japanese" themselves, but rather in the hitchhiker bacteria they carry. Or some of them (and, maybe, many non-Japanese too) carry. And it's all quite tentative and need of further study.

Still, what with all the completely unsupported "uniquely Japanese" nonsense out there, this may be at least something worth talking about!


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