Yet Another Reason Why Raw Food is Better

How Gut Bacteria Evolved To Feast on Sushi: (You can listen to the audio on the link below the post)

How Gut Bacteria Evolved To Feast On Sushi

About 40,000 years ago, bacteria in the stomachs of Japanese people evolved to digest nori, the seaweed that's used to wrap maki rolls. But the average person from North America doesn't carry this version of the microbe.

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April 7, 2010

Some people will do a lot for sushi.

But at least one bacterium appears to have actually altered its genetic code in order to feast on an ancient version of the maki roll, scientists report in the journal Nature.

The bacterium, Bacteroides plebeius, lives in the human gut, along with trillions of other microbes. And like many gut bacteria it has acquired genetic sequences that allow it to produce lots of different digestive enzymes.

But B. plebeius apparently did not have an enzyme capable of digesting seaweed 40,000 years ago, when people first began to arrive in the Japanese archipelago, says Jan-Hendrik Hehemann, the paper's lead author and a researcher at the University of Victoria in British Columbia, Canada.

There was no need, because it appears "their continental ancestors ate only higher plants," Hehemann says.

On the islands, though, seaweed became a part of the diet. "And the bacteria in the gut had an incentive to access carbohydrate substrates that were present in the seaweed," says Justin Sonnenburg, assistant professor of microbiology and immunology at Stanford University School of Medicine.

How B. plebeius solved that problem might still be a mystery had Hehemann and a team of scientists not been studying a bacterium that lives in the ocean and is often found on a type of red seaweed.

It's the seaweed called nori that's used to wrap some sushi, including maki rolls.

When Hehemann tested some of the genes from this bacterium, he found that, as expected, they made special enzymes to break down nori.

And once the team knew what genes to look for, Hehemann says, it started to poke around in genetic databases to see how many other bacteria carried the same genes.

Not surprisingly, nearly all the bacteria the researchers found live in the ocean, Hehemann says.

The exception was a strain of B. plebeius found in the guts of people in Japan.

The team immediately realized what must have happened, Hehemann says.

When people in Japan began eating seaweed with their rice and fish, they also ingested some bacteria from the ocean. And as these ocean bacteria passed through the intestine, they exchanged bits of genetic code with the gut bacteria.

Bacteria actually do this sort of gene transfer all the time. It provides them with a sort of evolutionary overdrive, Hehemann says.

"This can happen really quickly," he says. So a bacterium that can't digest nori one day, can the next.

This sort of digestive evolution has probably helped humans adapt to lots of new environments and lots of new foods.

Unsurprisingly, bacteria in North American guts don't have the genes to break down seaweed, which means the body can't get calories — energy — from it. And these bacteria probably never will, even if sushi becomes a staple in North America, Hehemann says.

That's because these days, seaweed is roasted before it's used to wrap a maki roll, so the bacteria are dead long before they reach your gut.

And so are the bacteria in most foods in industrialized countries, Sonnenburg says.

"We're undergoing a tremendous experiment right now," he says. "We're consuming a lot of really highly processed calorie-dense food that's incredibly sterile, so they lack the microbial reservoirs for these gene transfer events."

Sonnenburg says that could be a problem for humans because gut bacteria help us digest new foods, modulate our immune systems, and even ward off some diseases.

Related NPR Stories

The Gut Response To What We Eat Nov. 12, 2009

Did Cooking Give Humans An Evolutionary Edge? Aug. 28, 2009

Gut Bacteria May Cause And Fight Disease, Obesity Nov. 4, 2008

Stomach Bacteria Could Prevent Asthma July 18, 2008

I am not meaning to say people need to eat raw meat – I don’t eat any raw meat. (And the article doesn’t even refer to the raw meat itself, but to the type of Algae the sushi is wrapped in – how nowadays it is so overprocessed there is no necessary bacteria in it). There is a point in the article where they discuss how the extreme overprocessing of foods has created these extremely sterile foods that do not allow our body’s bacteria to adapt and develop enzymes for proper digestion, get the most nutrition, and strengthen and develop immunity… The scientists discuss how we are running a gamble experiment with our current nutrition… (It’s very evident in the audio portion, near the end of it.)

I personally think the Raw Food…“diet” (for lack of a better word) is a good idea. We see everyday and increasingly on TV and in the news how the over-processing of food is leading to all kinds of health issues (not all diabetes related). I recently heard somewhere that the reason the French and Italians are so healthy (as a general rule) is because they eat fresh daily. They don’t have all the preservatives that we have in America. I personally notice that I feel better overall and my blood sugars are in MUCH better control when I only consume raw foods as my meal. I’d never thought about Sushi though. It was an interesting read. Thank you Lizmari!!!

Yeah, they were talking about the roasting or cooking/processing of the Algae in the sushi (which is a plant)… not about the raw fish itself. :slight_smile: But yeah, I feel the same as you… It was just a neat read.

I always assumed that the algae part just air dried. I never thought about cooking/processing it.

Yeah, that’s what I thought, too… And maybe back in the day they did, but according to the article, they don’t… it’s all roasted, and cooked extensively… (All the kind we get here in the West, anyway.)

I usually expect better from NPR. Gut bacteria are cultivated. Transplant some americans over to Japan, feed them sushi and nori and amazingly, they grow these gut bacteria. If you have ever been a vegetarian and switched to a meat diet, you know full well that your gut bacteria cannot handle the diet change. give it a few weeks and amazingly you can eat meat all day. And while cooking is certainly useful to kill harmful bacteria and parasites, it is more likely that humans evolved cooking because it makes food more bioavailable and nutritous. Read the book “Catching Fire: How Cooking Made Us Human” for that perspective. It turns out it is a myth that cooking destroys food, properly done cooking actually can dramatically increase the nutritional value of food. It also makes a huge difference in how well you can eat and digest food. Chewing food properly makes a huge difference. If you have ever tried to eat raw meat, and I’m talking a hunk of steak, you will soon understand clearly why cooking evolved.

ps. I eat sushi all the time and I digest it fine.
pps. And nori is roasted.
ppps. I like to watch Gary Taubes discuss diet with Dean Ornish (!v=OdBDQdOKbJQ&feature=related).

I’m starting to understand now (thanks to you guys) why my mother always said “chew your food 40 times before swallowing”. I always thought she was daft, but apparently, she knew more than she was letting on.