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Tuesday, May 24, 2011

Humans have three enterotypes

Thanks to the efforts of 85 researchers from more than ten countries, we have a better understanding of the ecosystem that is the human gut. It seems that people from the Americas, Europe and Japan all have one of three gut environments, or enterotypes.

Each enterotype, like any ecosystem, is the sum of all the types of flora and fauna within that system. In this case, that flora and fauna are all microscopic. You may be wondering how the researchers determined what kinds of flora were in each person’s intestinal tract. After all, many of these microbes have never been observed, let alone grown in a lab. I’ll let the words ‘sequenced faecal metagenomes’ sink in for a minute. Yes, they sequenced DNA from stool samples.

When they compared results from 22 people living in four different countries, they found that the country of origin did not matter. As with A, B, O blood types, the three enterotypes were found at each location and did not seem to discriminate between sex, weight or age. It’s not clear why this should be. It could be that each individual is randomly colonized by a package of flora soon after birth.

There are a few caveats. For one thing, none of the tested volunteers were from non-industrial cities where the diet and lifestyle, and thus the gut flora, might be completely different. Also, 22 is a very small sample size, even when combined with an additional 17 people form earlier studies.

Nonetheless, if this result is valid, it could have widespread implications for how we eat and how we treat illnesses. For example, enterotype 1 produces more vitamin B7 (biotin) and enterotype 2 more vitamin B1 (thiamine). Knowing your enterotype might one day allow for individualized diets. In addition, rather than prescribing antibiotics that kill all your intestinal microbes, doctors might give you a cocktail containing your own enterotype mix in an effort to outcompete the bad bacteria.

Hat tip: The Skeptics' Guide to the Universe.