All Your Guts Are Belong To Us (What's Your Enterotype?)

Your intestines circa 1900.

A recent study published in Nature and noted in the New York Times has discovered the intestinal ecosystems of human beings fall into distinct types.  While we all host many different varieties of bacteria, our guts are apparently dominated by one particular type, or family, of microbes, while other varieties are less abundant.

For example, what the study calls Enterotype 1 consists primarily of Bacteroides, while Enterotype 2 hosts high levels of bacteria from the genus Prevotella.

Different bacteria “do” different things in the intestines.  For example, the Type 2 bacteria synthesize enzymes that produce vitamin B1 (thiamine).  Type 1 synthesizes enzymes that produce vitamin B7 (biotin).  I would speculate that other vitamins that are synthesized in the gut, such as vitamin K2, are also produced at differing rates by different enterotypes.

The study included 400 individuals from Japan, Europe, and the United States.  Three distinct enterotypes where discovered.  Interestingly, each subject’s enterotype was not associated with age, gender, weight, health, or nationality.

So what determines the makeup of your biotic community?  And why does it matter?

Vitamin Factory

For those people with Type 2 biotic communities, are blood levels of vitamin B1 consistently higher?  What kinds of physiological effects would this have?  One study found thiamine supplementation increased self-reported mood, energy, and alertness, and improved measured reaction times.  A “built-in” supply of thiamine might prevent a wide range of diseases in Enterotype 2 individuals.  They might get fewer cataracts.  They might be less vulnerable to kidney disease.  They might experience fewer deleterious effects from consuming alcohol (alcohol destroys thiamine).  They might be less likely to be effected by Alzheimer’s and other forms dementia.

This is pure speculation on my part — I have no idea if thiamine blood levels are significantly higher in Enterotype 2 individuals (and if they are higher, if they are high enough to have any kind of therapeutic effect).  Still, it’s in intriguing possibility.

Enterotype 1 individuals might experience benefits from higher blood levels of biotin, including better insulin sensitivity (less risk of Type 2 diabetes), strong fingernails, and glossy hair.

Having a biotic community capable of producing abundant amounts of vitamin K2 could have significant positive effects on health, protecting against heart disease, tooth decay, and osteoporosis.

Diet, or Random Colonization?

The researchers speculate that as infants, our guts are colonized more-or-less randomly by one particular group of bacteria.  Those that get an early foothold then stick around for the host’s entire lifetime.  Perhaps we inherit the biotic community of our parents and other caretakers, just as we inherit language and culture.

Lactobacillus -- they even look friendly.

Another possibility is diet.  This study found diet-related differences in biotic composition between African-Americans and native Africans.  African-Amercians in the study consumed more animal products than the native Africans, and were found to have higher levels of 7-α dehydroxylating bacteria (which produce hydrogen) and lower levels of Lactobacillus plantarum (which produce methane, and are generally protective against other disease-causing bacteria in the gut).  The researchers hypothesize that the higher levels of hydrogen-producing bacteria in the gut are responsible for the higher rates of colorectal cancer in African-Americans (as compared to native Africans).

Does this mean that eating meat increases “bad” bacteria, and thus increases the risk of colorectal cancer?  Maybe.  However, the Inuit, after switching from a native diet (very high protein, low carbohydrate, very low fruit/veg) to a standard Western diet (lots of refined flour and sugar, refined vegetable oils) experienced skyrocketing rates of colorectal and other cancers.  So protein isn’t the problem.

So wrong, for so many reasons.

This animal study points to refined vegetable oil as being the culprit.  Animals fed a diet supplemented with corn oil showed increased levels of a number of risk factors for colon cancer (including higher levels of 7-α dehydroxylating bacteria).  High levels of fish oil supplementation had no negative effect.  Once again, high omega-6 fatty acid consumption is shown to have a deleterious effect on health.

In other words, it’s probably not the meat that increases levels of the “bad” bacteria, and thus increases cancer risk.  It’s probably the french fries cooked in refined vegetable oil.  This explains the increased cancer risk for both African-Amercians and Inuits eating the standard American diet.

Still, none of this is evidence that diet is linked to enterotype.  The “luck of the draw”/infant colonization hypothesis is just as likely.  Still, diet does have an effect on our biotic community, regardless of our enterotype.

What To Do?

I looking forward to learning more about enterotypes.  Should we be consuming different types of probiotic (and prebiotic) foods in order to support our own particular gut ecosystem?  Are people of different enterotypes more or less vulnerable to certain diseases?

Until more is learned, I’ll keep doing the following to keep my gut bugs happy:

• don’t eat refined vegetable oils (corn, sunflower, canola, etc.)
• limit omega-6 from other sources (grain-fed meat & dairy, nuts and seeds)
• eat soluble fiber and other prebiotic foods (artichokes, asparagus)
• eat fermented foods with live cultures (homemade sauerkraut)
• limit gluten consumption (bread, pasta) and lectins (beans, nightshade vegetables) — both of which can disrupt the intestinal lining
• don’t take antibiotics unless absolutely necessary

We Are Many

Human beings are giant walking colonies of human cells living symbiotically with bacteria.  Parts of the body once thought to be sterile, like the lungs, are now found to be colonized by microbes, just as our skin, nose, mouths and bowels are.  The makeup of our biotic communities have a profound impact on our immune systems, our ability to digest food, and our ability to synthesize certain vitamins.  Not all “germs” are our enemies — many varieties help us thrive.

It’s a little weird to think of yourself as a territory to be colonized, but that’s the way it is.  It’s a microbial world — we just live in it.