Wednesday, December 2, 2009

Getting Down and Dirty

OK, so I didn't blog for a couple of weeks, but this one is worth sharing...

Finally, some solid evidence to support the hygiene hypothesis. You've heard this one before, we need to eat dirt when we're small if we're going to be healthy.

It's an idea that has a solid biological underpinning. When we're small, our immune system is yet to properly develop. Exposure to all the 'normal' stuff in our lives (dirt, microbes and the like), trains our immune system to recognize the good from the bad. The problem, according to the hygiene hypothesis, is that if we aren't exposed to all the normal stuff when we're small, our bodies never learn the difference and so over react when we come in contact with those same materials later. That over reaction is the allergy response. The hygiene hypothesis suggests we should expose ourselves to far more dirt as youngsters if we want to be healthy in the long run. The problem with the hypothesis is that it's relied on epidemiological data for its proof. And, as any scientist can tell you, correlation (which is what you find with epidemiology) is not causation.

A couple of new studies are providing that causation. In a European study a group of researchers found that pigs housed outdoors for the first part of life had higher levels of lactobacilli and less immune activity in their guts than pigs kept in an isolation room. What does that mean? Lactobacilli are known to help prevent E. coli and Salmonella from colonizing the gut, which is good news if you want to avoid food poisoning. And as far as the immune activity, again, if the problem we're worried about is hyperactive immune systems, this is a good thing.

The second study is out of the University of California. Here a group of researchers looked at the bacteria naturally found on the skin. They discovered that Staphylococci sp. produce a compound that blocks a key step in the inflammation process. Which means that when you get a cut or scrape, it's the bacteria on your skin that are preventing your immune system from overreacting. That's a good thing: too much immune response and you'll get puffiness, rashes, heat and extra pain.

What all this is telling us is that we have this highly evolved, and tightly intertwined relationship with the bacteria that inhabit our body. These organisms block 'bad' bacteria from colonizing, and it's when they're not there that our immune system gets out of whack, leading to increased levels of immune response, aka allergies.

The irony is that on one level we appreciate that, as we see ads for yogurt containing high levels of lactobacilli. And at the same time, we live in a world that's selling buckets full of hand sanitizers, which are removing the very bacteria we need to protect ourselves.

What should we do? Follow our mother's advice, wash our hands, don't stick your fingers in your eyes, don't chew on your pen, and respect the fact we live in a bacterial world.

If we respect that, we'll only do ourselves good!

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