Microbial Medicine

Today Jonathan Eisen makes some good points about probiotics being sold like snake oil miracle cures.

I’ll agree that it’s a growing problem. I often find people on message boards advocating probiotic treatments, despite the lack of evidence-based support for such actions. I always tell them the same thing: Popping some Lactobacillus acidophilus isn’t likely to hurt, but there’s little proof that it will help you, either.

Lactobacillus acidophilus
Lactobacillus acidophilus

Someone was even asking about fecal transplant bacteriotherapy the other day, after reading Carl Zimmer’s excellent article about how it can treat severe Clostridium difficile.

Look, I totally understand why people grasp at straws and search for anything that might help. Living with a chronic condition that has no cure sucks. Wasting your money on treatments that don’t help, though, will only make you lighter in the wallet and still sick. The problem with probiotics in this case are two-fold:

The first problem is that we just don’t understand the composition of the gut well enough to start trying to theraputically change the composition of your microflora. It’s an enormously complex ecosystem, and we’re just now dipping our toes into the water with initiatives like the Human Microbiome Project. Scientists are studying this with a great deal of interest though. In fact, he other day I stumbled across a study showing that by treating rats with antibiotics, then doing fecal transplant, a team could create long-term alterations in the microbiota of rats. This is pretty exciting stuff, but it’s only the first of many advances that will be needed to prove the feasibility of bacteriotherapy. The next steps will be to figure out which microbes we want in our guts, which we don’t, and how we can create a stable environment for those beneficial species. This will undoubtedly take a while.

The other problem with using probiotics to treat gut conditions is that most of these disorders (IBS/IBD/Crohn’s) have both genetic and environmental factors that contribute to the aetiology. I’m most familiar with Crohn’s Disease, which occurs when cells in the intestinal walls aren’t able to keep microbes out properly, so the immune system kicks into overdrive. So far, it hasn’t been linked to any specific species, which seems to make it a poor target for microbial therapy. Add in the fact that there are often systemic inflammatory problems like arthritis and back problems, and it’s not at all clear that we can treat this by just swapping around the microbes in the gut.

So to sum things up, using probiotics to seriously treat disease will have to wait until we better understand both the diseases in question and host/microbe interactions. That said, research into the microbiome is enormously promising, and I do believe that microbial medicine will someday be commonplace. It’s just that we still have a long way to go.

image source

Bacteria and Bad Breath

Over at Ask Metafilter, Srudolph asks:My son and his dad (my former husband) never have bad breath. How is this possible?

Halitosis is mostly caused by microorganisms breaking down the food particles left in our mouths. Right, now, we know that people can have fairly different microbial populations, but don’t have a good handle on why that is. Some of it is certainly environmental, related to eating habits and such, but some of it also depends on personal factors. The immune system plays a role in culling these bacteria, and there are probably other contributors, like slight differences in the pH of your saliva, that might make all the difference.

Factors like these last two may be partially genetic, which explains why your husband and son have similarly fresh breath. Since we don’t yet know enough about these dynamic microbial ecosystems to control them, your best bet is to brush after meals, and be glad that you don’t have to kiss a smelly spouse.

If you’re interested in learning more about the trillions of microorganisms that inhabit your body, read up on the Human Microbiome Project, which is trying to characterize and understand them.