IN PRAISE OF BACTERIA

Just as a brief follow-up to my last post on metabolism boosters, I thought it worth mentioning some research in support of another high-profile food supplement – probiotics.

You’re probably familiar with the marketing claims of yoghurt drinks such as Yakult, Activia etc., promising to maintain a healthy gut through a daily dose of ‘good’ bacteria.  Less well known is that a lot of the research behind these claims was conducted in nice little petri dishes in labs.

Beyond the 'they break down stuff we can't' theory of symbiosis, scientists actually have very little idea of how supplementing our bodies with these miraculous microorganisms can actually benefit our intestines.    

But things are looking up.  A team of researchers at Emory University, Atlanta have just published results unravelling an example of how probiotic bacteria may act biochemically in the body. And it’s quite a surprising one.

The gut is the Piccadilly Circus of the body’s bacterial community.  Lactobacillus rhamnosus is one such inhabitant and has its population regularly bolstered by our consumption of yoghurt and other dairy products.

Using mouse models, the researchers discovered that L. rhamnosus stimulates production of reactive oxygen species (ROS) (part of a group of chemicals called free radicals), by epithelial cells lining the intestine.  These cells have the unenviable task of providing a rigorous internal barrier to foreign pathogens (equivalent to the skin) while also allowing food and other nutrients to be absorbed into the body. 

The ROS trigger a cascade of internal signals within the intestinal cells, promoting the physical migration of these cells to the site of the bowel wound – effectively healing damaged tissue by closing up the gaps in the intestinal wall. 

Importantly though, if you don’t already suffer with a intestinal disorder such as IBS, this would suggest that probiotics probably aren’t making much difference to your overall health.  

And as any beauty product or health food devotee will confirm, we have been indoctrinated to believe antioxidants = good, free radicals = bad.  Skin aging, cancer and all manner of nasties will ensue if we let free radicals run loose in our bodies.  ROS are produced by immune cells as part of the body’s inflammatory response to bacterial infections and an imbalance of these species can contribute to some of the biggest killers of the western world. 

So in a counterintuitive twist, this new research appears to show that ROS do have a beneficial role to play in maintaining gut health.  And slightly worryingly for those of us stocking up on the acai berries and green tea, excessive consumption of the antioxidants which mop up ROS could actually damage our intestines.

Balance, as ever, seems to be the key. 

(An obvious caveat is that L. rhamnosus is just one strain of probiotic bacteria – there are numerous others and they may very well exhibit very different mechanisms of action.

By the way, the photo above is not actually of L. rhamnosus.  I couldn’t find a free one on the web so swiped a photo of R. sphaeroides from some previous research of mine. They look quite similar and I think do the job of illustrating bacteria pretty well.)

Swanson P et al. Enteric commensal bacteria potentiate epithelial restitution via reactive oxygen species-mediated inactivation of focal adhesion kinase phosphatises. PNAS May 9, 2011