Gutting it Out

A relatively new and exciting area of science deals with the human gut and the bacteria that inhabit it, making up a microbial community called a “microbiome.” These guys are mostly there to help us out with digestion and other basic things, but we have a lot to learn about them and the roles that they play in our health and disease.

A new study by Bailey et al., published in Brain, Behavior and Immunity, takes a look at the role these intestinal bugs play in responding to stress. It is known that stress can turn on our immune system, which in the short term is a good thing and helps us ward off infections and such. However, long-term stress can cause overactivation of our immune system, which can actually make us sick.

It is also known that the bacteria that live in our gut play a role in activating our immune system. They physically move from inside the gut to the edges of the gut and help turn on immune cells that then go around and police our blood stream to look for invading germs.

What is not known is whether stress changes the bacteria in our gut in a way that interferes with their ability to help us activate our immune system – and this was the focus of the study by Bailey. The researchers used mice to see if stress changed the kinds of bacteria living in the gut and if that changed the ability of the mice to turn on their immune system.

Basically, the answer is yes. Mice that were stressed had a different population of bacteria in their gut than those that weren’t stressed. In looking at the bacteria population in the gut, some types of bacteria decreased in number and some increased in number.

What this means is hard to say at this point because we just don't really know what these bugs are supposed to be doing. But we do know that the way we feel affects the population of bacteria in our gut and that this in turn affects how our immune system behaves.

We also know that the types of foods we eat, the amount of exercise we get, and the amount of sleep we get all influence our gut bacteria as well – not to mention overexposure to antibiotics, which can wipe out the good bacteria along with the bad.

The good news from this study is that things tended to move back towards normal a day or so after the stress was over. So even though stress changes the system, the system seems to recover when stress is removed.

All of this points to more connections between our minds and our bodies. Our emotions have an impact on the physical make up of our bodies and the way that our bodies operate. And the way we treat our bodies has an impact on how well we can control our emotions. Struggling with emotional stress for long periods of time can have long-term effects on your physical health and is another reason to seek help when you feel like you have a difficult time controlling your mood.



Brain, Behavior and Immunity (2011) 25:397-407



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