An adult’s intestines, when spread out, cover the area of about 1.5 tennis courts, or 7.3 times over my apartment. It is not only a huge, but an important part of your body.
Microbiologists think of the intestine as an external barrier – the same as your skin – because it mediates interactions between you and the “outside” world, for instance the food you eat and the bacteria that come with it. Like your skin, your intestine also acts as a home for symbiotic microbes. Also like the skin, the interactions between the intestine and its resident microbes can lead to either health or disease. This is a huge, booming field of research, with people finding that the gut microbiome, or the collection of all the microbes living in your intestines, may influence everything from your mood to your weight. Today, we are going to zoom in on one particular role of the gut microbiota in your body: making your gut the barrier it’s meant to be.
There has been a lot of discussion in the public and scientific domains about whether “Leaky Gut Syndrome” is a real condition or not. Leaky Gut Syndrome is described as a condition in which stuff that should stay “outside”, i.e. within your intestines, leaks to the “inside”, i.e. into your blood, through your intestine. As you know if you have ever had an infected skin wound, it’s bad news when “outside stuff” like bacteria get into “inside places” below your skin. The same is true in your gut. Problems with the gut barrier have been associated with a whole shebang of different human diseases, from inflammatory bowel disease and celiac disease to worse outcomes for people with type I diabetes or HIV/AIDS.
As you know, correlation does not equal causation, so we can’t be sure exactly what is going on in these diseases in terms of the barrier function of your intestine. As the science stands now, “Leaky Gut Syndrome” is more likely a symptom of other problems than a disease in itself. However, it does seem pretty likely that all of these conditions have something in common: a role for the gut microbiota.
Firstly, the gut microbiota help prevent “bad bacteria” from getting access to the cells of your gut. These good bacteria accomplish this by simply taking up space and resources so that “bad bacteria” can’t survive. In addition, the good bacteria eat up food in your intestine, break it down, and poop out its subcomponents, which are actually nutrients that you need to survive. Some of these bacteria-poop-nutrients are needed for your intestinal cells to keep doing their job as a barrier.
Secondly, gut microbiota help train the intestinal immune system, so that it can respond to overgrowth of good bacteria, which can be bad for your health, as well as the presence of bad bacteria. By studying mice raised with absolutely NO bacteria in their intestines, termed “germ-free mice”, scientists have discovered that being raised without gut microbiota is bad news for your immune system. These super-clean mice don’t respond as well as normal to infection with certain “bad bacteria”. Germ-free mice also have fewer immune cells that are responsible for making sure that the immune system has a good balance of inflammation. Too much inflammation or an over-active immune system is no good, and can lead to autoimmune diseases, for example. In contrast, the result of too little inflammation, or an under-active immune system, can be seen in patients with untreated HIV/AIDS: they have lots of infections, and don’t recover well from them. Interestingly, scientists now think that these regulatory immune cells, which are partially trained by the bacteria in the gut, are very important for many of the conditions that “Leaky Gut Syndrome” has been linked to.
So, what is the take-home message from today's post? You really are what you eat! And, if you want to feel good, it's not a bad idea to use food as thy medicine.
Until next time, eat your greens! And, of course, thanks to Denis for the question behind the post.
~ Alex