Have you ever been hangry—that is, hungry and angry at the same time? I know I have. It’s just one of the many ways our gut can affect how we feel. However, it can be much more complex than needing food instantly. Our digestive system influences us in a vast number of ways with a large percentage of people suffering from IBS – Irritable Bowel Syndrome, which is often a blanket statement saying we don’t know what’s wrong with you; it’s all in your head!
Our gut can have huge implications on how we function but there is much, much more to it. There are a whole host of bacteria living in you as we speak. I’ve always thought that my mind and body were independent of the organisms hanging out inside me. In Giulia Enders’ brilliant book , Gut: The Inside Story of Our Body’s Most Underrated Organ, she explores the many facets of the gut and their implications, including the influences of these bacteria.
Experiments have been done by teams led by John Cryan, showing that the connection between our mind and gut isn’t as simple as you’d think. Those other organisms can change how we feel and act. In an experiment looking at motivation and depression, a mouse was placed in a small container that was too deep for its feet to touch the bottom. This caused the mouse to fruitlessly swim around looking for dry land. The length of time the mouse swam would be predicted by its tendencies toward depression. It would swim a little and then freeze, accepting its destiny.
Depressed people have less motivation to live which isn’t a surprise, but here’s what was:
Afterwards, researchers decided to change the gut ecosystem of the mice. Half were given Lactobacillus rhamnosus (JB-1), normally known to benefit the gut. With that change, they swam longer and had less stress hormones in their blood. Memory and learning test results were better too! The vagus nerve, cranial nerve X, is the main highway through which signals from the gut are relayed to the brain. It is involved in heartbeat regulation and breathing, but also, notably, for digestion. It controls the muscle fibers which help contract stomach muscles to push food into your small intestine. Nerve fibers extend all the way to the second part of the transverse colon while also influencing the enzyme levels and digestion of nutrients.
The Vagus Nerve and the Digestive System. Image taken from http://www.bloomholisticretreats.com/wp-content/uploads/vagus-nerve.png
When researchers subsequently severed this vital component, those benefits all disappeared.
So, what about humans? Well, IBS is characterized by bloating, diarrhea, and constipation, revealing higher rates of anxiety and depression. This the result of a myriad of factors: there may be bacteria in the gut that are harmful, people may have a particular food intolerance, and minor inflammations could occur, among others. I’ve met many people including patients, friends, and family that have issues with their gut. Many have not found a treatment that works and fight their whole lives with each and every meal.
The bacteria in our gut can heavily influence us and when something doesn’t work, then people often get resigned to that lifestyle. I’ve known people who just wouldn’t accept a simple diagnosis. In one example almost everything caused abdominal bloating and pain—sometimes without eating anything! Then, when one doctor explicitly said they had IBS, that was it; no more discussion! The doctor said they were certain, but guess what? Their suspicion that it was something else was confirmed when a SIBO—that’s Small Intestinal Bacterial Overgrowth—test was taken.
It’s estimated that 40-85% of people who have IBS also have SIBO when taking a breath test. For the test, a special kit has to be ordered (it’s a bit pricey at around 300 dollars). With ongoing treatment, symptoms greatly improved. So, knowing more about the gut and more specifics about the problem can help immensely. The blanket of IBS diagnosis isn’t the be-all and end-all. Indeed, the gut is more sophisticated than once thought. But how can the gut change its own environment and if so, what lives there to make this possible?
Find out more about SIBO here:
http://www.mindbodygreen.com/0-11020/10-signs-you-have-small-intestinal-bacterial-overgrowth-sibo.html
I’m sure we all know people whose eating habits are dictated by stress. Stress on the body means energy and blood flow will be taken elsewhere where it is needed. According to one main theory, less blood supply and weaker gut tissue could let various bacteria survive there that normally wouldn’t. Furthermore, one period of severe stress can affect you long afterwards. Stressing people out during mealtimes is a surefire way to make it worse! In fact, having strict rules while eating could easily increase stress and thus alter the bacteria that live there. As I’ve just mentioned, an overgrowth can cause SIBO, but what else can changing the biodiversity do?
At McMaster University, two different strains of mice were investigated for behavioral changes after changes to their bacterial flora. They destroyed the gut bacteria of both strains with antibiotics and replaced their bacteria with another strain. Where strain BALB/c is shy and complacent, strain NIH is more outgoing and adventurous. Fascinatingly, the personalities subsequently switched along with the bacteria! I am curious to know what parts of my personality would switch if I switched my gut’s bacteria. Hopefully not all of them! That might be a bit depressing.
There are mice that have no bacteria at all, and the effects of bacteria on these mice is showing us that our gut can potentially have an enormous influence on other aspects – not just personality. Bacteria from obese humans have been given to them and they gain weight much more easily than if they were given them from people with normal weight. In fact, you can tell if someone is obese by looking at their bacteria with up to 90% accuracy, as opposed to comparing their entire human genomes, in which case prediction goes down to a mere 60%! That means that your bacteria may influence your health conditions much more than our DNA – which we generally hold as essential to defining our humanity.
One last aspect is the influence on our basic ability to be healthy. You can wash your hands and isolate yourself from germs but that might not be enough. The immense numbers of bacteria and their composition can heavily dictate your health outcomes. Bacteria in a healthy adult human can be around 3 pounds with roughly one hundred trillion bacteria. Our immune system being 80 % in the gut, it must determine whether what it encounters is our human cells or foreign bacteria that may or may not have to be eliminated. The composition of this ecosystem can have far-reaching implications. Take a look at this TED talk.
In terms of the variety and distribution of microbes living in you, they initially depend heavily on how you were born: either by a natural birth or a Cesarean section. Babies born through the birth canal tend to have bacteria reflecting the bacteria there and ones born by Cesarean section tend to have ecosystems dominated by skin bacteria. These babies born by Cesarean section tend to risk having more allergies or asthma. It can take many months for them to create a normal gut ecosystem. Studies with giving the birth canal bacteria to newborns born by Cesarean are being done to see if it can solve this issue.
We’re slowly learning that there is a lot more to our gut. It can influence us more than I would have ever thought possible, with the flora being responsible for future health outcomes as well as personality. The degree of this on humans still remains to be seen. However, one thing is for certain: it is a huge part of our lives and once we learn more, it may have the potential to treat a range of diseases.