The smart stomach

It’s a proven fact: The gut ‘talks’ to our brain. What the discovery means for our overall well-being.


 “Butterflies in my stomach.” “My stomach is in knots.” “I feel it in my gut.”

These common expressions link emotions to the digestive system, but now we know there’s an actual scientific connection.  When your gut speaks, your brain listens, and vice versa.

Doctor Michael Gershon, a neurobiologist at Columbia University in New York, was the first to suggest, in the late 1990s, that this obscure part of our anatomy acted like a second brain. The gut makes certain decisions on its own and manufactures its own nerve cells.

The intestine and brain communicate via the vagus nerve, a long cord that extends from the base of the cranium all the way down to the abdomen. “We now know that 90 percent of the messages travelling along this nerve originate in the intestine,” says Gershon. “The gut speaks, and the brain listens.”

In researchers’ view, the digestive system influences a person’s vitality. They even argue that anxiety and depression originate in the intestine. This is far from impossible when you consider that 95 percent of body’s serotonin, a neurotransmitter that plays an important role in regulating mood, resides in our “plumbing.”  

“At the University of California, we replaced electroconvulsive therapy with vagus nerve stimulation to treat depression and epilepsy,” Gershon adds. And it works. There’s more: with the new treatment, they noticed that subjects’ memory and learning ability also improved.

Other scientists have reached similar conclusions by studying intestinal flora, the layer of some 100 billion “good” bacteria that lines the walls of the intestine. After discovering the extent of the role these flora play, they now consider them an organ in their own right and have renamed them “microbiota.” It’s quite a promotion; one that speaks volumes on the relationship between the gut and mental health.

Another pioneer in the field, American gastroenterologist Emeran Mayer, is examining the links between a person’s brain, microbiota and state of mind. “We already know that certain sensations, such as nausea, hunger, satiety and fatigue, originate in the intestine. We’re now trying to demonstrate that the reaction of people subjected to emotional stimuli can be influenced by the presence of probiotics, microorganisms that are useful for intestinal health,” explains the professor in the departments of medicine, physiology, psychiatry and behavioral sciences at the University of California, Los Angeles (UCLA). In other words, a digestive system in good health due to probiotics can influence a person’s mood.  

Evidence has already emerged from studies with rodents. Researchers at University College Cork in Ireland gave probiotics to a group of mice for six weeks. The result: those that ingested the probiotics were more adventurous than those that didn’t. When their brains were examined, it was found that their level of corticosterone, the hormone linked to stress, was lower than that of the other mice.  

Doctor Mayer is conducting a similar experiment on humans. Will he reach the same conclusion: a healthy stomach leads to a healthy mind? It’s too early to tell, but the researcher seems optimistic.  

At the Université de Montréal, a pharmacology research laboratory led by Dr. Guy Rousseau made a discovery that confirms this hypothesis. It is known that many patients who suffer a heart attack go on to exhibit symptoms of depression. Sure enough, this pathology in rats was treated with probiotics, and the results were encouraging. True, the test subjects were mere rodents. But perhaps one day soon, we’ll start to see real benefits for humans.
In the meantime, wouldn’t the best strategy to beat the “blues” be to watch what we eat? It’s quite likely that greasy fries and hamburgers negatively affect our mental state. Need more evidence? Try this: after following 9,000 people for close to six months, researchers at the University of Las Palmas de Gran Canaria in the Canary Islands came to the conclusion that the more junk food people ate, the more they were susceptible to bouts of depression.

For more information, visit the Canadian Digestive Health website.