Connections between the Brain and the Gut
Gut, Emotions and the Brain
- If you’ve ever had your stomach in knots before speaking in public, then you know the gut listens carefully to the brain. According to William
Whitehead, PhD, a professor of medicine and an adjunct professor of psychology at the University of North Carolina, the entire digestive system is closely attuned to a person’s emotions and state of mind. People with irritable bowel syndrome often suffer symptoms during times of stress and anxiety, and even perfectly healthy people can have an increase of stomach pain, nausea, constipation or diarrhoea during stressful life events.
- The gut has a mind of its own, the "enteric nervous system". Just like the larger brain in the head, researchers say, this system sends and receives impulses, records experiences and respond to emotions. Its nerve cells are bathed and influenced by the same neurotransmitters. The gut can upset the brain just as the brain can upset the gut.
- In evolutionary terms, it makes sense that the body has two brains, said Dr. David Wingate, a professor of gastrointestinal science at the University of London and a consultant at Royal London Hospital. "The first nervous systems were in tubular animals that stuck to rocks and waited for food to pass by," according to Dr. Wingate. The limbic system is often referred to as the "reptile brain." "As life evolved, animals needed a more complex brain for finding food and sex and so developed a central nervous system. But the gut's nervous system was too important to put inside the newborn head with long connections going down to the body," says Wingate. Offspring need to eat and digest food at birth. Therefore, nature seems to have preserved the enteric nervous system as an independent circuit inside higher animals. It is only loosely connected to the central nervous system and can mostly function alone, without instructions from topside.
- In recent years, the link between the nervous system and the digestive system has been recognized. There is a constant exchange of chemicals and electrical messages between the two systems. In fact, many scientists often refer to them as one entity – the brain-gut axis. Therefore, what affects the bowel will directly affect the brain and vice versa.
- Medications designed to target the brain can also cause nausea, diarrhoea, constipation or abdominal upset because the body actually has two brains – one encased in the skull, and a lesser known but vitally important one found in the human gut. Fat-soluble drugs penetrate the gut wall, thus injuring the natural balance of the digestive system. Antidepressants, benzodiazepines and sleeping pills are fat-soluble.
SSRIs (Selective Serotonin Reuptake Inhibitors) are believed to ease depression by enhancing levels of Serotonin to the brain. But 95% of the Serotonin in the body lies in the digestive system, and diverting the supplies of Serotonin can increase anxiety, alter sleep patterns and cause sexual dysfunction as well as adversely affect the cardiovascular region. Balancing the hotbed of Serotonin production in the gut is critical to restoring the balance. Some scientists believe that SSRIs boost Serotonin in the gut and change the signals to the brain, since antidepressants prevent the uptake of Serotonin by cells that should be using it. But Serotonin is calming to the digestive tract. This helps to explain why a large percentage of people experience nausea, stomach upset, constipation and diarrhoea, which in turn can cause depression, anxiety, insomnia and fluctuations in appetite.
- The question has been raised: Why does the human gut contain receptors for benzodiazepine, a drug that relieves anxiety? This suggests that the body produces its own internal source of the drug. According to Dr. Anthony Basile, a neurochemist in the Neuroscience Laboratory at the National Institutes of Health in Bethesda, MD, an Italian scientist made a startling discovery. Patients with liver failure fall into a deep coma. The coma can be reversed, in minutes, by giving the patient a drug that blocks benzodiazepine. When the liver fails, substances usually broken down by the liver get to the brain. Some are bad, like ammonia and mercaptan, which are "smelly compounds that skunks spray on you," says Dr. Basile. But a series of compounds are also identical to benzodiazepine. "We don't know if they come from the gut itself, from bacteria in the gut or from food, but when the liver fails, the gut's benzodiazepine goes straight to the brain, knocking the patient unconscious, says Dr. Basile.
The payoff for exploring gut and head brain interactions is enormous. Many people are allergic to certain foods like shellfish. This is because mast cells in the gut mysteriously become sensitized to antigens in the food. The next time the antigen shows up in the gut, the mast cells call up a program, releasing chemical modulators that try to eliminate the threat. The allergic person gets diarrhoea and cramps. Many autoimmune diseases like Krohn's disease and ulcerative colitis may involve the gut's brain. - Author of "The Second Brain" Dr. Michael Gershon, a professor at New York City's Columbia-Presbyterian Medical Center, tells a story about an old Army sergeant, a male nurse in charge of a group of paraplegics. With their lower spinal cords destroyed, the patients would get impacted. "At 10am every morning, the patients got enemas. Then the sergeant was rotated off the ward. His replacement decided to give enemas only after compactions occurred. But at 10 the next morning everyone on the ward had a bowel movement at the same time, without enemas." Had the sergeant trained those colons? The human gut has long been seen as a repository of good and bad feelings. Perhaps emotional states from the head's brain are mirrored in the gut's brain, where they are felt by those who pay attention to them?