Anyone who has ever had a presentation, important meeting or otherwise nervous situation will know that the digestive system also experiences your stress. Nausea, vomiting, and diarrhea are common symptoms of what your mind is thinking. But does it go further then this? How intimately tied is your digestive system to your mind and what are the implications on your health?
Studies have shown that individuals suffering with mental disorders have twice the risk of having a digestive illness. This creates a vicious cycle whereby anxiety leads to digestive upset, which leads to further anxiety. Anxiety, depression, irritable bowel syndrome and ulcers have symptoms that manifest in both the brain and gut.
The relationship between the mind and digestive system is clear when evaluating irritable bowel syndrome. As a “functional” disease IBS is not caused by a structural abnormality, but the symptoms of chronic abdominal pain, and diarrhea alternating with constipation are undeniably linked to its other symptom—anxiety. The gut is often called “the second brain” because the brain molecules and receptors that effect our mood and mental health are also present in the gut.
Up to 90% of the body’s serotonin, our “feel good” brain chemical, is housed in the gut where it activates serotonin receptors. Patients with diarrhea-prominent IBS secrete higher amounts of serotonin after a meal and those with constipation secrete lower amounts when compared to normal controls. The serotonin nerve cell signaling is involved in gut motility, sensitivity and digestive fluid secretions, implicating its involvement in the pain and extreme bowel irregularity of IBS.
A fascinating area of research focuses on the effects that commensal bacteria have on our mind. The digestive system is inhabited with 1X1013 to 1X1014 microorganisms or gut flora, more than 10 times the number of human cells in our bodies. While the gut flora is being established in the first year of life, negative consequences arise when the infant experiences stress—stress lowers and causes an imbalance in gut flora that has a lasting effect on digestive and mental health.
Research on animal models demonstrates that growing in a germ-free environment (no gut flora) leads to an increased stress response, as well as risky behavior and deficits in memory. Imbalances in commensal flora, caused by bacterial infections, leads to increased anxiety. A recent study demonstrated that re-establishing gut flora with probiotics causes changes in brain regions that lead to positive effects on emotion and cognition.
Research looking more deeply into the relationship between the mind and digestive system is ongoing, with the results thus far fascinating. This intimate connection proves the importance of adequate nutrition and stress reduction for mental health.