When you’re happy, your gut is happy. When your gut is happy, you’re happy.
But when you’re stressed, your gut is also stressed. And when your gut is stressed, you feel stressed.
How are they so intricately related, you may ask? Well its because your gut has its own nervous system (enteric nervous system) that communicates directly with your brain (central nervous system). In embryology, one neural tube differentiates into the brain in your head and the brain in your gut. Both are richly innervated with cells and nerves that communicate with neurotransmitters and hormones and provide the basis for the Brain-Gut Axis. This bidirectional system translates feelings, thoughts and memories from your brain into neurotransmitters that are released and affect your gut motor, immune, and inflammatory function and vice versa.
So, what exactly does STRESS do to the GUT?
· Increases pain
o Being upset/distressed à abdominal discomfort, change in bowel function
o Stress lowers the pain threshold so it takes less stimulus to cause pain, especially in IBS
· Messes up your pooping ritual
o Anger, intense pleasure, or aggressive behavior à more blood flow to gut, diarrhea, especially in setting of functional GI disorders
o Fear or depression, withdrawal (giving-up), or disengagement à less blood flow to gut, constipation
· Causes massive inflammation
o Stress increases proinflammatory cytokines
o Acute stress triggers the hypothalamic-pituitary axis, leading to increased cortisol and activates the autonomic nervous system, with increases in proinflammatory cytokines
· Causes leaky gut
o Stress leads to mucosal permeability due to weakening of tight junctions, with an increase in bacterial translocation into the intestinal wall
· Destroys your microbiome
o Stress can lead to a change in intestinal microflora, with a shift from “good” to “bad” bacteria
And how does your GUT affect your MIND and STRESS?
· Gut infection (gastritis, colitis) causes stress-induced memory problems
with decreased neuronal activation in the hippocampus
o Memory impairment persists after bacterial clearance
o Probiotics prevent stress-induced memory deficits, normalizing the hypothalamic-pituitary-adrenal axis and colon injury.
o Lab animals raised in a sterile environment with a germ-free gut had an exaggerated hypothalamic-pituitary-adrenal axis activity with elevated cortisol and anxiety in response to stress
o Colonization with bacteria (ex. Bifidobacterium) and probiotics reduced the stress-induced increase in cortisol and anxiety
o Lactobacillus reduced stress-induced cortisol levels, an effect that was abolished with vagotomy, suggesting that a functional neural relay from gut to brain is necessary for governing stress response
· Intestinal inflammation leads to depression/psychiatric disorders via cytokines
o Chronic inflammatory diseases such as IBD (Crohns, Ulcerative colitis) are associated with fatigue, anorexia, depression and “sickness behavior”, due to peripheral cytokine activation that produces central effects
o Depressed patients with increased inflammatory biomarkers are less likely to respond to treatment
o Inhibiting proinflammatory cytokines may improve depression and increase treatment response
What can you do?
1. Eat a lot of fiber and a gut-healthy diet to diversify your microbiome
2. Build a large, strong social-support network full of family, friends, co-workers, etc.
3. Know how to cope with stress! See a therapist, do a ton of yoga, meditate, exercise
4. Read Robert M. Sapolsky’s incredible book, “Why Zebras Don't Get Ulcers: The Acclaimed Guide to Stress, Stress-Related Diseases, and Coping”
[gut facts adapted from Sleisenger and Fordtran’s Gastrointestinal and Liver Disease, 10th edition]