The Brain-Gut Connection

Fast Facts About the Gut

Your gastrointestinal tract is home to a diverse world of microorganisms, neurotransmitter chemicals, and nerve cells. You already know that the gut is responsible for digestion, but mounting research has made it clear that there’s a link between the intestinal tract and processes that occur in the brain. Imagine the feeling of “butterflies in your stomach” when you feel nervous - the gastrointestinal tract responds to your emotions. But this process also works the other way around: your emotions and mental state can impact what’s happening in your gut.

How Is the Gut Connected to One’s Emotions and Mental State?

The gut is lined by its own nervous system, called the enteric nervous system (ENS). Scientists refer to the ENS as the “little brain,” but it’s anything but little. The ENS is actually the largest part of the autonomic nervous system — the part of the body’s nervous system that runs automatically and controls processes like digestion, blood pressure, and breathing — and can operate independently of the central nervous system (CNS). The ENS and the CNS communicate with each other to form the gut-brain axis (the neural interaction that links the emotional and thinking centers of the brain with the intestinal tract and its functions). Moreover, the gut microbiome (the bacteria and other microorganisms that live in the gut) and the gut-brain axis also communicate with each other, linking the health of your gut microbiota to your cognitive and emotional state.

Why Is the Gut Microbiome Important for Your Health?

The gastrointestinal tract has many responsibilities that are crucial to your overall well-being. Digestion. The primary role of the gut is digestion, which ultimately is the absorption of nutrients and water to support all of your body’s functions. Both muscle movements (like swallowing) and blood flow, which facilitates nutrient absorption by the body’s cells, are essential to digestion.

Immune system. The gut contains almost 70 percent of the body’s immune system. Some scientists speculate that the increase in autoimmune disease and inflammatory conditions in first-world societies stems from a lack of diversity in gut microorganisms due to changes in diet, as well as overuse of antibiotics and cleaning and disinfecting products.

Brain health. Studies have linked certain disorders of the brain, like Alzheimer’s disease, schizophrenia, and Parkinson’s disease, to a disruption in the gut microbiota.

Mental health. Certain gut microbes have been shown to contribute to the onset of symptoms of anxiety. This may explain why people diagnosed with irritable bowel syndrome (IBS) are more likely to suffer from anxiety and depression than people without IBS. To further exacerbate things, anxiety can also worsen symptoms of IBS.

How Can You Maintain the Integrity of Your Gut Microbial Health?

Maintaining a diverse and balanced gut microbiota is important for overall health. Below, we provide you with some suggestions on how to keep your gut healthy.

Find ways to manage and lower stress levels. When you’re stressed, you may feel one of many effects, like anxiety and headaches. What you may not notice is the change happening in your gut. A study conducted on mice in 2011 found that, when mice were exposed to stress, the communities of bacteria in the gut were significantly compromised: there was less diversity in the types of bacteria present, and an increase in harmful bacteria. Try lowering your stress levels with activities like meditation, spending time with friends and family, and exercise to help keep your gut microbiome balanced. (And if you find that these activities don’t help you control your stress levels, consider speaking with your general practitioner.)

Refrain from overusing antibiotics. Antibiotics are an important treatment for many different types of infections, including some life-threatening ones. But when overused, they can significantly deplete the good bacteria in the gut, leaving it vulnerable to changes in the mucosal membrane and an overgrowth of unhealthy bacteria, like yeast or candida.

Many patients see their doctor with a minor ailment, like a cold, and request antibiotics. If your doctor opts not to prescribe an antibiotic, understand that this is often because it may not be necessary or helpful. (Colds, for example, are often caused by viruses and would not respond to antibiotics anyway.) Your physician has your health and your best interests at heart when he or she recommends a non-antibiotic treatment.

Eat foods that contain probiotics. Probiotics are live cultures of bacteria that are similar to those found in the gut. When consumed, they add to the population of bacteria that are already inhabiting your gut. Foods and drinks that include probiotic bacteria include:

  • Yogurt (look for containers labeled with “contains live active cultures”)
  • Kimchi
  • Sauerkraut
  • Miso soup
  • Kombucha

Probiotic dietary supplements, which typically come in pill form, also get a lot of attention in the media these days. Try including more probiotic foods in your diet to start, and speak with your gastroenterologist about whether you could benefit from supplements.

Eat foods that contain prebiotics. Prebiotics are indigestible carbohydrates, like fiber, that contain nutrients for the healthy bacteria in your gut to grow. Prebiotics are found in high-fiber foods, as well as certain fruits and vegetables. Your body cannot break down prebiotics. Instead, these substances are passed through the small intestine and then fermented (broken down and “eaten” by healthy bacteria) in the large intestine.

Examples of prebiotic foods include:

  • Bananas
  • Beans
  • Garlic
  • Oatmeal
  • Onion
  • Jerusalem artichoke (a root vegetable, also called sunchoke or sunroot)
  • Whole grains
  • Yams

For individuals with irritable bowel syndrome, prebiotics may exacerbate IBS symptoms, and many prebiotic foods don’t fit into a FODMAP diet plan. For sensitive patients, fermentation of prebiotics in the large intestine can lead to bloating, diarrhea, or constipation. If you have a history of IBS, talk to your gastroenterologist about prebiotic food options and whether a diet rich in prebiotics is right for you.

Ongoing Research Contributes to the Discovery of New Treatments

The relationship between the gut and the brain have opened the doors to exploring new treatments for both mental and psychoneurotic disorders, as well as disorders of the gastrointestinal tract. For example, your gastroenterologist may prescribe you antidepressant medications if you have irritable bowel syndrome. These medications can interact with nerves in the gut to relieve symptoms of IBS.

Research is still ongoing in this area. In addition to continuing to understand the relationship between mental health and the gut microbiota, scientists are interested in exploring the relationship between gut microbiota and cognitive function, such as memory and concentration. But there’s clearly a strong link between the brain and gut health.