Your Gut Feeling: A Healthier Digestive System Means a Healthier You

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Nervous. Queasy. Butterflies. We have all heard these terms used to describe our "gut feeling" when we’re anxious or stressed. But how does our gut know and react to what we’re thinking and feeling? According to Dr. Lisa Ganjhu, clinical assistant professor of medicine at NYU Langone Medical Center, the gastrointestinal system is more than the body’s primary site of taking in and absorbing nutrients. This system of critical digestive organs also acts as a type of switchboard or communication center to and from the brain, and functions as one of the body’s frontlines in the fight against disease. “Our gut plays a major role, not only in our gastrointestinal health, but in the health and well-being of the entire body,” Dr. Ganjhu said.

Building Blocks for a Healthy You

The gastrointestinal system, also referred to as the gastrointestinal tract, digestive system, digestive tract, or gut, is a group of organs that includes the mouth, esophagus, stomach, pancreas, liver, gallbladder, small intestine, colon, and rectum. The gut serves many essential roles in sustaining and protecting the overall health and wellness of our bodies, starting with the intake and absorption of nutrients and water. According to Dr. Ganjhu, it is this digestive process that provides the building blocks the body needs to live, to function, and to stay healthy.

Mouth. The digestive process begins with the mouth, where the teeth and tongue help us to chew our food and where chemicals in our saliva, called enzymes, start to break down the food.

Esophagus. The chewed food then enters the esophagus, or food pipe, which uses its muscles to move the food from the mouth to the stomach through a coordinated process called peristalsis. The esophagus then releases the food into the stomach and a valve, or sphincter, acts as a gateway to keep the food from going back up into the esophagus.

Stomach. In the stomach, our food is sterilized and further broken down. The stomach produces hydrochloric acid (HCL), which helps to sterilize the food, so that it doesn’t give us an infection or make us sick. The stomach’s enzymes play a significant role in digesting proteins and other nutrients, while the organ’s churning motion helps to turn the now mushed-up food into a liquid, called chyme. This process often takes hours, with heavy and fatty meals taking longer to digest than lighter meals. When the gut and brain have “talked” and decide the food is ready, the stomach moves the liquefied food into the small intestine.

Small intestine. The small intestine is where the nutrients are absorbed and packaged to the rest of the body, to make the building blocks necessary to keep the human body alive and healthy. “The massive absorption of nutrients that occurs in the small intestine requires a large surface area. Even though it is called the small intestine, it is a very long organ, measuring approximately 21 feet when stretched out, with its inner lining having little hair-like projections, called villi, and functioning much like a towel to increase the surface area for absorption,” Dr. Gahjhu noted.

Pancreas, liver, gallbladder. Along the way, the pancreas, liver, gallbladder, and bile duct also play important roles in our digestive process. The pancreas secretes digestive enzymes into the small intestine to help break down proteins, carbohydrates, and fats, while also producing the hormones insulin and glucagon to help regulate our blood sugar. The liver, which is the largest solid organ in the body, is the body’s primary site of protein building. The liver produces a green liquid, called bile, which is secreted into the gallbladder, which when needed releases the bile into the small intestine to help break down dietary fats. In turn, the small intestine sends carbohydrates, fats, and other nutrients to the liver, where they are converted into protein and glucose, to be used as fuel for the body.

Colon and rectum. When the small intestine is finished absorbing nutrients from the liquefied food, the remaining digestive material is passed into the colon. The colon acts as the gut’s “dryer,” absorbing water and electrolytes as nourishment and passing any remaining solid waste to the rectum and out of the body.

Communication Center for the Brain

According to Dr. Ganjhu, the gut serves as a communication center for the brain, not only to ensure optimal digestion but also other important health functions. “I often refer to the brain as a part of the gastrointestinal system, because the brain and gut are in constant communication,” she said.

First, the gut provides information to the brain, while the brain helps us decide what, when, how much, and how fast to eat and drink. “The gut and brain work together in the digestive process. For example, when we have had a particularly fatty meal, the gut and brain will talk and decide to hold that food in the stomach a little longer than for a lighter meal. Only when the food has been broken down sufficiently will it be sent to the small intestine,” Dr. Gahjhu explained.

In addition, both the brain and gut play key roles in our stress level, and our mood or state of mind. The gut may inform the brain of a stressor, and the brain will do the same for the gut. Not only is the gut filled with nerve cells that receive and provide information to the brain, but the gut also produces more than 90% of the body’s serotonin, a hormone that helps regulate our mood or emotions. “As we might imagine, stress can result in adverse effects on the gastrointestinal tract and the whole body. Stress can cause chronic nausea or bloating, and can be a trigger for disease flares or exacerbation of symptoms in people who have irritable bowel syndrome, inflammatory bowel syndrome, and other gastrointestinal conditions,” Dr. Ganjhu said.

Frontlines of Fighting Disease

The gut is one of the core disease-fighting systems of the human body. First, the acid and enzymes in the stomach work to sterilize our food and, in this way, protect the body from illness and infection. In addition, the digestive tract is an important source of immune function in the body. “All foods we eat are in communication with immune receptors in the digestive tract, triggering hormones and various cell types that help the body with its immune function,” Dr. Ganjhu explained.

One way the gut aids in immune function is through the presence of Peyer’s patches, or large oval clusters or nodules of lymphoid tissue that are found on the wall of the small intestine. “Because the lining of the gastrointestinal tract is exposed to the external environment, through food and other material, bad bacteria or other pathogenic substances can gain entry into the gut. Peyer’s patches help to monitor the lining of the gut and, when necessary, generate an immune response, producing antibodies that will fight rogue antigens and allergy-causing substances,” said Dr. Ganjhu.

Finally, the digestive system is the home of the “gut microbiome”—a diverse community of different bacteria types that play a vital role in both fighting disease and maintaining our health. Each of us has his or her own unique bacteria mix, or bacteria “thumbprint” in the gut. Some gut bacteria, or some bacteria in excessive amounts, can cause infection, symptoms, and even an increased risk for cancer. While other bacteria, or the right amounts of these bacteria, help us to fight disease and stay healthy. Scientists are continuing to study the good and bad effects of bacteria in the gut, and whether there are mixes of bacteria that correspond to good health and health risks.

NYU Langone researchers recently published a study in the journal Nature, showing a potential association between antibiotic use, changes in gut bacteria, and an increased risk of obesity. In addition, doctors have begun using good bacteria to treat people who have a serious and potentially life-threatening infection, such as Clostridium difficile (C diff) infection, when antibiotic therapy is no longer working.

Tips To Maximize Health & Wellness

“It’s important to do what we can to keep the gut healthy and optimize our overall health and wellness. Overall, eating healthy foods, maintaining an active lifestyle, managing our stress levels, and getting the recommended screening tests can help us maintain a happy gastrointestinal system and to live happy, healthy lives,” Dr. Ganjhu said.

Dr. Ganjhu outlined several steps to help maximize gastrointestinal and overall health and wellness:

Reduce and manage stress. This could mean taking a few minutes for meditation, a relaxation exercise, or time for yourself each day. Avoid the urge to eat “comfort foods” that may not be good for you.

Eat well. Feed your body what it needs to stay healthy. “In general, a healthy diet is one that’s high in fiber, moderate in protein, and low in fat, with minimal processed foods or toxins,” Dr. Ganjhu noted. Dr. Ganjhu recommended whole grains; fresh, bright fruits and vegetables; low-fat dairy; lean meat proteins, such as fish, chicken, and turkey; vegetable proteins such as soy, legumes, and beans; omega-3- rich meals, including fatty fish such as salmon and tuna, sardines, and anchovies. Because of the risk of mercury exposure in fish, smaller fish (sardines and anchovies) are recommended over larger fish, with a maximum of two fish meals per week. Dr. Ganjhu emphasized the importance of staying hydrated with water, green tea, or low-sugar juices and eating enough fiber, which not only keeps the gastrointestinal tract moving, but also nourishes and energizes the cells of the colon. Dr. Ganjhu advised limiting the intake of red and processed meats as well as substances high in sugar, caffeine, or alcohol.

Maintain a healthy body weight. Obesity increases the risk for many diseases, including esophageal, gastric, colon, pancreatic, and other cancers. It also increases the risk for metabolic syndrome, diabetes, fatty liver disease, and other disease. If you’re overweight, talk to your doctor about a weight loss program that is right for you.

Stay active. Maintaining physical activity is important to a healthy gastrointestinal tract, body, and mind. A walk after meals can help to avoid constipation and bloating. In addition, exercise can help reduce the risk of colon cancer. Talk to your doctor about an exercise program that is right for you.

Avoid tobacco. Smoking increases your risk of colon cancer, and a number of other cancers and diseases. If you use tobacco, talk to your doctor about a program to help you quit.

Get screened. “Colon cancer screening is a powerful way to stop cancer before it starts,” Dr. Ganjhu said. Colorectal cancer is the second-leading cause of cancer death in the United States, but it’s highly curable and often preventable with recommended screening and early detection. “A colon polyp or early cancer often causes no symptoms. Screening for colon cancer allows us to find and remove early colon cancers when they are most curable and potentially pre-malignant polyps before they have the chance to turn into cancer,” said Dr. Ganjhu. Men and women at average risk should start screening for colon cancer at age 50. Those with a family history of colon polyps or cancer or certain other risk factors should talk with their doctors about starting screening at a younger age.

Dr. Ganjhu emphasized the importance of seeing a doctor regularly, not only for treatment when we’re feeling ill, but also for prevention when we’re feeling well. “Our doctors are our partners in health and wellness—helping to ensure that we receive the appropriate cancer screenings and identify any emerging issues before they become serious health concerns,” she concluded.

More information about Dr. Lisa Ganjhu