Mark Babyatsky, MD, chair of the department of medicine at Mount Sinai, in New York City Dietary fiber, found particularly in vegetables, fruits, beans, and whole grains, helps to keep bowel movements regular. Individuals who consume high-fiber diets have much lower rates of constipation than individuals that eat a low-fiber diet, plus they have fewer hemorrhoids and diverticula (outpouchings) in the colon. Too much fiber may result in loose stools, bloating, or even diarrhea. Kenneth Brown, MD, gastroenterologist Dietary fiber is the term used to describe the combination of both insoluble and soluble fibers. Soluble fiber is the form of fiber that dissolves in water. Examples of foods that contain soluble fiber include fruits, oats, legumes and barley. Insoluble fiber comes from plant cell walls and does not dissolve in water. Examples of foods that contain insoluble fiber include wheat, vegetables, and seeds. Fiber works by both bulking up the stool and retaining water. In addition, bacteria help digest the fiber which produces healthy ingredients for the colon such as short chain fatty acids. Fiber can be beneficial for both diarrhea and constipation depending how much fluid is also taken in with the fiber. Fiber can actually become a constipating agent if the amount of fluid taken in is too low. Lisa Ganjhu, DO, gastroenterologist Fiber plays a major role in digestive health. Fiber is the fuel the colon cells use to keep them healthy. Fiber also helps to keep the digestive tract flowing, by keeping your bowel movements soft and regular. It is possible to get too much fiber, and your body will know it. You may experience bloating and many more bowel movements than you are normally are used to. Jo Ann Hattner, MPH, RD Fibers are primarily non-digestible carbohydrates. Fibers are components of plant foods, fruits, vegetables, dried beans and peas, lentils, nuts, and seeds — any food that is classified as a plant. The fiber provides structure. Think of the celery stalk and the obvious vertical fiber strings that one often gets caught in their teeth. In addition, because fibers are non-digestible, they contribute to stool bulk and add form to the stool. People with irregularity are often advised to increase their fiber and fluid intake. But can you get too much? Well yes, you can get too much of anything. But you will know when you do. When you eat too much fiber, your digestive system may be overwhelmed and you will suffer from abdominal bloating and pass excessive gas. You don’t want that, so keep an open mind and just eat as much fiber as you personally need to keep regular and enjoy a flat abdomen. Another really important role of fiber is that some fibers are prebiotics — meaning they are fermented in the colon by the healthful beneficial bacteria. The products of this fermentation, which include short chained fatty acids, are thought to be healthful to the lining of the colon. In addition the acidic milieu that results from the fermentation is unfriendly to the survival of the pathogenic (harmful) bacteria which cause illness and may contribute to an unhealthy colonic environment. Expect more research findings on this subject. Lisa Pichney, MD, gastroenterologist Fiber is good for the gastrointestinal tract because it provides bulk to the stool, helping in colonic lubrication and transit. Too much fiber can result in unwanted gas production. Seth Rosen, MD, gastroenterologist A high-fiber diet can contribute greatly to gastrointestinal health as well as to a general healthy lifestyle. Fiber helps to regulate bowel movements so they are not too loose or too hard and may decrease the risk of diverticulosis and diverticulitis. Most high-fiber foods tend to be low in calories, sugar, and fat, so they are generally healthy. When eating high-fiber foods one may feel fuller and thereby less inclined to overeat. Additionally, high-fiber diets are often part of a low-cholesterol, heart-healthy diet. While it is rare for most of us to exceed the recommended daily fiber intake, some people do have difficulty with gas and bloating when eating a large amount of fiber or introducing fiber too quickly into the diet. Also, keep in mind, eating fiber always requires adequate hydration and help to minimize the gas and bloating that may develop. Sutha Sachar, MD, gastroenterologist A diet high in fiber has repeatedly shown benefits in preventing colon cancer. Contrary to what many people think, soluble fiber can be used for treatment of diarrhea as well as constipation. The only drawback to eating “too much fiber” is that is can cause gas. This can usually be overcome by drinking plenty of water along with it. Contrary to conventional (mis)understanding, its role in assisting constipation is perhaps its least important. Its most important benefit is as a source of nutrition for the bacterial culture that makes up the mucosal lining, thus maintaining it. Subsequently the mucosal lining protects the gastrointestinal wall, which may prevent inflammatory diseases such as irritable bowel syndrome, colitis, and Crohn’s disease. A common cause of constipation is a magnesium deficiency. If you do not address that first, the fiber is likely to just back up on you. Rule number one: If you have any kind of inflammatory bowel disease such as IBS, colitis, leaky gut, etc. do not take any kind of bowel cleanser or fiber supplement — you will definitely make you problem worse. William Chey, MD, gastroenterologist Fiber helps to regulate water content in the stool. If stool is too dry, fiber tends to retain fluid and soften stool. If stool is too runny, fiber can absorb water and add form to the stool. Taking additional fiber can also impact of blood cholesterol levels. The typical western diet contains [too little] fiber per day. To improve constipation-related symptoms, people should consume 20 to 25 grams of fiber per day. Eating too much fiber can lead to problems with cramping, bloating, diarrhea, or constipation. When starting fiber, it is best to “start low and go slow.” Increasing the amount of fiber in your diet too quickly (days as opposed to weeks) can lead to the development of unwanted side effects. Jacqueline Wolf, MD, gastroenterologist Fiber is plant material that can’t be digested by the small intestine. Soluble fiber (can be dissolved in water) passes through the small intestine relatively unchanged until it reaches the colon (large intestine) where the bacteria can ferment or digest the fiber. The products of the fermentation stimulate the bowels, cause retained water in the stool and bulk up the stool. Insoluble fiber passes through the colon relatively unchanged and helps bulk the stool. A combination of soluble and insoluble fiber helps maintain normal intestinal function by affecting the consistency of the stool and affecting digestion of other substances. Fiber may cause gas and bloating in some people and this may be a function of the amount or the type of fiber. In addition, in some people fiber may make the constipation or the symptoms of irritable bowel syndrome worse. In a person with a narrowing in the intestine, for example from Crohn’s disease, insoluble fiber could make that person more at risk for a blockage of the bowel.
