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The irritable bowel syndrome diet is a set of recommendations designed to reduce the symptoms of both constipation and diarrhea that are common with irritable bowel syndrome (IBS). It is not a diet designed for weight loss.
No specific person or organization originated the irritable bowel syndrome diet. Instead, it has developed out of research, observations, and trial and error by gastroenterologists and their patients with IBS.
Irritable bowel syndrome is a disorder in which the intestine (bowel) appears normal, but does not function correctly. The disorder is very common, but its cause is not known. About one of every five Americans has symptoms of IBS, ranging from mild and annoying to severe and lifestyle-altering.
The main symptoms of IBS are pain or discomfort in the abdomen, feeling bloated, having a lot of gas (flatulence), diarrhea, constipation, or alternating periods of both. Symptoms come and go, and over time they can vary in severity in a single individual. Although diet does not cause IBS, certain foods can trigger symptoms. These foods differ from person to person. Common food triggers include alcohol, dairy products, beverages that contain caffeine, and the artificial sweeteners sorbitol and mannitol. The IBS diet is designed to avoid foods that will trigger symptoms and encourage the consumption of foods that help correct diarrhea and constipation and reduce gas.
The function of the irritable bowel syndrome diet is to give the individual more control over his or her symptoms of IBS and thus improve the quality of live.
The challenge of this diet is twofold. First, constipation and diarrhea are opposite in their effect, yet they can appear in the same individual as part of the same disorder. Constipation occurs when food stays in the large intestine (colon) too long. Too much water is reabsorbed into the body, and the stool (waste) in the large intestine becomes hard, dry, and difficult or painful to eliminate. With diarrhea, food moves too quickly through the large intestine. Not enough water is reabsorbed. Stools are loose and watery, and the individual may feel extreme urgency to have a bowel movement.
The second challenge to this diet is that individuals with IBS may respond to the same food in different ways. The IBS diet is not a list of “must eat” and “must not eat” foods, but rather a group of suggested foods that the individual must personalize through trial and error. Keeping a food journal often helps the person with IBS to pinpoint which foods are beneficial and which worsen symptoms.
High-fiber/low-fat IBS diet
Dietary fiber is the collective name for a group of indigestible carbohydrate-based compounds found in plants. They are the materials that give the plant rigidity and structure. The IBS diet is a high fiber/ low fat diet. The role of fiber is crucial in controlling the quality of stool in the colon, while reducing the consumption of fat is both healthful and avoids counteracting the actions of fiber. Fiber is also called roughage or bulk.
Two types of fiber are important to human health, insoluble fiber and soluble fiber. Insoluble fiber is fiber that moves through the digestive system essentially unchanged. It is not digested, and it does not provide energy (calories). What fiber does is provide bulk to stool that helps it move through the large intestine. It also traps water, which helps the stool remain soft and easy to eliminate. In people with diarrhea, it can help trap excess water.
Studies find that the average American eats only 5-14 grams of fiber daily, but the recommended amounts are much higher. The United States Institute of Medicine (IOM) of the National Academy of Sciences has issued the following daily Recommended Dietary Intakes (RDIs) for fiber.
- men age 50 and younger: 38 grams
- women age 50 and younger: 25 grams
- men age 51 and older: 30 grams
- women age 51 and older: 21 grams
- children: 5 grams plus at least one gram for every year of age
To follow the IBS diet, individuals should gradually increase their consumption of fiber to meet or exceed the RDI. Foods that are high in insoluble fiber include:
- whole grains and foods made of whole grains, such as whole wheat bread and whole wheat pasta, couscous, or bulgur
- bran and bran breakfast cereals
- brown rice
Soluble fiber dissolves in water to form a gel-like substance. This gel helps keep stool soft. Good sources of insoluble fiber include:
- oatmeal and foods made with oats
- foods such as chili or split pea soup that contain dried beans and peas
- citrus fruits
The total amount of fiber per serving must be listed on food labels in the United States. In 2007, regulations were under consideration that that would require soluble dietary fiber to be listed separately. A good list of high-fiber foods can be found at <http://www.gicare.pated/edtgs01.htm>. Most foods that are high in fiber are naturally low in fat.
People who have trouble consuming enough fiber and are still having difficulty with IBS symptoms can ask their doctor about bulk-forming or fiber supplement laxatives. These supplements are quite safe, although they should not be used for long periods unless directed by a doctor because the colon will become dependent on them to move stool. Some common brand names of fiber-supplement laxatives are Metamucil, Citrocel, Fiberall, Konsyl, and Serutan.
These must be taken with water. They provide extra fiber that absorbs intestinal water and helps keep the stool soft. The extra bulk also helps move materials through the colon.
Low residue/low fat IBS diet
For some people, the high fiber/low fat diet controls both constipation and diarrhea. For others, the high fiber foods trigger diarrhea. These individuals may have better control of diarrhea on the low fiber/ low residue diet. This diet substitutes cooked fruits and vegetables for raw ones and reduces the amount of whole-grain products. Along with these changes, the individual chooses a variety of low-fat foods.
Some foods that help control diarrhea on the low residue IBS diet include:
- low-fat mashed potatoes
- grated apples without the skin
- cream of rice
- smooth peanut butter
Other eating tips to control diarrhea are:
- Consume food and drink at room temperature rather than at hot temperatures
- Drink liquids between meals rather than with meals
- Limit dairy products
- Rest after meals. This slows down the digestive process
Because symptoms and triggers for IBS vary greatly, these diets are starting points for individuals to develop their own list of foods that control their individual symptoms. Keeping a food journal that records what was eaten and what caused symptoms can speed the development of a personalized IBS diet.
In addition to controlling symptoms, the IBD high fiber/low fat diet has several other benefits.
- A high fiber/low fat diet has been proven in large studies to lower cholesterol levels. High cholesterol levels are directly related to heart disease
- A high fiber diet appears to help prevent type 2 diabetes
- A high fiber diet helps prevent diverticulitis. In this disease, sections of the intestine bulge out to form pockets called diverticuli that can collect food and become infected. Increased fiber helps materials
move more easily through the intestine and not become trapped in these pockets.
- The increased bulk of high-fiber foods helps people feel full faster, so they may eat less, resulting in weight loss
This diet is safe for anyone, although it may not control the symptoms of IBS for every individual. Symptoms may worsen while the individual is experimenting with personalizing the food plan.
Individuals who do not drink enough water on a high-fiber diet may develop abdominal pain and constipation.
The amount of fiber in the diet should be increased gradually. Increasing fiber too rapidly can result in abdominal pain and large amounts of gas.
This diet is accepted as healthy and often helpful in controlling the symptoms of IBS by almost all gastroenterologist. High-fiber diets are endorsed as having health benefits by the American Heart Association, the American Dietetic Association, the United States Department of Health and Human Services, and many individual healthcare organizations.
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Monique Laberge, Ph.D.