Fiber is an important component of diet and is critical to maintaining health and normal body function. Unfortunately, high fiber consumption can be associated with uncomfortable digestive symptoms, including the sensation of stomach cramping. These symptoms may be particularly uncomfortable among active individuals, for whom cramping can interfere with daily activities and workouts.
Significance
Fiber is a carbohydrate---it's chemically related to sugars and starches, but is indigestible and therefore provides no calories. According to the Mayo Clinic, fiber serves many important roles in the body, despite its lack of caloric content. "Dietary fiber," notes the Mayo Clinic, "...is probably best known for its ability to prevent or relieve constipation. But fiber can provide other health benefits as well, such as lowering your risk of diabetes and heart disease." They recommend that women consume 25g per day, and that men aim for 38g per day of fiber.
Metabolism
According to biochemists David Nelson and Michael Cox, fiber is composed of the same basic sugar (glucose) units that are linked together to form starch, but humans lack the necessary digestive enzyme---cellulase---to break the units apart. Bacteria in the intestine, however, do produce cellulase and are able to metabolize the glucose contained in fiber. As bacteria break down cellulose for energy, they produce a large quantity of gas in the human digestive tract.
Symptoms
You're most likely to experience discomfort upon eating fiber if you consume more than you're used to, notes Mother Nature, an Internet health and wellness advisory site. Although increasing fiber intake may relieve either constipation or diarrhea, Mother Nature advises, "eating too much fiber without giving your body time to adjust ... may actually cause more gas and diarrhea." Runner's World magazine, too, suggests that reducing dietary fiber can help relieve cramping and discomfort during runs.
Sources
High-fiber foods include grains (particularly whole grains), fruits, vegetables, beans and other legumes, and nuts or seeds, according to the Mayo Clinic. For runners (and others) experiencing fiber-related digestive cramping, Runner's World magazine suggests replacing "high-fiber fruits and veggies like pears and green peas with lower-fiber cantaloupe and tomatoes." Other fruits and vegetables with less fiber, less than 1 g per serving, include zucchini, olives, grapes, and grapefruit.
Expert Insight
The Mayo Clinic provides the reminder that although high-fiber foods may cause stomach cramping, they are important to health and should not be avoided entirely, except in cases of certain diseases. "Increase fiber in your diet gradually over a period of a few weeks. This allows the natural bacteria in your digestive system to adjust to the change," the website notes. Consuming large amounts of water helps the body adjust to increased fiber and helps the fiber function properly. "Fiber works best when it absorbs water, making your stool soft and bulky," the site indicates.
References
- Mayo Clinic: Fiber
- "Principles of Biochemistry"; David L. Nelson, Ph.D., Michael M. Cox, Ph.D.; 2008
- Mother Nature: Fiber and Cramping
- Runner's World: Fiber and Cramping
