Fiber is also known as roughage or indigestible plant matter.
In the body, fiber slows digestion, stabilizes blood sugar levels and aids waste elimination.
The RDA for fiber is 38 grams and 25 grams for men and women, respectively, but goes down to 30 and 21 grams after age 50.
Fiber has always been a major component of natural diets, where it is present in numerous fruits and vegetables. In the last half of the 20th century, researchers determined that fiber consumption is linked to lower risks of heart disease and cancer.
Today, many food companies add fiber to their products.
A deficiency of fiber is generally caused by a diet focused on refined foods. In efforts to make fast food and packaged snacks more palatable, food manufacturers have commonly refined their ingredients so that little or no fiber is in the final products.
White flour, refined sugar and fiber-free fruit juices are examples of these items.
Whole-food diets can also result in low fiber levels if they do not include enough fruits and vegetables rich in roughage.
Whereas some whole foods, such as potatoes, are fairly low in fiber, others, such as kale, are very high in the substance.
Some conditions can result in buildup of fiber in the body.
Gastroparesis, the clinical term for delayed stomach emptying, can cause masses of fiber called bezoars to build up in the stomach and create dangerous blockages.
Another way in which fiber can become excessive in the body is through low levels of the gut bacteria that break down fiber. After antibiotic use or heavy consumption of chlorinated water, levels of such beneficial bacteria can be very low or absent.
Finally, a very high-fiber diet that includes large amounts of fibrous fruits and vegetables can result in accumulation of fiber in the intestines of some individuals.