Fiber is a plant-based substance needed for peak digestive function, but you do not actually digest it. Fiber's advantages lie in its ability to pass through your body virtually unchanged, although soluble fiber does change in consistency. You need a minimum fiber intake each day, depending on your age and sex, to keep your bowels moving smoothly.
Digestibility
Your body breaks down most foods as they pass through your digestive system, absorbs the nutrients and transforms the remaining part into stools, which are eliminated. Your stomach and intestinal enzymes have no effect on fiber, although some dietary roughage is metabolized by bacteria in the gut. Most fiber keeps its original shape as it passes through your body if it is the insoluble type. Soluble fiber absorbs water, which transforms it into a jelly. The gel still does not get digested.
Purpose
Fiber's unchanging nature in your intestines helps create healthy stool. Fiber adds moisture and volume, which facilitates easy bowel movements. Small, hard chunks of feces are difficult to pass, forcing you to strain and potentially causing constipation, hemorrhoids and other issues. Soluble fiber's ability to absorb water helps firm up loose stools, reducing diarrhea, according to the Mayo Clinic website. Dietary roughage also eases irritable bowel symptoms and prevents a condition called diverticulosis that can otherwise lead to a digestive disease called diverticulitis.
Sources
Plants are the only fiber source, as dietary roughage is completely absent in meat. Many vegetables and fruits are fiber-rich, as are whole-grain products like pasta and bread. Nuts, oats and legumes are also good fiber sources. Many stores sell fiber supplements to beef up the amount of bulk you get each day if you cannot meet the recommended amount through diet alone. The fiber in supplements works in the same manner as roughage in food, as it is mainly soluble fiber derived from a plant called psyllium. Like other soluble forms, it resists digestion and becomes a gel as it absorbs liquid.
Amount
Daily fiber requirements vary, based on your gender and age. Men should consume at least 38 g of fiber every day until they reach age 50. After that point, they require a minimum of 30 g, according to the American Academy of Family Physicians. Women need at least 25 g of daily fiber up to age 50, after which the minimum requirement drops to 21 g. Exceeding the recommended amount is not harmful, but do not suddenly increase your fiber intake, or you may get symptoms like stomach pain and excess gas. A gradual increase prevents unwanted side effects.
References
- Colorado State University Extension; Dietary Fiber; J. Anderson et. al.; December 2010
- MayoClinic.com; Dietary Fiber, Essential for a Healthy Diet; November 2009
- National Digestive Diseases Information Clearinghouse; Diverticulosis and Diverticulitis; July 2008
- MedlinePlus; Blond Psyllium; July 2011
- FamilyDoctor.org; Fiber, How to Increase the Amount in Your Diet; December 2010
- University of Maryland Medical Center; Fiber; February 2010
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