Dietary fiber is the indigestible part of food that passes through the large bowel. Fiber is classified as either soluble or insoluble.
Insoluble fiber is associated with the time it takes food to travel through the intestines. Because of its ability to bind with water, insoluble fiber improves bowel movements. In natural sources, it’s found mostly in wheat. Other sources include skins of fruits and vegetables.
Soluble fiber, found in oat bran, beans, vegetables, and fruit, has been associated with lowering cholesterol.
Consuming adequate amounts of fiber is important, because too little fiber can lead to constipation and the formation of hemorrhoids. High fiber does not cause a laxative effect; it’s only effect on the stool is to increase the bulk, not frequency. Too little fiber intake can also lead to diverticulitis, a painful condition in which small pouches on the bowel become irritated and inflamed. A general recommendation for daily fiber intake is 25mg.
Fiber does help in weight loss but the effect is minimal. In a number of studies, the average weight loss is about one-third of a pound per week. That may not like much but ANY weight loss helps and this is a relatively painless one. Natural foods with a high fiber content have been shown to promote greater satiety (a feeling of fullness) than more processed and/or refined foods [1][2][3]. One possible reason is that with natural foods that undergo less processing and refining a greater amount of calories and fiber reach the latter part of the small. Research has shown that exposing the latter part of the small intestine to small quantities of food results in a marked suppression of hunger and unnecessary food intake [4]. There is reason to believe that more undigested food and fiber reaching the latter part of the small intestine may enhance satiety because intestinal bypass surgery (which also results in more undigested calories reaching the ileum) generally suppresses appetite and promotes weight loss [5].
Fiber also helps to prevent constipation (one of the most common side effects of dieting), stomach cancer, and high cholesterol. Many physicians are now recommending it be taken daily. I find that most people prefer Citrucil or sugar-free Metamucil. It works every bit as well, or better than the much more expensive chitin or fiber-in-a-pill (Fiber Con or FiberAll, e.g.).
Chitin is a form of fiber, often derived from the shell of sea animals such as crabs and snails. It’s often reported to have wonderful properties with exaggerated claims that it cures every ailment known to man.
Flaxseed, taken daily in two rounded tablespoon doses, may help give protection against hormonally related cancers. Flaxseeds are rich sources of lignans and omega-3 fatty acids. The plant lignans in flaxseed help to block excessive estrogen activity. Flaxseeds should either be soaked overnight or freshly ground right before ingesting. They can then be added to cereal or yogurt.
1.[Slabber M et al Am J Clin Nutr 1994;60:48-53]
2.[Haber GB et al Lancet 1977;2:679-82]
3.[Bjorck I et al Am J Clin Nutr 1994;59(suppl):699s-705s]
4.[Welch IM et al Gut 1988;29:306-11]
5.[Pi Sunyer F. Am J Clin Nutr 1976;29:409-16]