Insoluble fibers are those which do not dissolve in water, do not form gels (are not viscous), and are less readily fermented. Insoluble fibers, such as cellulose, form structures such as the outer layers of whole grains (bran), the strings of celery, the hulls of seeds, and the skins of corn kernels. These fibers retain their shape and rough texture even after hours of cooking. In the body, they aid digestive system by easing elimination.
Insoluble fibers are generally found in whole grains, such as wheat, rye, and brown rice, and are found in many vegetables. These fibers are not associated with reducing cholesterol levels but are known for promoting regular bowel movements, alleviating constipation, and reducing the risk for diverticulosis. Examples of insoluble fibers include the following: Lignins are non-carbohydrate forms of fiber. Lignins are found in the woody parts of plant cell walls and in carrots and the seeds of fruits and berries. Lignins are also found in brans (the outer husk of grains such as wheat, oats, and rye) and other whole grains. Cellulose is the main structural component of plant cell walls. Cellulose is a chain of glucose units similar to amylose but, unlike amylose, cellulose contains bonds that are non-digestible by humans. Cellulose is found in whole grains, fruits, vegetables, and legumes. It can also be extracted from wood pulp or cotton, and it is added to foods as an agent for anticaking, thickening, and texturizing of foods. Hemicelluloses contain glucose, mannose, galacturonic acid, and other monosaccharides. Hemicelluloses are found in plant cell walls and they surround cellulose. They are the primary component of cereal fibers and are found in whole grains and vegetables. Although many hemicelluloses are insoluble, some are also classified as soluble.
Food Sources of Insoluble fiber
|Food name||Weight||Insoluble fiber (g)|
|Almond butter||1 tbsp||0.50|
|Almond paste||1 tbsp||0.70|
|Apple juice||1 cup||0.20|
|Sweetened apple||1 medium||3.60|
|Unsweetened apple||1 medium||4|
|Dried apple||1 cup||3.40|
|Apple with skin||1 medium||2.70|
|Apple without skin||1 medium||1.70|
Health Benefits of Insoluble fiber
Here we will come to known the benefits provided by Insoluble fiber:
- Gastrointestinal health
Dietary fibers also enhance the health of the large intestine. The healthier the intestinal walls, the better they can block absorption of unwanted constituents. Taken with ample fluids, insoluble fibers such as cellulose (as in cereal brans, fruits, and vegetables) increase stool weight, ease passage, and reduce transit time.
Large, soft stools ease elimination for the rectal muscles and reduce pressure in the lower bowel, preventing constipation and making it less likely that rectal veins will swell (hemorrhoids). Fiber prevents compaction of the intestinal contents, which could obstruct the appendix and permit bacteria to invade and infect it (appendicitis). In addition, fiber stimulates the GI tract muscles so that they retain their strength and resist bulging out into pouches known as diverticula. Recommendations typically suggest increasing fiber to protect against diverticular disease, although research findings are inconsistent.
- Digestive disorders
Because insoluble fiber increases feces weight and bulk, it promotes normal bowel movements in adults and children. In general, the greater the weight of the feces is, the more quickly it passes through the large intestine. Insoluble fiber is therefore helpful in preventing constipation (infrequent passage of feces). Fiber also helps reduce the risk of diverticulosis, a condition in which small pouches form in the colon wall, usually from the pressure created within the colon by the small bulk and/or from straining during bowel movements. A diet high in insoluble fiber is also used to prevent or treat hemorrhoids, enlarged veins in the lower rectum. Larger, soft feces are easier to eliminate, and so there is less pressure and the rectal veins are less likely to swell.
- Colon cancer
Studies have generally noted an association between low total fat intake, high fiber intake, and a reduced incidence of colon cancer. The exact mechanism for reducing the risk is not known, but one possibility is that insoluble fiber adds bulk to stool, which in turn dilutes carcinogens (cancer-causing substances) and speeds their transit through the intestines and out of the body. More research needs to be done before we know for certain that fiber decreases the risk of colon cancer, but until then, health-care professionals strongly suggest eating plenty of fruits, vegetables, beans and peas, and whole grains.
- Cure for constipation
You already read about the benefits of insoluble fiber—the kind in wheat bran. It holds on to water, helping to soften and add bulk to waste in the intestines. This action helps stools pass through the digestive system more quickly with normal frequency and ease. As a result, fiber helps prevent constipation and the discomfort that goes with it. When soft stools easily pass out of the body, there’s no need for strained bowel movements. As a result, hemorrhoids—a painful swelling of the vein near the anus—are less likely to form. Softer, bulkier stools put less pressure on the colon walls and so reduce the chance of hemorrhoids, too. With diverticulosis, tiny sacs form when the intestinal wall, especially in the colon, gets weak. These sacs may become infected and quite painful, a problem called diverticulitis.
- Bowel health
Fiber supplies mass to the feces, making elimination much easier. This is especially true for insoluble fibers. When enough fiber is consumed, the stool is large and soft because many types of plant fibers attract water. The larger size stimulates the intestinal muscles to contract, which aids elimination. Consequently, less pressure is necessary to expel the stool.
When too little fiber is eaten, the opposite can occur: very little water is present in the feces, making it small and hard. Constipation may result, which forces one to exert excessive pressure in the large intestine during defecation. This high pressure can force parts of the large intestine (colon) wall out from between the surrounding bands of muscle, forming many small pouches called diverticula. Hemorrhoids may also result from excessive straining during defecation.
Diverticula are asymptomatic in about 80% of affected people; that is, they are not noticeable. The asymptomatic form of this disease is called diverticulosis . If the diverticula become filled with food particles, such as hulls and seeds, they may eventually become inflamed and painful, a condition known as diverticulitis . Surprisingly, intake of fiber then should be reduced to limit further bacterial activity. Once the inflammation subsides, a high-fiber diet is resumed to ease stool elimination and reduce the risk of a future attack.
Over the past 30 years, many population studies have shown a link between increased fiber intake and a decrease in colon cancer development. Most of the research on diet and colon cancer is focusing on the potential preventive effects of fruits, vegetables, whole-grain breads and cereals, and beans (rather than just fiber). Smoking, obesity in men, excessive alcohol use, starch- and sugar-rich foods, and processed meat intake are under study as potential causes of colon cancer. Overall, the health benefits to the colon that stem from a high-fiber diet are partially due to the nutrients that are commonly present in most high-fiber foods, such as vitamins, minerals, phytochemicals, and in some cases essential fatty acids. Thus it is more advisable to increase fiber intake using fiber-rich foods, rather than mostly relying on fiber supplements.
- Treat diverticulitis
It is a health condition indicating by inflammation or infection of pouches in intestinal walls. It is a prevalent age related disorder occurring in one third of those over 45 years or two third of people over age 85. Its development is related with diet low in fiber. Literally, this condition is common in vegetarians as they consume more fiber in comparison to non-vegetarians. The consumption of adequate fiber lowers the chances of diverticular disease by 40 percent.