Dietary fibre
Dietary fiber, dietary fibre, or sometimes roughage or ruffage is the indigestible portion of plant foods having two main components:
Soluble fiber dissolves in water to form a gel-like substance. Sources of soluble fiber are oats, legumes (beans, peas, and soybeans), apples, bananas, berries, barely, some vegetables, and psylluim.
Insoluble fiber increases the movement of material through your digestive tract and increases your stool bulk. Sources of insoluble fiber are whole wheat foods, bran, nuts, seeds, and the skin of some fruits and vegetables.
Dietary fiber includespolysaccharides, oligosaccharides, lignin, and associated plant substances. They promote beneficial physiological effects including laxation, and / or blood cholesterol attenuation, and/or blood glucose attenuation.”
Dietary fiber consists of nondigestible carbohydrates and lignin that are intrinsic and intact in plants. This includes plant nonstarch polysaccharides (for example, cellulose, pectin, gums, hemicellulose, and fibers contained in oat and wheat bran), oligosaccharides, lignin, and some resistant starch.
Functional fiber consists of isolated, nondigestible carbohydrates that have beneficial physiological effects in humans. This includes nondigestible plant (for example, resistant starch, pectin, and gums), chitin, chitosan, or commercially produced (for example, resistant starch, polydextrose, inulin, and indigestible dextrins) carbohydrates.
Total fiber is the sum of dietary fiber and functional fiber.
Role of dietary fiber in health and disease
Dietary fiber has been, for several years, the glamour ingredient in popular nutrition. Based on epidemiological evidence, lack of fiber in the diet has been impugned as a major risk factor for development of colon cancer, heart disease, diabetes and a variety of lesser ills.
Some components of the complex mixture of substances called fiber will reduce cholesterol levels to a modest extent and will inhibit atherosclerosis induced by diet.
Studies associated a low intake of dietary fiber with the incidence of colon cancer, heart disease, diabetes, and other diseases and disorders. Dietary fiber is not a single substance. There are significant differences in the physiological effects of the various components of dietary fiber. A Recommended Dietary Allowance for dietary fiber has not been established. However, an adequate amount of dietary fiber can be obtained by choosingseveral servings daily from a variety of fiber-rich foods such as whole-grain breads and cereals, fruits, vegetables, legumes, and nuts.
High-fiber diets may be useful for people who wish to lose weight. Fiber itself has no calories, yet provides a "full" feeling because of its water-absorbing ability. For example, an apple that contains fiber is more filling than a half cup of apple juice that contains about the same calories but no fiber. Foods high in fiber often require more chewing, thus it takes more time to eat, so a person is unable to eat a large number of calories in a short amount of time.
Working
Besides trapping fat and cholesterol that would otherwise be digested by the body, there are two proposed mechanisms for the lowering of blood cholesterol by soluble fiber. In the first scenario, soluble fiber traps bile acids in the same way that it traps sugars and carries them out of the body as waste. Bile acids are produced from cholesterol in the liver. Therefore, if bile acids are removed, the body pulls cholesterol from the bloodstream to produce more.
In the second theory, soluble fiber shifts the bile acid pools away from cholic acid and toward another acid (chenodeoxycholic acid) that inhibits an enzyme involved in fat and cholesterol production (3-hydroxy 3 methylglutaryl CoA reductase). Decreased enzyme activity means less cholesterol produced by the liver and lower blood cholesterol levels.
Fiber for controlling diabetes
A high-fiber diet may be just what the doctor ordered to get your blood sugars under control. Keeping our blood sugars stable is a goal that we would all benefit from. If you don't have type 2 diabetes, this could be the way to prevent it. If you do have it, this could be the way to keep it under control. The best time to address type 2 diabetes is before it has developed. Research has shown that high-fiber diets can help prevent this form of diabetes. The most recent study on done on overweight and obese men and women without diabetes showed reductions in blood sugar and insulin with the use of a high soluble fiber supplement. A German clinical trial reported that eating fiber-enriched bread for only three days improved insulin sensitivity in overweight and obese women by 8%. If a diet intervention this small can have that great of an impact, you can imagine what years of following a high-fiber diet, filled with vegetables, fruits and whole grains would do. The good news for those with diabetes is that increasing your fiber now can also prevent long-term complications from diabetes. Soluble fiber has been found to produce significant reductions in blood sugar in 33 of 50 studies testing it. In clinical intervention trials ranging from two to 17 weeks, consumption of fiber was shown to decrease insulin requirements in people with type 2 diabetes. If you have ever had to inject yourself with insulin, you can appreciate how much easier and less painful it would be to increase your fiber intake to avoid the need for insulin injections.
Fiber for preventing heart disease
If we were to sit down and have a "heart to heart," I would tell you that one of the best things that you could do on your own to protect your heart is to follow a high-fiber diet. Numerous studies have produced compelling evidence to support this. In a Harvard study of over 40,000 male health professionals, researchers found that a high total dietary fiber intake was linked to a 40% lower risk of coronary heart disease, compared to a low-fiber intake. Another study of over 31,000 California Seventh-day Adventists found a 44% reduced risk of nonfatal coronary heart disease and an 11% reduced risk of fatal coronary heart disease for those who ate whole wheat bread compared with those who ate white bread. One minor change in their diets provided a protective effect that could save their lives.
Another strong predictor of heart disease is abnormal blood cholesterol, LDL, and/or HDL levels. It appears that soluble fiber reduces the absorption of cholesterol in your intestines by binding with bile (which contains cholesterol) and dietary cholesterol so that the body excretes it. The oat bran and bean fiber intervention trials where dietary fiber supplementation was combined with a low-fat diet shows that reductions in total cholesterol levels ranged from 8-26%. Other studies have shown that 5 to 10 grams of soluble fiber a day decreases LDL cholesterol by about 5%. All of these benefits will occur regardless of changes in dietary fat. In a trial with low fat and low fat plus high fiber groups, the group consuming high fiber exhibited a greater average reduction (13%) in total cholesterol concentration than the low fat (9%) and the usual diet (7%) groups. It seems that you don't have to change everything to gain something.