What is dietary fiber? The dietary fiber or “fiber” includes edible plant parts that cannot be digested or absorbed in the small intestine and pass to the intestine intact thick. It includes non-starch polysaccharides (e.g. cellulose, hemicellulose, pectins, and gums), oligosaccharides (e.g. inulin), lignin and associated plant substances (e.g. waxes and suberin). Dietary fiber also includes a type of starch known as resistant starch (found in seeds and partially milled grains and some breakfast cereals), it is called so as it resists digestion in the small intestine and reaches the large intestine without changes.
The dietary fiber is found in fruits (pears, strawberries, blackberries, raspberries, currants, and oranges), vegetables (Brussels sprouts, artichokes, onions, garlic, corn, peas, green beans, and broccoli), legumes (lentils, chickpeas, Beans) and whole grains (all bran and oat bran cereals, whole grain breads and mixed grains).
The dietary fiber is cataloged many times according to its solubility in soluble or insoluble. Both types of fiber are found in different proportions in foods containing fiber. Good sources of soluble fiber are oats, barley, fruits, vegetables and legumes (beans, lentils, chickpeas). Whole grains and whole wheat bread are sources rich in insoluble fiber.
Ingested dietary fiber moves along the large intestine where it is partially or completely fermented by intestinal bacteria. During the fermentation process, by-products such as short-chain fatty acids and gases are formed. It is the combined action of the fermentation process and the formed byproducts that contribute to the beneficial effects of dietary fiber on health.
The main physiological effects attributed to the use of dietary fiber:
Dietary fiber, particularly soluble fiber, helps prevent constipation by increasing stool weight and decreasing intestinal transit time. This effect is enhanced if fiber intake is accompanied by an increase in water intake.
Short chain fatty acids, produced when fiber is fermented by gut bacteria, are an important source of energy for colon cells and can inhibit the growth and proliferation of intestinal tumor cells.
By improving bowel function, dietary fiber can reduce the risk of diseases and disorders such as diverticular disease or hemorrhoids, and may also have a protective effect on colon cancer.
Blood glucose levels
Soluble fiber can slow the digestion and absorption of carbohydrates and therefore reduce the increase of blood glucose after a meal (postprandial) and insulin response. This can help people with diabetes better control their blood glucose levels.
Cholesterol in the blood
The results of epidemiological studies have identified another role of dietary fiber in the prevention of coronary heart disease (CHD). Clinical trials confirm the results of these epidemiological studies. Isolated viscous fibers such as pectin, rice bran or oat bran can reduce both total serum cholesterol and low-density lipoprotein (LDL or bad) levels. At the same time, research continues to show that diets high in a dietary fiber blend also protect against other heart disease.
While preventing constipation, improving blood glucose levels, and blood lipid profiles predominate as beneficial results of a diet high in dietary fiber, other benefits are worthy of mention. For example, fiber increases the volume of the diet, without adding calories, can have a satiating effect on the appetite and aid in weight control.
To have all the benefits of fiber it is important to vary the sources of fiber in the diet. Diets with fruits, vegetables, beans and lentils / whole grains not only provide dietary fiber, but also many other nutrients and food components essential for good health.