Dietary fiber is found exclusively in plant foods. It serves as the structural framework in plants and is one of the most abundant compounds in nature. Fiber is the part of the plant that is not broken down in the intestines by human digestive enzymes. Because it is not digested, fiber is not absorbed in the body. (Bacteria in the intestines can ferment soluble fiber, changing it to short-chain fatty acids that are absorbed, but in general, fiber itself is neither digested nor absorbed).
Fruits, vegetables, whole-grain breads and cereals, nuts, and legumes (such as dried beans, lentils, and peas) are all sources of fiber in the diet. Fiber is beneficial for a number of reasons. It helps improve intestinal health, prevents heart disease and some cancers, reduces blood pressure, regulates blood sugar, and aids in weight control.
Fiber can be either insoluble or soluble, although most fiber-containing foods have both. Insoluble fiber speeds up the movement of food through the intestines and promotes regularity. It is excreted largely intact. Insoluble fiber can be found in whole-grain foods, wheat bran, many vegetables, and fruit with skin. Soluble fiber—also called viscous fiber—dissolves when mixed with water and becomes a gel-like substance, slowing down the movement of food through the small intestine. Sources of soluble fiber include oats, peas, beans, apples, and citrus fruits; one serving of any of these foods provides about one to three grams (g) of soluble fiber.
Evidence suggests that soluble fiber is more effective at lowering cholesterol, but both types of fiber are important for your health. One of the ways soluble fiber may lower blood cholesterol is through its ability to reduce the amount of bile reabsorbed in the intestines. It works like this: When fiber interferes with absorption of bile in the intestines, the bile is excreted in the feces. To make up for this loss of bile, the liver makes more bile salts. The body uses cholesterol to make bile salts. So in order to obtain the cholesterol necessary to make more bile salts, the liver increases its production of LDL receptors.
These receptors are responsible for pulling cholesterol out of LDL molecules in the bloodstream. Therefore, the more bile salts are made from the liver, the more LDL cholesterol is pulled from the blood. It is possible that one of the short-chain fatty acids produced by the fermentation of soluble fiber in the large intestines may inhibit the amount of cholesterol produced by the liver.
Evidence suggests that more than 11 g of beta-glucan from oats can lower cholesterol up to 14.5 percent. 3 g of beta-glucan is equivalent to 70g cooked oat bran. A standard portion of cooked oat bran is about 150 g.
Did you know: according to the Food and Drug Administration (FDA), foods such as whole oats and barley that contain at least 0.75 g of beta-glucan soluble fiber per serving can state on their label that they may reduce the risk of heart disease, along with a diet low in saturated fat and cholesterol.
Get at least 5 to 10 g of fiber in per day and 10 to 25 g of soluble fiber to lower LDL cholesterol even more. Knowing how to read a label will help you to buy food that is high in fibre. The best way to increase fiber in the diet is to eat more fruits, vegetables, whole grains, and legumes.
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