What is Dietary Fiber
Dietary fiber is the indigestible portion of plant foods which are subdivided into 2 components:
- Soluble: fiber that is readily fermented in the colon into gases and physiologically active byproducts. This type of fiber dissolves in water to form a gel-like material. It can help lower blood cholesterol and glucose levels.
- Insoluble: fiber inert and provide bulking or metabolically fermented in the large intestine as a prebiotic fiber. This type of fiber promotes the movement of material through your digestive system and increases stool bulk, so it can be of benefit to those who struggle with constipation or irregular stools.
Fiber has been causing controversy since early 1950's, because food scientists, nutritionists, and medical experts about the exact definition of dietary fiber.
Benefits and Functions of Dietary Fiber
Dietary fibers are important for many functions in the body. They help in reducing cholesterol levels, making sure the blood sugar levels are normal, they help in bowel movement and make sure they are regular. They can also treat heart attacks and high blood pressure (cardiovascular diseases), obesity and diabetes (metabolic disorders), intestinal problems (constipation, diverticulosis, diverticulitis, gallstones, appendicitis, hemorrhoids, polyps, and colon cancer), varicose veins and blood clots (deep vein thrombosis).
Food Sources of Dietary Fiber
Soluble fiber is found in the following food items:
- legumes (peas, soybeans, lupins and other beans)
- oats, rye, chia, and barley
- some fruits and fruit juices (including prune juice, plums, berries, bananas, and the insides of apples and pears)
- certain vegetables such as broccoli, carrots, and Jerusalem artichokes
- root tubers and root vegetables such as sweet potatoes and onions (skins of these are sources of insoluble fiber also)
- psyllium seed husk (a mucilage soluble fiber) and flax seeds
- nuts, with almonds being the highest in dietary fiber
Insoluble fiber is found in the following food items:
- whole grain foods
- wheat and corn bran
- legumes such as beans and peas
- nuts and seeds
- potato skins
- vegetables such as green beans, cauliflower, zucchini (courgette), celery, and nopal
- some fruits including avocado, and unripe bananas
- he skins of some fruits, including kiwifruit and tomatoes
A deficiency of fiber shall not cause any serious effects on the body. It would develop problems like constipation, hemorrhoids, colon cancer: disease, obesity and high cholesterol levels.
An excess of fiber can, on the other hand, cause a water imbalance situation in our body, which can eventually lead to dehydration. People who decide to suddenly increase their fiber intake are often advised to double or triple their water intake for this reason.
In addition, excessive intake of nonfermentable fiber, typically in the form of supplements, may lead to mineral deficiencies by reducing the absorption or increasing the excretion of minerals, especially when mineral intake is too low or when mineral needs are increased such as during pregnancy, lactation, or adolescence.