Types Of Dietary Fiber: Soluble & Insoluble
Dietary fiber comprises a group of low-GI (glycemic impact) carbohydrates whose chemical structure prevents them from being digested. We lack the digestive enzymes needed to do so. Thus, fiber can’t be metabolized to glucose. Not all fibers are created equally, but research shows each is as equally important as the next. Sources of dietary fiber are usually divided according to whether they are water-soluble or not.
Both types of fiber are present in all plant foods, with varying degrees of each according to a plant’s characteristics.
Insoluble fiber possesses the passive water-attracting properties that are needed help to increase bulk, soften stool and shorten the transit time through the intestinal tract. Generally thought of as “roughage”, insoluble fiber moves quickly through the digestive system.
As such, this fiber (typically found in whole grain products), is helpful in the treatment and prevention of constipation, hemorrhoids and diverticulosis (pouches of the intestinal wall that can become inflamed and painful).
Sources of insoluble fiber include seeds, whole wheat, wheat, corn bran, flax seed and vegetables such as celery, green beans and potato skins. It is also found in popcorn.
While insoluble fiber doesn’t seem to help lower blood cholesterol, it an important aid in normal bowel function.
Meanwhile soluble fiber acts in a different, yet equally important way. It undergoes metabolic processing through fermentation, yielding end-products with significant health effects.
Plums, for example, have a thick skin covering a juicy pulp. The plum’s skin is an example of an insoluble fiber source, whereas soluble fiber sources are inside the pulp.
During digestion, soluble fiber forms a gel-like substance, which helps the body handle fats, cholesterol and carbohydrates. Soluble fiber also plays a significant role in helping to lower blood cholesterol levels, one of the main risk factors for the development of cardiovascular disease, according to the US Dry Bean Council.
In general, soluble fiber is found in oatmeal, barley and rye, beans, peas and lentils, fresh and dried fruits, and most vegetables.
Fruits, vegetables, some whole-grain foods, beans and legumes are all good quality fiber-rich foods. The American Heart Association Eating Plan suggests that you eat both foods to maintain a healthy diet and to consume the recommended daily intake of 25 to 30 grams daily.