Daily Recommended Fiber Intake
Women
25 grams per day, for women younger than 50
21 grams per day, for women older than 50
Men
38 grams per day, for men younger than 50
30 grams per day, for men older than 50
Most nutritionists and diet experts suggest that approximately 20-30 percent of our daily fiber intake should come from soluble fiber.
There are two basic types of dietary fiber: soluble and insoluble fiber, depending on whether it dissolves in water. Both soluble and insoluble fiber is indigestible by humans. Although insoluble fiber and its health benefits have been known for some time, the benefits of soluble fiber have only recently appeared.
Types of Insoluble Fiber
Insoluble dietary fiber is a natural laxative and includes cellulose and lignin which occur in whole grains (especially wheat bran), and hemicellulose (partly soluble) found in whole grains, nuts, seeds, fruits and vegetables.
Types of Soluble Fiber
Water soluble dietary fiber binds with and removes certain things in the gut. Types of soluble fiber include pectin, which occurs in fruits (apples, strawberries, citrus fruits); beta-glucans, found in oats, barley and rye; gums, found in beans, cereals (barley, oats, rice), seeds and seaweed; and arabinose, found in legumes/pulses. Soluble fiber can be further classified into fermentable and non-fermentable types. Fermentable soluble fiber helps to feed our intestinal bacteria - the "healthy" bacteria that helps us digest and absorb nutrition from our food.
Fiber-Rich Foods Contain Both Types of Fiber
Many fiber-rich foods, especially plant-foods, contain both soluble and insoluble fiber in varying proportions. But one type of fiber usually dominates.
Digesting Dietary Fiber
Although fiber is mainly indigestible, the human digestive system does react with it. Bacteria in the digestive tract attack it, causing methane gas to be released in the process, which can cause bloating and flatulence. In addition, fiber - if eaten in excessive quantities - may interfere with the uptake of minerals and vitamins. Finally, excessive soluble fiber may attract too much water from the cells, thus impeding cell-function. For these reasons, it is best to increase your fiber intake gradually and avoid fiber supplements except in carefully measured doses.
Benefits of Soluble Fiber
The health benefits of water soluble fiber occur largely in the early part of the digestive system (stomach and small intestine) and include the following:
* Soluble fiber slows down digestion in the stomach and small intestine. This helps to slow down the conversion of other carbohydrates into glucose, thus stabilizing blood glucose levels. The presence of fiber in carb-rich foods actually lowers the glycemic index of that food. By slowing down the digestive process in the stomach thus forcing nutrients to spend more time in the digestive zone, soluble fiber may also increase the uptake of minerals and other nutrients in food.
* Soluble fiber forms a thick gel when it comes into contact with water in the digestive tract. This swelling-effect, allied to the slowing down of the digestive process, increases our feeling of fullness (satiety) without adding calories. Fiber is therefore a useful element in any healthy weight loss diet.
* Soluble fiber appears to reduce blood cholesterol levels. This is because the fiber binds with bile acids and cholesterol in the digestive tract, preventing them from being absorbed by the body.
* Soluble fiber may also have cancer benefits. Modified citrus pectin, when fed to rats, appeared to reduce the size of tumors. In some as yet unknown way, the pectin appears to interfere with cancer cells linking together to form tumors.
Benefits of Insoluble Fiber
The health benefits of insoluble dietary fiber occur largely in the later part of the digestive system (colon) and include the following:
* Insoluble fiber improves the health of the intestinal tract by increasing stool volume and stimulating normal bowel contractions (peristalsis) thus reducing transit time through the colon. This protects against digestive complaints like constipation, irritable bowel syndrome (IBS) and diverticulitis.
* By accelerating the speed of food through the intestinal tract, insoluble fiber may help prevent digestive disorders such as constipation or diverticulosis (infection caused by food getting stuck in small pouches in the wall of your colon. It may also reduce the absorption of salt (thus reducing the risk of raised blood pressure) and toxins.
Good Sources of Dietary Fiber
Haricot Beans Parsnips
Spinach Kidney Beans
Soy Beans All Bran
Apple Shredded Wheat
Apricots, dried Bread, High-Bran
Blackcurrants Bread, wholemeal
Figs Oatmeal
Mango Oatbran
Orange Broccoli
Pear Pasta, wholewheat
Prunes Brussels Sprouts
Almonds, oil-roasted Peas, frozen
Peanuts, dry roasted Parsnips
Spinach