Fiber is the nondigestible parts of edible plants, so it is a component of all fruits and vegetables. Fiber provides beneficial effects on the body, including boosting digestion, lowering cholesterol levels, reducing the risk of cardiovascular disease and diabetes and protecting the intestines from disease. The adequate intake of fiber, as recommended by the the Food and Nutrition Board of the Institute of Medicine, is 38 g per day for men under 50 years old and 25 g per day for women of this age. Men and women over 50 should get a daily 30 g and 21 g fiber, respectively.
Types of Fiber
Dietary fiber can be divided into different groups based on solubility, viscosity or fermentability. One traditional classification places fiber into the categories of soluble, which dissolves in water, and insoluble, which does not dissolve in water. Viscous fiber includes fibrous compounds that create a thick gel-like substance in water. Fermentable fiber includes any fiber that can be digested by the natural beneficial bacteria in the gut.
Fruit Fiber
Most of the fiber in fruit usually falls into the category of soluble fiber, although most fruits do contain other types in lesser amounts. The pectin in apples, oranges and berries is a fermentable fiber that is also considered insoluble. Lignin, an insoluble fiber, and gums, a viscous fiber are present in edible seeds, including strawberry seeds. A type of fiber called resistant starch can be found in bananas. The peels of apples are high in cellulose, an insoluble fiber found in cell walls.
Vegetable Fiber
Vegetables tend to be higher in insoluble fiber than soluble fiber, though they also contain a wide range of types. Cellulose can be found in root vegetables, green beans and edible vegetable skins. Inulin and oligofructose, two highly fermentable types of fiber, are found at high levels in onions and Jerusalem artichokes. Potatoes are high in lignin and carrots contain high levels of pectin.
High Fiber Fruits
One cup of pitted prunes provides 12.4 g of fiber per cup. An Asian pear is another high-fiber fruit, with 9.9 g in a single pear. A cup of raspberries provides 8 g of fiber, while a cup of blackberries has 7.6 g. A medium apple contains a total of 4.4 g of fiber and a medium pear has 5.5 g. There is 3.1 g of fiber in a medium banana and the same amount in a medium orange.
High Fiber Vegetables
Artichoke hearts have one of the highest levels of fiber, with 14.4 g per cup. One cup of cooked spinach contains 7 g of fiber and a cup of Brussels sprouts has 6.4 g. The fiber content of winter squash is also high, at 5.7 g per cup. A cup of peas provides 8.8 g of fiber and a cup of broccoli supplies 5.1 g. The fiber content of 1/4 cup of tomato paste is 2.7 g and a medium carrot has 1.7 g.
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