Some foods with high amounts of water-soluble fiber include vegetables; the legume family, which includes peas, lentils, peanuts and beans; and fruits, though some fruits have more soluble fiber than others. Grains are another good source of soluble fiber. Nuts and non-legume seeds are not good sources of soluble fiber, with the exception of flaxseeds, which can be added in small amounts to breakfast cereals or other foods.
Some vegetables with high amounts of fiber include Brussels sprouts, sweet potatoes, turnips and asparagus. Brussels sprouts have the most fiber among these vegetables at 2 grams per 1/2-cup portion. The others have 1.7 grams or more in 1/2 cup.
Seeds that have a pod or shell are called legumes. Legumes that have a very high soluble fiber content include navy beans, kidney beans and black beans, all of which have at least 2 grams in 1/2 cup.
Some fruits with particularly high amounts of soluble fiber include oranges, grapefruits, mangoes and apricots. A small orange contains about 1.8 grams of soluble fiber in addition to 1.1 grams of insoluble fiber.
Whole grains retain the bran, endosperm and germ that contain the soluble fiber. When food processors remove these parts of the grain, they also remove some of the fiber and other nutrients. Oatmeal and oat bran are two grains that hold a lot of fiber. Oatmeal has about 1.4 grams of soluble fiber in a 1/3-cup portion. Oat bran contains about 2.2 grams per 3/4 cup. Barley holds 1 gram of soluble fiber per 1/2 cup.