Soluble fiber is dissolved by water in the body. It's the sticky part of plants---like the sap from trees.

It has been shown that increasing fiber can lower cholesterol by 5% to 10%. To achieve this reduction people need to eat 10 grams or more of soluble fiber a day. Foods rich in this type of fiber include legumes (kidney beans, peas, lentils), whole grains (oats, barley), some fruits( citrus fruits, apples, pears and prunes), and many vegetables (broccoli, cabbage, carrots).

The mechanism by which fiber lowers cholesterol isn't known, but scientists suspect that it somehow keeps cholesterol from being absorbed by the intestine. Studies indicate that soluble fiber has a greater cholesterol-lowering effect on individuals with elevated cholesterol levels than on those with levels within the "safe" range.
                                                                                                   
There are multiple benefits in fruits and vegetables. Evidence indicates that a high-fiber diet reduces the risk of hypertension and possibly heart disease and some cancers.

Recommended Intake
The debate continues over how much soluble fiber you need to consume in order to get a significant reduction in total blood cholesterol. But the fact remains that a high-fiber diet is typically low in fat and that alone may reduce blood cholesterol. While most of the research has focused on oatmeal and oat bran, there have also been studies about other soluble fiber, such as grapefruit and apples. Instead of looking for or relying upon one "magic" food to lower cholesterol, you should get your fiber from a variety of sources.