How Soluble Fiber Lowers Cholesterol
Soluble fiber lowers cholesterol by binding to it in the small intestine. Once inside the small intestine, the fiber attaches to the cholesterol particles, preventing them from entering your bloodstream and traveling to other parts of the body. Instead, cholesterol will exit the body through the feces.Soluble fiber appears to be only effective against your LDL cholesterol, so if you also need to lower your triglycerides, or boost your HDL, soluble fiber may not be able to help you with this since the effect can range from very slight to no benefit at all. Additionally, you should not solely rely on fiber to lower your cholesterol, since the effect is only slight (LDL cholesterol can decrease by at most 18%).
The other type of fiber, insoluble fiber, is also in many healthy foods. While this type of fiber also has many healthy benefits, it does not lower cholesterol.
Sources:
Rolfes SR, Whitney E. Understanding Nutrition, 3rd ed 2005.
Third Report of the National Cholesterol Education Program
(NCEP) Expert Panel on Detection, Evaluation, and Treatment of
High Blood Cholesterol in Adults (PDF), July 2004, The National Institutes of Heath: The National Heart, Lung, and Blood Institute.

