Soluble fiber is an indigestible form of carbohydrate found in a variety of plant foods, such as oats, legumes, fruits and vegetables. This type of fiber helps remove artery-clogging LDL cholesterol from the body, which ultimately lowers blood levels of total and LDL cholesterol. Maintaining low blood cholesterol levels, especially low LDL cholesterol, is one way to lower your risk of developing heart disease.
Function
Your liver produces bile acids and sends them to the intestine to assist in digesting fats and fatty substances. Normally, bile acids help with the absorption of cholesterol through your intestinal wall and into your bloodstream. When soluble fiber is also present in your gastrointestinal tract, it soaks up water from the intestine and forms a gel that traps some of these bile acids and interrupts the process of absorption. Instead of being absorbed into your body, some of these trapped bile acids are excreted in waste matter. When bile acids are excreted, cholesterol particles go with them. Over time, this process helps lower blood cholesterol levels and reduce your risk of heart disease.
Sources
There are two types of fiber, soluble and insoluble, and most plant foods contain some of each. The best sources of soluble fiber to include in your diet are oats and oat products, such as oat bran and instant, old-fashioned and steel-cut oatmeal; fruits, such as apples, pears, oranges, grapefruits, strawberries, blueberries, apricots and prunes; vegetables, such as cabbage, carrots, Brussels sprouts and sweet potatoes; and legumes, including black beans, kidney beans, pinto beans, Lima beans, garbanzo beans, black-eyed peas, lentils and split peas. Soluble fiber is also found in psyllium seed husks, which are processed and sold as a supplemental powder or pill in health foods stores, drugstores, grocery stores and elsewhere.
Amounts
To lower your cholesterol and help prevent heart disease, the National Cholesterol Education Program recommends consuming 10g to 25g of soluble fiber each day. One-half cup cooked black beans, kidney beans or navy beans provide approximately 2g soluble fiber. Lima beans, pinto beans and garbanzo beans, or chick peas, provide about 1 g. A three-quarter-cup serving of cooked oat bran supplies about 2g of soluble fiber while a third-cup dry oatmeal supplies about 1.5g. One-half cup of cooked sweet potatoes, turnips or Brussels sprouts contains about 2g. Other cooked vegetables that supply about 1g of soluble fiber in a half-cup serving include broccoli, carrots, okra and green peas. Fruits that provide 1g or more soluble fiber per average serving include apples, dried apricots, dried figs, grapefruit, mango, oranges, peaches, pears, plums and strawberries. Rye and pumpernickel breads supply an estimated 1g soluble fiber per slice.
Effects
Sometimes, foods that provide soluble fiber in the diet can cause unwanted side effects, such as abdominal discomfort and intestinal gas, especially if you eat too much at one time. This is particularly true if you suddenly add significantly more fiber to your diet than you normally had eaten. To avoid problems, increase the fiber in your diet gradually, building up to the recommended amounts of at least 25g total fiber with at least 10g coming from soluble fiber. Drink plenty of water throughout the day as you increase the amount of fiber you eat.
Considerations
Adding more soluble fiber is just one step in following a heart-healthy diet that can help you maintain normal cholesterol levels, lower cholesterol levels, if necessary, and reduce your risk of developing heart disease. The American Heart Association notes that soluble fiber helps lower blood cholesterol when it is included in a diet that is low in cholesterol and low in fat, especially saturated and trans fats, which are considered the most harmful fats.
References
- National Heart Lung and Blood Institute: National Cholesterol Education Program--Third Report of the Expert Panel on Detection, Evaluation, and Treatment of the High Blood Cholesterol in Adults
- University of Maryland Medical Center: Fiber
- University of Arizona Cooperative Extension: Dietary Fiber
- Harvard University Health Services: Fiber Content of Foods in Common Portions
- American Heart Association: Cholesterol, Fiber and Oat Bran
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