Fiber is a type of carbohydrate found in plant products and is divided in two types based on water solubility.
Soluble fiber dissolves in water, forms a gel-like material, and is found mainly in oats, apples, citrus, peas, barley, pectin, flaxseed, guar, and beans.
Whole wheat flour, wheat bran, cellulose, lignin, nuts, and many vegetables contain insoluble fiber.
Large studies have shown that increased fiber intake, especially water-SF, is associated with a decrease in coronary heart disease risk.
An analysis of ten studies detected a 12% reduction in the risk for coronary events and a 19% reduction in the risk of coronary deaths for each 10 g increment in dietary fiber per day.
How to reduce cholesterol
The studies suggest that the fiber can bind bile acid, which leads to increased bile acid production, reduction of liver cholesterol content, up-regulation of low density lipoprotein (LDL) receptors, and increase LDL clearance. Steps are as follows,
Fiber binds bile acid
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Liver increases bile acid production using liver cholesterol content
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The number of LDL cholesterol receptors of the liver increases
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More blood cholesterol enters the liver
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Blood cholesterol goes down
Insoluble fiber doesn’t appear to have any significant effect on LDL-Cholesterol (LDL-C).
In fact, studies have shown a significant (approximately 5-7%) reduction of LDL-C due to the consumption of soluble fiber.
Fiber intake does not change the levels of triglycerides or high density lipoproteins (HDL).
Sources of Dietary Fiber
| Water Soluble (Good for Cholesterol Reduction) | Water Insoluble (Good for Bowel Movement) |
| Oats | Whole Wheat Flour |
| Apples | Wheat Bran |
| Citrus | Cellulose |
| Peas | Lignin |
| Barley | Nuts |
| Pectin | Vegetables |
| Flaxseed | |
| Beans | |
| Guar | |
| Psyllium |
How Much Fiber Should be Consumed?
The National Cholesterol Education Program recommends an intake of 5 to 10 g of soluble fiber per day to improve LDL-C levels.
The American Heart Association (AHA) recommends a total dietary fiber intake of 25 to 30 g/d from foods, not supplements, to ensure nutrient adequacy and maximize the cholesterol-lowering impact of a fat-modified diet.
Current dietary fiber intakes among adults in the United States average about 15 g, or half the recommended amount.
Eating two small apples, one cup of green peas, and one-half cup of pinto beans can deliver 10 g of soluble fiber to your body.
Side Effects of Fiber
Fiber consumption could cause bloating. Less fermented fibers, such as psyllium result in less bloating.
Drinking sufficient amounts of fluid and slowly increasing the amount of fiber intake could also limit bloating.
Individuals with irritable bowel syndrome cannot tolerate increased fiber consumption and need to limit their intake.
High fiber intake could interfere with the absorption of minerals, such as iron, zinc, magnesium, and calcium.
Pros and Cons of Fiber
Pros
- Widely accessible, also in unprocessed form
- Research-based evidence support the usage
- No major side effects
Cons
- Choice of the proper kind of fiber is important
- Could have annoying side effects such as bloating
- Increase amount of fiber consumption could interfere with absorption of minerals
- Low intake of fiber will not result in any noticeable LDL-C reduction
Conclusion
Fiber intake is beneficial in reducing LDL cholesterol. A 5-7% reduction of LDL-C can be expected from the consumption of 5-10 g of SF per day.
