Insoluble or Soluble Fiber: Which Lowers Cholesterol?

Studies Show That Soluble Fiber May Help Lower Cholesterol More

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There are two types of fiber: soluble fiber and insoluble fiber. While both of these are important to include in your diet, studies have shown that one type of fiber can also help to lower your cholesterol.

We have already known some of the other healthy benefits that fiber has to offer. It helps with normal bowel function and it adds bulk to foods to make you feel fuller. However, there is evidence of another, essential benefit that fiber may have is that it can improve your heart health.

Types of Fiber

Although there are several forms of fiber, they can be classified into two major groups: soluble fiber and insoluble fiber. While both are good for the body, only one group has been shown to be beneficial in lowering your cholesterol.

Soluble fiber can be dissolved in water and forms a gel-like consistency in the digestive tract. On the other hand, insoluble fiber cannot be dissolved in water, so it passes through the digestive tract relatively unchanged. When it comes to your heart health, it appears that only soluble fiber is beneficial in lowering your cholesterol. In fact, studies have shown that consuming 10 to 25 grams soluble fiber a day can lower cholesterol by 18%.

However, it appears to only lower your “bad” cholesterol (LDL) –- your “good” cholesterol (HDL) and triglycerides are only minimally, if at all, affected by soluble fiber. Additionally, insoluble fiber does not appear to affect cholesterol levels, but it is important in maintaining a healthy colon.


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. In studies to date, LDL cholesterol can decrease by at most 18% by consuming roughly 30 grams of soluble fiber daily.

The other type of fiber, insoluble fiber, is also in many healthy foods. While this type of fiber also appears to have many health benefits, it does not lower cholesterol levels.  


Where Can I Get Soluble Fiber?

A variety of foods contain soluble fiber. By consuming the recommended amounts of fruits, vegetables, whole grains, and legumes in the Food Pyramid, you should be able to obtain the recommended amount of soluble fiber each day.

While fiber supplements can be used to fulfill this requirement, it is not recommended that you use them as substitute for eating a healthy diet.

Fruits and vegetables also contain important nutrients, such as vitamins, that cannot be obtained through a fiber supplement.



Rolfes SR, Whitney E. Understanding Nutrition, 3rd ed 2005.

Poli A, Marangoni F, Paoletti R, et al. Non-pharmacological control of plasma cholesterol levels. Nutr Metab Cardiovas Dis 2008; 18:S1-S16.

Brown L, Rosner B, Willett WW, et al. Cholesterol-lowering effects of dietary fiber: a meta-analysis. Am J Clin Nutr 1999; 69:30-42.

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.

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