Soluble fiber plays an important role in daily nutrition. It can help lower LDL cholesterol levels in the body and prevent the overproduction of bile.

Foods contain two different types of fiber: soluble and insoluble. Soluble fiber, such as pectin and gum inside plant cells, dissolves in water and forms a gel-like paste.

During digestion, soluble fiber binds with cholesterol in bile and aids in its excretion, which lowers the amount of cholesterol in the body.

This article discusses the effects of soluble fiber on cholesterol levels and bile production. It looks at foods that provide people with their recommended daily soluble fiber intake. Plus, it includes the difference between soluble and insoluble fiber and tips for maintaining healthy cholesterol levels.

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Soluble fiber has numerous functions. One of these is it binds or traps cholesterol, carrying it through the digestive tract and eliminating it via the colon.

There are two main types of cholesterol: low-density lipoprotein (LDL) and high-density lipoprotein (HDL). These are typically known as “bad” and “good” cholesterol. Cholesterol travels through the blood on proteins called lipoproteins.

HDL cholesterol absorbs cholesterol and carries it back to the liver. High levels of HDL cholesterol can lower the risk of heart disease and stroke.

LDL cholesterol makes up most of the cholesterol in the body. High levels of LDL cholesterol raise the risk of heart disease and stroke because it causes a buildup of plaque on the walls of the blood vessels.

Over time, this buildup increases, and the insides of the blood vessels begin to narrow, blocking the blood flow to and from the heart and other organs. This blocking can cause angina or a heart attack.

It is, therefore, necessary to eliminate excess LDL cholesterol from the body. People with high levels of LDL due to their diet can achieve this by increasing their intake of soluble fiber.

Plant foods contain soluble fiber, also known as viscous fiber because it absorbs water to form a thick, gelatin-like substance.

Soluble fiber interferes with the absorption of dietary fat and cholesterol by binding with these two substances and carrying them through the digestive tract.

Another function of soluble fiber is interacting with bile acids by absorbing them, preventing their reabsorption, and excreting them into the colon.

Cholesterol from the liver synthesizes bile acids in the gallbladder.

Bile is a watery solution. It consists of bile salts, phospholipids, cholesterol, conjugated bilirubin, electrolytes, and water. Its main function is to absorb fats and remove waste products from the body.

When people eat food, the gallbladder contracts and releases bile salts. Bile salts function as a cleaning mechanism that enables the absorption of lipids and vitamins.

Soluble fiber reduces the rate at which the body reabsorbs bile acid, affecting how much bile acid it produces. This increases the synthesis of primary bile acid from cholesterol and changes the composition of the bile acid pool, which lowers the development of bile acid-related diseases such as acid reflux, gallstones, and tumors.

Adding 5–10 grams (g) of soluble fiber per day to a diet may lower cholesterol by 5–11 points.

According to the Food and Drug Administration (FDA), adults should aim to have 28 g of combined soluble and insoluble fiber per day. This amount varies depending on a person’s age and sex.

The Dietary Guidelines for Americans suggest the following:

Amount per day (g)
females under 50 years of age25–28 g
females 51 years of age and above22 g
males under 50 years of age31–34 g
males 51 years of age and above28 g

Children aged 1–18 years should eat 14–31 g per day.

About 6–8 g of total fiber intake should include soluble fiber.

The following foods are high in soluble fiber:

  • Whole grains: barley, oatmeal, oat bran, and quinoa
  • Lean protein foods: beans, such as black-eyed peas, chickpeas, black beans, and kidney beans
  • Healthy fats: avocado, whole chia seeds, and ground flax seeds
  • Vegetables: broccoli, Brussels sprouts, cabbage, and carrots
  • Starchy vegetables: sweet potatoes and green peas
  • Fruits: apples, bananas, guava, and oranges

Both types of dietary fiber, soluble and insoluble, are indigestible, so they pass through the digestive system relatively intact. Many fiber-rich foods contain both soluble and insoluble fiber.

Soluble fiber easily dissolves in water. When it reaches the colon, it breaks down into a gel-like substance.

Insoluble fiber does not dissolve in water and is left intact as food moves through the gastrointestinal tract. It adds bulk to bowel movements. It supports insulin sensitivity and helps keep the bowels healthy.

Examples of foods high in insoluble fiber are:

  • whole wheat flour
  • bran
  • nuts
  • seeds
  • skins of fruits and vegetables

People can have both high LDL and low HDL cholesterol levels.

The Centers for Disease Control and Prevention (CDC) recommend the following to help manage cholesterol levels:

  • taking any cholesterol-lowering medication a doctor prescribes
  • making healthy eating choices, such as limiting foods high in saturated fats and eating foods naturally high in fiber
  • staying physically active
  • quitting smoking, if applicable, to reduce the hardening of the arteries and decrease the risk of heart disease
  • limiting alcohol intake, if applicable, to lower cholesterol levels and triglyceride levels in the blood

Many foods contain soluble and insoluble fiber. Soluble fiber can help lower “bad” cholesterol levels and change bile composition.

People can have both high and low levels of cholesterol. Both forms of cholesterol should be within a healthy range to prevent health complications.