The Many Health Benefits of Fiber

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Many people know that they should consume more fiber to help relieve constipation or diarrhea. But a high-fiber diet is important for everyone. The term "dietary fiber" includes two types of fiber found in plant-based foods.

Dietary fiber, or roughage, promotes several health benefits in addition to bowel regularity. These include better control of cholesterol and blood sugar, lowering risk of diabetes or heart disease, aiding in weight loss, and preventing obesity, and even reducing the risk of cancer.

Different Types of Fiber

Dietary fiber is found in all plant-based foods, including whole grains, fruits, vegetables, nuts, and legumes (beans, peas, and lentils). Although it is considered a carbohydrate, dietary fiber is different from other carbohydrates which are broken down into sugar molecules.

Dietary fiber is not digestible, meaning that it travels through the body without being broken down the way enzymes break down other food substances, such as proteins, sugars, fats, and other types of carbohydrates.

Soluble Fiber

Soluble fiber can dissolve in water. This type of fiber is found in oats, beans, nuts, peas, lentils, flaxseed, and barley, as well as in the soft parts of fruits such as apples, blueberries, grapes, prunes, and citrus fruits.

As soluble fiber passes through the digestive tract, the fiber absorbs water to become a gel-like substance. It helps relieve diarrhea by soaking up extra water, firming up the consistency of stool, and slowing down the speed that food travels through the digestive tract.

Soluble fiber also plays an important role in how the body digests sugars and starches. It creates short-chain fatty acids, which send signals to the liver to stop producing glucose.

This reduces the amount of insulin required to stabilize blood sugars and can reduce glucose intolerance. In people who already have type 1 or 2 diabetes, consuming a diet high in soluble fiber can reduce the amount of insulin required to maintain a healthy blood sugar level.

Consuming soluble fiber (the kind that gels) on a regular basis can lower blood glucose and decrease the risk of developing type 2 diabetes.

In addition, soluble fiber promotes heart health through its role in lowering cholesterol. As soluble fiber travels through the digestive tract, it binds to bile acids and cholesterol, which are then eliminated with the fiber. Over time, this leads to lowering LDL (low-density lipids, or “bad cholesterol”) in the blood, which can reduce the risk of heart disease or stroke.

Insoluble Fiber

Insoluble fiber is the type of fiber that does not dissolve in water. As it passes through the digestive tract, insoluble fiber adds bulk, or weight, to the stool. Although it is not a laxative, insoluble fiber promotes optimal motility of the digestive tract, which can relieve constipation and encourage timely elimination of wastes found in the colon.

Insoluble fiber also softens the stool, easing the passage of bowel movements and decreasing the need for straining, which can help in both the prevention and treatment of hemorrhoids.

Insoluble fiber is found in wheat, rye, brown rice, legumes, and nuts as well as in the cells of plant walls. Green, leafy vegetables, as well as the skins and peels of most fruits and vegetables, are excellent sources of the insoluble fiber found in plant walls. 

Dietary fiber also plays a role in both weight loss and preventing obesity. Since foods that are high in dietary fiber typically leave you feeling more satisfied and full, you may eat less, leading to weight loss over time.

Many high-fiber foods are also low on the glycemic index, which is a scale that ranks how much a food will impact blood sugar levels. This results in fewer sugar spikes, which helps to prevent constant cravings and acts as a natural appetite suppressant.

High-fiber foods are usually less energy-dense, meaning that they have fewer calories for the same volume of food when compared to low fiber foods. 

High-fiber diets have also been studied for their role in preventing cancer. While researchers are still studying a possible connection to colon cancer, recent studies have found a link to breast cancer. Researchers have reported that a higher fiber intake among females during the teenage and young adult years is associated with a lower risk of developing breast cancer. 

Guidelines for Fiber Intake

According to the Academy of Nutrition and Dietetics, the recommended daily intake of dietary fiber varies depending on age and gender, ranging from 21 to 38 grams per day. However, the USDA estimates that most Americans fall short of the guidelines and average only about 15 grams per day.

Recommended Daily Dietary Fiber Intake

Gender

Under 50 Years Old

Over 50 Years Old

Female

25 grams per day

21 grams per day

Male

38 grams per day

30 grams per day


Although most plant-based foods contain both soluble and insoluble fiber, nutrition labels typically list the total amount of dietary fiber found in each serving vs. specifying the amount of fiber type.

While both types of fiber play an important role in promoting optimal health, the focus should be on the total dietary fiber consumption meeting the daily recommended intake, with an effort to include as many sources of dietary fiber to the diet as possible.

How to Increase Your Fiber Intake

Focus on boosting your consumption of plant-based foods, and you'll add to your daily fiber tally. Keep in mind that it may be best to gradually increase fiber intake to prevent cramping, bloating or gas, which can be common when too much fiber is added too quickly.

  • Add kidney, pinto or black beans to soups and salads.
  • Add wheat bran or oats to yogurt or smoothies and also when baking muffins, cakes, or cookies.
  • Aim for at least five servings of fruits and vegetables per day, opting for fresh or frozen vs. canned (canned fruits are lower in fiber).
  • Choose a breakfast cereal with whole grains listed as the first ingredient.
  • Choose snacks such as dried fruits and nuts, or granola bars with fiber added.
  • Replace white rice, bread, and pasta with whole grain products and brown rice.

Another way to increase dietary fiber is by taking a daily supplement. However, keep in mind that supplements do not offer the same types of fibers, vitamins, minerals, and other nutrients as a healthy diet consumed from a variety of whole foods rich in dietary fiber.


As you begin to add more dietary fiber to your diet, remember to drink plenty of water. Experts now recommend that individuals drink the equivalent of half their body weight in ounces of water each day.

For example, this means that someone weighing 150 pounds should drink 75 ounces of water per day. Meeting the recommended water intake will help dietary fiber work best as it travels through the digestive tract.

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  1. Dahl WJ, Stewart ML. Position of the Academy of Nutrition and Dietetics: Health implications of dietary fiberJ Acad Nutr Diet. 2015;115(11):1861-70. doi:10.1016/j.jand.2015.09.003

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