What Is Fiber?

Fiber is a carbohydrate only found in plant foods like vegetables, fruits, beans, whole grains, seeds and nuts. Fiber is made up of many sugar molecules. Dietary fiber cannot be broken down and digested in our bodies.

What Are the Different Types of Fiber?

There are 2 different types of fiber:

  • Soluble fiber dissolves in water and forms a gel-like substance in the stomach. It is broken down by bacteria in the large intestine and provides some calories.
  • Insoluble fiber does not dissolve in water. It passes through the gastrointestinal tract (a system of organs that helps digest food, such as the esophagus, stomach and intestines) intact. In soluble fiber is not a source of calories.

How Much Fiber Do I Need Every Day?

Most people need between 25-38 grams (g) of fiber every day. This is also called the Daily Recommended Value. How much fiber you need depends on how many calories you need every day.

Tips to Add More Fiber to Your Diet

  • Look for foods that have 3 or more grams of fiber per serving.
  • Look for 100% WHOLE grains first on ingredient list. Examples are brown rice, barley, quinoa, rolled oats, bulgur, millet, oatmeal, spelt, whole rye or whole wheat.
  • Know how ingredients are listed. Ingredients are listed by weight. The closer an ingredient is to the top of the list, the more of that ingredient there is in that food.
  • Enjoy refined grains (processed sugars) as a treat once in a while. This includes foods such as cakes, chips, cookies and crackers
  • Choose fruit for snacks, salads or desserts.
  • Make quick, fiber-filled snacks with raw, cut-up vegetables such as broccoli florets, carrots and red peppers.
  • Add unsalted nuts, seeds, beans (garbanzo, kidney, black beans), lentils or peas to salads, soups and side dishes.
  • Consider adding a fiber supplement to your favorite drink. Fiber supplements are best for short-term use or until you are no longer constipated. It is best to get fiber from food. Fiber supplements do not have the nutrients, vitamins or minerals your body needs to work properly.

What Does Fiber Do?

Both types of dietary fiber help prevent constipation and help you feel full, so you stay satisfied for longer. They can also lower your risk of developing heart disease and diabetes later in life.

Soluble fiber helps with:

  • How well your body absorbs dietary fat and cholesterol
  • Helps lower blood cholesterol
  • Slows down how quickly your stomach empties
  • Slows digestion and how quickly your body absorbs carbohydrates into your bloodstream. This helps control blood glucose (blood sugar) by keeping your blood sugar levels more stable.

Insoluble fiber helps with:

  • When combined with drinking plenty of water, insoluble fiber helps make your stool soft and bulky
  • Speeds up the movement of food and waste through the digestive system
  • Helps prevent hemorrhoids (swollen veins in your anus, just inside your bottom) and diverticulosis (when small pouches or pockets in the walls of the intestines bulge into the colon, or large intestine)

Which Foods Have High Amounts of Fiber?

Foods with Soluble Fiber

  • Beans, lentils and peas (also called legumes)
  • Vegetables (especially Brussels sprouts, sweet potatoes, asparagus)
  • Fruits (especially oranges, apricots, apples and pears)
  • Oats (like oatmeal and oat bran)
  • Nuts and seeds (especially flax seeds and chia seeds)

Foods with Insoluble Fiber

  • Vegetables (peas, carrots, broccoli, kale, sweet potatoes, bell peppers)
  • Fruits, unpeeled (berries, apples, pears, plums, apricots)
  • Nuts and seeds (almonds, walnuts, sunflower seeds, peanuts, hazelnuts)
  • Whole grains (like brown rice, 100% whole grain breads, pastas and cereals)
  • Wheat bran, oat bran, corn bran or quinoa
  • Beans and legumes (black beans, garbanzo beans, pinto beans, kidney beans, lentils)

What Does 25g of Fiber Look Like?


  • Bran or whole grain cereal (5g of fiber) with half of a sliced banana (1.5g) and skim milk


  • 24 almonds (2.5g) and ¼ cup of raisins (2g)


  • Sliced turkey sandwich on whole grain bread with lettuce and tomato (5g). An orange (3g).


  • Yogurt with ½ cup of blueberries (2g)


  • Grilled fish with a salad of romaine lettuce, shredded carrots (3g) and ½ cup of cooked spinach (2g).

Did You Know...?

Fewer than 3 out of 10 Americans get the minimum recommended daily amount of fiber. On average, most people only get 15 grams (g) of fiber a day.

Rev. 4/2019. Created by Judith Sharlin, PhD, RD. Mass General for Children and Massachusetts General Hospital do not endorse any of the brands listed on this handout. This handout is intended to provide health information so that you can be better informed. It is not a substitute for medical advice and should not be used to treatment of any medical conditions.