What Is Fiber?

Dietary fiber is a form of carbohydrate found in plants that cannot be digested by humans. All plants contain fiber, including fruits, vegetables, grains, and legumes. Fiber is often classified into two categories: soluble and insoluble.

  • Soluble fiber draws water into the bowel and can help slow digestion. Examples of foods that are high in soluble fiber include oatmeal, oat bran, barley, legumes (eg, beans and peas), apples, and strawberries.
  • Insoluble fiber speeds digestion and can add bulk to the stool. Examples of foods that are high in insoluble fiber include whole-wheat products, wheat bran, cauliflower, green beans, and potatoes.
Why Follow a High-Fiber Diet?

A high-fiber diet is often recommended to prevent and/or treat constipation, hemorrhoids, diverticulitis, irritable bowel syndrome, and colon cancer.

Eating a high-fiber diet can also help improve your cholesterol levels, lower your risk of coronary heart disease, reduce your risk of type 2 diabetes, and lower your weight. For people with type 1 or 2 diabetes, a high-fiber diet can also help stabilize blood sugar levels.

How Much Fiber Should I Eat?

A high-fiber diet should contain 20-35 grams of fiber a day. This is actually the amount recommended for the general adult population; however, most Americans eat only 15 grams of fiber per day.

Digestion of Fiber

Eating a higher fiber diet than usual can take some getting used to by your body’s digestive system. To avoid the side effects of sudden increases in dietary fiber (eg, gas, cramping, bloating, and diarrhea), increase fiber gradually and be sure to drink plenty of fluids every day.

Tips for Increasing Fiber Intake
  • Whenever possible, choose whole grains over refined grains (eg, brown rice instead of white rice, whole-wheat bread instead of white bread).
  • Include a variety of grains in your diet, such as wheat, rye, barley, oats, quinoa, and bulgur.
  • Eat more vegetarian-based meals. Here are some ideas: black bean burgers, eggplant lasagna, and veggie tofu stir-fry.
  • Choose high-fiber snacks, such as fruits, popcorn, whole-grain crackers, and nuts.
  • Make whole-grain cereal or whole-grain toast part of your daily breakfast regime.
  • When eating out, whether ordering a sandwich or dinner, ask for extra vegetables.
  • When baking, replace part of the white flour with whole-wheat flour. Whole-wheat flour is particularly easy to incorporate into a recipe.
High-Fiber Diet Eating Guide
Food CategoryFoods RecommendedNotes
Grains
  • Whole-grain breads, muffins, bagels, or pita bread
  • Rye bread
  • Whole-wheat crackers or crisp breads
  • Whole-grain or bran cereals
  • Oatmeal, oat bran, or grits
  • Wheat germ
  • Whole-wheat pasta and brown rice
  • Read the ingredients list on food labels. Look for products that list "whole" as the first ingredient (eg, whole-wheat, whole oats).
  • Choose cereals with at least 2 grams of fiber per serving.
Vegetables
  • All vegetables, especially asparagus, bean sprouts, broccoli, Brussels sprouts, cabbage, carrots, cauliflower, celery, corn, greens, green beans, green pepper, onions, peas, potatoes (with skin), snow peas, spinach, squash, sweet potatoes, tomatoes, zucchini
  • For maximum fiber intake, eat the peels of fruits and vegetables—just be sure to wash them well first.
Fruits
  • All fruits, especially apples, berries, grapefruits, mangoes, nectarines, oranges, peaches, pears, dried fruits (figs, dates, prunes, raisins)
  • Choose raw fruits and vegetables over juice, cooked, or canned—raw fruit has more fiber. Dried fruit is also a good source of fiber.
Milk
  • With the exception of yogurt containing inulin (a type of fiber), dairy foods provide little fiber.
  • Add more fiber by topping your yogurt or cottage cheese with fresh fruit, whole grain or bran cereals, nuts, or seeds.
Meats and Beans
  • All beans and peas, especially Garbanzo beans, kidney beans, lentils, lima beans, split peas, and pinto beans
  • All nuts and seeds, especially almonds, peanuts, Brazil nuts, cashews, peanut butter, walnuts, sesame and sunflower seeds
  • All meat, poultry, fish, and eggs
  • Increase fiber in meat dishes by adding pinto beans, kidney beans, black-eyed peas, bran, or oatmeal.
  • If you are following a low-fat diet, use nuts and seeds only in moderation.
Fats and Oils
  • All in moderation
  • Fats and oils do not provide fiber
Snacks, Sweets, and Condiments
  • Fruit
  • Nuts
  • Popcorn, whole-wheat pretzels, or trail mix made with dried fruits, nuts, and seeds
  • Cakes, breads, and cookies made with oatmeal or whole-wheat flour
  • Most snack foods do not provide much fiber. Choose snacks with at least 2 grams of fiber per serving.