Here's a fiber fact sheet from kaiserpermanente.org.
Why is fiber important?
Including fiber in your diet is good for your health in lots of ways. A diet rich in high fiber foods can:
• reduce the risk of heart disease and type 2 diabetes
• lower the risk of several forms of cancer
• improve cholesterol and blood pressure
• help regulate your digestion
• help you feel fuller, so you may eat less
What exactly is fiber?
Fiber is the part of plant foods that our bodies can’t absorb or digest. It is found in fruits, vegetables, beans, peas, lentils, nuts, seeds, and whole grains. Fiber is also known as roughage or bulk. There are two kinds of dietary fiber: insoluble and soluble. It is important to eat plenty of both.
Insoluble fiber comes from fruits, grains, and vegetables. It adds bulk and acts like a brush to clean out the colon. As it passes through the digestive tract, insoluble fiber remains mostly intact. This helps keep your bowel movements regular.
Soluble fiber comes from fruit, some vegetables, oats, beans, peas, lentils, and barley. When mixed with liquid, it forms a gel, which helps control blood sugar and reduces cholesterol.
What is a whole grain?
A whole grain has all three of its original parts: the bran (fiber-rich outer layer), the germ (inner layer), and the endosperm (middle layer). Whole grains are rich in nutrients, including fiber. Whole wheat flour, oatmeal, rye, cornmeal, bulgur, barley, brown rice, and even popcorn are all whole grains.
A refined grain has been milled, so only the middle layer (endosperm) is left. Milling removes much of the vitamins, iron, protein, and fiber. “White” and “wheat” flours are refined grains. “Enriched” flour has had some of the nutrients added back, but not the fiber. White rice is also a refined grain.
How much fiber do I need?
The American Heart Association recommends between 25 and 38 grams of fiber a day in a well-balanced diet. The average American eats only 15 grams of fiber a day.
Adding more fiber to your diet
1. Eat at least 5 servings of fruits and vegetables every day. Eat the skins and peels whenever you can, because they contain a lot of fiber.
2. Try more recipes with beans, peas, lentils, quinoa, bulgur, or brown rice.
3. Eat oatmeal, bran, or another whole grain cereal for breakfast.
4. Choose breads, cereals, tortillas, and crackers that list a whole grain as the first ingredient on the label.
5. Make at least half of your grain servings whole grains.
6. Add fiber to your diet slowly. If you add it too fast, you may feel bloated or have gas pains.
7. Unless your doctor has told you not to, drink 6 to 8 cups of water and other fluids a day to keep things moving smoothly through your intestines.
8. If you eat wheat bran to keep your bowels moving, start with 1 teaspoon per meal. Increase slowly to 2 to 4 tablespoons a day.
9. Buy unprocessed foods when you can. Food processing often removes fiber.
Read food labels
Look for the “dietary fiber” content on food labels. Good sources of fiber have at least 10% of the “percent daily value” for fiber. When looking for whole grain products, read the ingredient list.