Fiber is a type of carbohydrate. Plant-derived foods—such as fruits, vegetables, and whole grains—all contain fiber. There are two types of dietary fiber: soluble and insoluble. Both types of fiber are important. Soluble fiber helps block cholesterol and fats from being absorbed into the bloodstream. Insoluble fiber helps prevent constipation.
Both types of fiber increase feelings of fullness, which may help maintain a healthy weight. Diets too low in fiber can contribute to heart disease, type-2 diabetes, and diverticulitis (inflammation of the intestines).
Fiber is contained in the seeds of wheat, oats, barley, rice (brown), and other grains. Whole-grain foods contain the entire grain seed, which is made up of an outer layer (bran), the middle layer (endosperm), and the inner layer (germ).
When wheat is processed into white flour, the bran and the germ are removed, along with the fiber and other nutrients. As a result, foods made with refined grains (e.g., white flour) contain less fiber and other important nutrients.
Fruits and vegetables also contain fiber, usually between 1 and 5 grams per serving. Fruits such as apples, oranges, and peaches contain soluble fiber, and vegetables such as green beans, cauliflower, and celery contain insoluble fiber.
Eating whole pieces of fruit rather than drinking fruit juice is the best way to get the full amount of fiber. Five servings a day of fruits and vegetables are recommended.
The recommended daily amount of fiber for adults is 20–35 grams. For children, the recommended daily amount is equivalent to the child's age plus 5 (for example, a 10-year old child should get at least 15 grams of fiber a day).
To get the recommended amount (Daily Value, or DV) of fiber, it is important to choose whole grain products and fresh fruits and vegetables as often as possible. Incorporating lentils and beans into the diet will also increase the amount of fiber.
To ensure that a food is made from whole grain, the term "whole grain" should be the first or second ingredient listed. Also, check the Nutrition Facts label for the amount (in grams) of fiber and for the %DV (percent daily value) of fiber. Products made with whole grains should have 2.5 grams or more of fiber per serving, which is equal to 10% or more of %DV.
To add more fiber to the diet:
- Buy whole-grain bread with a minimum of 2.5 grams of fiber per serving.
- Check for whole grains in the ingredients lists of all grain-based products.
- Choose breakfast cereals made with whole grains (containing at least 2.5 grams of fiber per serving).
- Eat brown rice instead of white rice at home and request brown rice in restaurants.
- Eat plenty of fresh fruits and vegetables.
- Have a green salad with dinner or lunch.
- Include beans, lentils, and chickpeas in the diet.
- Snack on raw vegetables instead of chips, crackers, or candy.
- Substitute lentils or beans for meat 2-3 times per week.
- Substitute whole-grain pasta for traditional pasta.
For the purpose of choosing healthy, whole-grain foods:
- An "excellent" source of fiber is a product that has 20-30% of the %DV (percent daily value) for fiber per serving (i.e., at least 5 grams per serving).
- A "good" source of fiber is a product that has 10-20% of the %DV (percent daily value) for fiber per serving (i.e., at least 2.5 grams per serving).