Dietary fibers are carbohydrates and lignin that are naturally present in plant foods and which are not digested and absorbed by the digestive system. There is also another type of fiber called functional fibers that are actually carbohydrates that have been isolated, extracted and / or purified. To be part of the range of functional fibers, they should have beneficial effects on the body. The functional fibers are not digested or absorbed by the digestive system as well as dietary fiber.
The fibers have different roles to play at the physiological level including the regularization of the gastrointestinal function, lower cholesterol levels and the management of blood glucose (sugar in the blood). They also contribute to the feeling of fullness that can help with weight management by reducing energy intake. There are also numerous studies, but not all who say a proper fiber intake protect against colon cancer.
There are two types of fiber in plant foods: soluble (viscous) and insoluble fibers. These are soluble fibers which have the property of lowering blood glucose and cholesterol levels. Insoluble fiber in turn, increase the faecal volume to regularize the intestinal function. Most plant foods contain both types of fiber. However, the amount of each type of fiber varies depending on the food.
|Food predominantly insoluble fiber||Food predominantly soluble fiber|
|Wheat bran and wheat grain||Psyllium and fortified cereals|
|Whole grains and derivatives||Oat bran cereal and oatmeal (porridge)|
|Vegetables: cauliflower, cabbage Kale, green peas, spinach, turnip greens, green beans||Legumes: kidney beans, peas|
|Fruits: raspberries, apple, pear, banana, blueberries, strawberries||Fruits: orange, grapefruit, mango, dried prunes|
|Nuts and seeds: almonds, peanuts||Vegetables: asparagus, Brussels sprouts, carrots, onion|
Daily fiber needs
Total fiber requirements have been prepared on a contribution which, according to scientific data, protects against cardiovascular disease and diabetes.
|Age||Adequate Intake (AI)|
|Babies 0 – 6 months||ND|
|Babies 7-12 month||ND|
|Babies 1-3 years||19 g|
|Children 4-8 years||25 g|
|Boys 9-13 years||31 g|
|Girls 9 to 13 years||26 g|
|Boys 14 to 18 years||28 g|
|Girl 14 – 18 years||26 g|
|Men 19-50 years||28 g|
|Women 19-50 years||25 g|
|Men 50+||30 g|
|Women 50+||21 g|
|Pregnant women||28 g|
|Nursing Women||29 g|
* Recommended Dietary Allowance
** AMT: tolerable upper intake
Dietary Fiber sources
The main sources of fiber are fruits and vegetables, and grain products, legumes and nuts.
|Cooked legumes||250 ml (1 cup)||12 – 17|
|Breakfast cereals, 100% wheat bran||30 g (1 oz)||10|
|Soybeans, fresh (edamame), boiled||250 ml (1 cup)||8|
|Raspberries||125 ml (1/2 cup)||4-6|
|Boiled artichoke||1 medium (120 g)||5|
|Prunes, cooked||75 ml pitted (80 g)||5|
|Pear with skin||1 medium (166 g)||5|
|Green peas, cooked||125 ml (1/2 cup)||4-5|
|blackberries||125 ml (1/2 cup)||4|
|Canned pumpkin||125 ml (1/2 cup)||4|
|Dates and dried figs||60 ml (1/4 cup)||4|
|Potato with skin, baked||1 medium (150 g)||4|
|Boiled spinach||125 ml (1/2 cup)||4|
|Roasted almonds in oil or dry||60 ml (1/4 cup)||4|
|Sweet potato porridge||1 medium (151 g)||4|
|Apple with peel||1 medium (138 g)||3|
|Winter squash, cooked||125 ml (1/2 cup)||3|
|Papaya||1/2 fruit (153 g)||3|
|Brussels sprouts, cooked||4 cabbage (84 g)||3|
|Blueberries||125 ml (1/2 cup)||2-3|
Tips to increase fiber intake:
- Replace refined grains with brown rice, pasta or bread made from whole grains.
- Consuming more fruits with fiber: apples and pears with their skins, raspberries and blackberries, dried fruits (prunes, apricots and dates).
- Choose mostly fiber-rich vegetables: artichokes, peas, beets, carrots, broccoli, cabbage, Brussels sprouts, corn, turnip, potatoes with the peel.
- Eating more often legumes, excellent sources of dietary fiber: white or red beans, lentils, lima beans, chickpeas.
- Add lentils or beans in soups, casseroles and salads. Cook a vegetarian chili.
- Spread hummus on a slice of whole grain bread or crackers as a snack rich in fiber.
- Snack, choose cereals rich in fiber (4 grams of fiber per serving and read) or rich in fiber muffin homemade.
- When making muffins recipes, replace white flour with whole wheat flour. Add ground flaxseed or wheat bran or oatmeal.
- Add wheat bran or oatmeal, flax seed or chia to your yogurts and compotes.
- Add soybeans in soups, stir-fries or salads.
- As a snack, eat a small handful of dried fruits and nuts.
- Read food labels and choose breads, bagels, pitas, tortillas and crackers that contain from 2 to 4 grams of fiber per serving.
It is very important to increase fiber intake gradually and drink plenty of water to avoid certain gastrointestinal symptoms.
A high fiber intake may impair the absorption of various nutrients such as calcium, magnesium, iron and zinc. By cons, when there is no deficiency in these nutrients in the diet, adequate fiber intake appear to compromise the reserves of these nutrients.
Deficiency in fiber
Since the fibers are not an essential nutrient, low intake provides no deficiency symptoms. By cons, inadequate intake of fiber can lead to constipation due to the low volume fecal.
Excessive fiber intake has no deleterious effect apart from some gastrointestinal symptoms such as bloating or gas. Overconsumption is very unlikely.
Dietary Reference Intakes, Institute of Medicine (IOM), National Academies Press, Washington, D.C., 2006.
Whitney E. Rady Rolfes S. Understanding Nutrition, 11th edition, Thomson Learning, 2008.