Dietary Fiber - Essential for a Healthy Diet
Dietary fiber is the bulky part of food that cannot be broken down by enzymes in the small intestine of the digestive system. Almost all natural fiber comes from plants. Although fiber has little nutritional value, it offers other health benefits. People with a high-fiber diet experience lower rates of cancer because food passes through the body more rapidly. By adding bulk to the diet, fiber also prevents constipation, minimizes intestinal disorders, and may serve as an aid in dieting. The benefits of consuming foods high in fiber include lower blood levels of cholesterol and triglycerides. Foods high in fiber include legumes, green, leafy vegetables, whole fruits, and unrefined foods such as bran and sprouted seeds. Fiber is also known as roughage.
Some plants contain significant amounts of soluble and insoluble fiber. For example plums (or prunes) have a thick skin covering a juicy pulp. The plum's skin is an example of an insoluble fiber source, whereas soluble fiber sources are inside the pulp.
Sources of soluble fiber include:
- legumes (peas, soybeans, and other beans)
- oats, rye, and barley
- some fruits and fruit juices (including prune juice, plums, berries, bananas, and the insides of apples and pears)
- certain vegetables such as broccoli, carrots and Jerusalem artichokes
- root vegetables such as potatoes, sweet potatoes, and onions (skins of these vegetables are sources of insoluble fiber)
Sources of insoluble fiber include:
- whole grain foods
- wheat and corn bran
- nuts and seeds
- potato skins
- vegetables such as green beans, cauliflower, zucchini, and celery
- the skins of some fruits, including tomatoes
Guidelines on fiber intake
Current recommendations suggest that adults should consume 20-35 grams of dietary fiber per day, but the average
American's daily intake of dietary fiber is only 12-18 grams.
The ADA's recommendation for children is that intake should equal age in years plus 5 g/day (e.g., a 4 year old
should consume 9 g/day).
No guidelines have yet been established for the elderly or very ill. Patients with current constipation, vomiting and abdominal pain should see a physician.
What is dietary fiber?
Dietary fiber, also known as roughage or bulk, includes all parts of plant foods that your body can't digest or
absorb. Unlike other food components such as fats, proteins or carbohydrates — which your body breaks down and
absorbs — fiber isn't digested by your body. Therefore, it passes virtually unchanged through your stomach and
small intestine and into your colon.
Fiber is often classified into two categories.
Insoluble fiber. This type of fiber promotes the movement of material through your digestive system and increases
stool bulk, so it can be of benefit to those who struggle with constipation or irregular stools. Whole-wheat
flour, wheat bran, nuts and many vegetables are good sources of insoluble fiber.
Soluble fiber. This type of fiber dissolves in water to form a gel-like material. It can help lower blood
cholesterol and glucose levels. You can find generous quantities of soluble fiber in oats, peas, beans, apples,
citrus fruits, carrots, barley and psyllium.
A high-fiber diet has many benefits, which include:
- Prevents constipation. Dietary fiber increases the weight and size of your stool and softens it. A bulky
stool is easier to pass, decreasing your chance of constipation. If you have loose, watery stools, fiber may also
help to solidify the stool because it absorbs water and adds bulk to stool.
- Lowers your risk of digestive conditions. A high-fiber diet may lower your risk of specific disorders, such
as hemorrhoids and irritable bowel syndrome.
- Lowers blood cholesterol levels. Soluble fiber found in beans, oats, flaxseed and oat bran may help lower total blood cholesterol levels by lowering low-density lipoprotein, or "bad," cholesterol levels.
- Controls blood sugar levels. Fiber, particularly soluble fiber, can slow the absorption of sugar, which for
people with diabetes, can help improve blood sugar levels.
- A high-fiber diet may also reduce the risk of developing type 2 diabetes.
- Aids in weight loss. High-fiber foods generally require more chewing time, which gives your body time to
register when you're no longer hungry, so you're less likely to overeat. Also, a high-fiber diet tends to make a
meal feel larger and linger longer, so you stay full for a greater amount of time.
- High-fiber diets also tend to be less "energy dense," which means they have fewer calories for the same
volume of food.
