Dietary Fiber Definition, Benefits, Importance

What is Dietary Fiber

Fiber comes from plants and includes such things as cellulose, pectin and gums.

They are the indigestible part of plant foods that move through the digestive system, absorbing water and easing the passage of waste products.

Soluble or Non-Soluble Dietary Fiber?

Most dietary fiber is classified as to whether it is water soluble or not and both types are present in all plant foods, with varying degrees of each according to the plant’s characteristics.

Insoluble fiber has passive water-attracting properties that help to increase bulk, soft stool and shorten transit time through the intestinal tract.

Soluble fiber undergoes metabolic processing via fermentation, yielding end-products with broad, significant health effects.

For example, plums (or prunes) have a thick skin covering its juicy pulp. The plum’s skin is an example of an insoluble fiber source, whereas soluble fiber sources are inside the pulp. So with prunes we get a double benefit on the issue of colon health.

Other sources of insoluble fiber include whole wheat, wheat and corn bran, flax seed and vegetables such as celery, green beans, potato skins and tomato peel. Some sources of soluble fibers are peas, beans, oats, apples and carrots.

It is estimated that North Americans consume less than 50% of the dietary fiber levels required for good health.

In the preferred food choices of today’s youth, this value may be as low as 20%, a factor considered by experts as contributing to the obesity crisis we see in our young people.

The FDA Steps In

In view of the growing scientific evidence for physiological benefits of increased fiber intake, the FDA is now allowing food producers to make health claims for dietary fiber.

We were all wondering how those cereal manufacturers could get away with selling pharmaceuticals in a box. After all, only an FDA approved drug can make health claims, or so we thought. Wonder what that cost the cereal companies?

Cold breakfast cereal, National Cancer Institute

In clinical trials, these fiber sources were shown to significantly reduce blood cholesterol levels, an important factor for general cardiovascular health, and to lower risk of onset for some types of cancer.

Soluble (fermentable) fiber sources gaining FDA approval are:

  • Psyllium seed husk (7 grams per day)
  • Beta-glucan from oats (3 grams per day)
  • Beta-glucan from whole grains or barley (3 grams per day)

Consistent intake of fermentable fiber through foods like berries and other fresh fruit, vegetables, whole grains, seeds and nuts is now known to reduce risk of some of the world’s most prevalent diseases — obesity, diabetes, high blood cholesterol, cardiovascular disease, and numerous gastrointestinal disorders.

It turns out that fiber does much more than just absorbing water and helping the colon to rid of fecal matter. The more important function is that it feeds the 100 trillion or so bacteria in our gut that comprise the microbiome.

If we don’t eat enough complex carbohydrate fiber, then the bacteria get hungry and start to feed off the mucus in our GI tract, which brings them closer and closer to our intestinal lining, which in turn triggers an autoimmune reaction which leads to many of the disease conditions mentioned.

Yes, there is an incredible relationship and interaction between fiber, the microbes of the microbiome, the immune system and health. It’s time to get educated and take control of your health.

Fermentable fiber can provide healthful benefits for constipation, inflammatory bowel disease, ulcerative colitis, hemorrhoids, Crohn’s disease, diverticulitis, and colon cancer — all disorders of the intestinal tract.

Insufficient fiber in the diet can complicate defecation. Low-fiber feces are dehydrated and hardened, making them difficult to evacuate. This is actually the definition of constipation and, as many of us know too well, can lead to development of hemorrhoids or anal fissures.

How much dietary fiber do we need and where do we get it?

The American Dietetic Association recommends a minimum of 20-35 g/day for a healthy adult depending on calorie intake. The ADA’s recommendation for children is that intake should equal their age in years plus 5 g/day, for example, a 4 year old should consume 9 g/day.

The top dietary fiber plant foods, according to the Linus Pauling Institute, are legumes (15-19 grams of fiber per US cup serving, including several types of beans, lentils and peas), wheat bran (17 grams per cup), prunes (12 grams), and Asian pear (10 grams each, 3.6% by weight).

In the event anyone has a need to know the fiber content of various foods, Continuum Health Partners (CHP), a non-profit hospital system in New York City has a pretty decent fiber chart that can be accessed by clicking on CHP Dietary Fiber Chart.

Soluble fiber is found in varying quantities in all plant foods, including:

  • oats, rye, chia and barley
  • some fruits and fruit juices, especially prune juice
  • vegetables such as broccoli, carrots and artichokes
  • root vegetables such as potatoes, sweet potatoes, and onions
  • psyllium seed husk (a mucilage soluble fiber)

Sources of insoluble fiber include:

  • whole grain foods
  • bran
  • nuts and seeds
  • vegetables such as green beans, cauliflower, and zucchini
  • the skins of some fruits, including tomatoes

The top dietary fiber plant foods, according to the Linus Pauling Institute, are legumes (15-19 grams of fiber per US cup serving, including several types of beans, lentils and peas), wheat bran (17 grams per cup), prunes (12 grams), and Asian pear (10 grams each, 3.6% by weight).

So put your prunes on your cereal, sprinkle with flax, add a few blueberries and strawberries and have a marvellous day.