What is Fiber?
In a nutrition context, fiber is material from plant origin that cannot be broken down by the normal digestive process in humans. There are 2 main types: soluble and insoluble—both are important to health.
See Fiber Chart here.
Soluble Fiber includes pectins, gums, and mucilages. This type is most often consumed in fruits and vegetables, but can also be found in grains such as oat bran and barley. Soluble fiber tends to form a gel when combined with fluids in the intestinal tract. This type of fiber is particularly important for feeding the beneficial bacteria of the colon, and for binding excess bile salts in the intestines—which limits the amount of cholesterol precursors that can be recycled back into the body's circulation.
Insoluble Fiber includes cellulose and hemicellulose. This type of fiber tends to function as structural components of plants, lignans are an example.The major dietary source of insoluble fiber in the bran component of grains, as well as seed coats. This type of fiber is particularly important for bulking the stools and stimulating regular gastrointestinal movements.
Health Benefits of Fiber:
- Fiber bulks the stools, tones the intestinal tract, and decreases transit time—which means there is less time for undesirable bacteria to act on undigested food to produce gas and potentially toxic byproducts.
- Soluble fiber delays the time it takes for food to move past the stomach and slows digestion, which maximizes the absorption of nutrients.
- Because soluble fiber binds with bile salts in the intestines and increases the rate of their excretion, they lower serum cholesterol.
- Consumption of fiber slows the absorption of glucose.
- Fiber binds to excess estrogens and helps to excrete them from the body.
The National Institute of Health recommends an intake of 35 grams of fiber per day.
Conditions where increased fiber supplementation may be indicated:
- loose stools, or constipation, or excess flatulence
- high cholesterol
- prevention of breast, cervical and ovarian cancers
- healthy fiber consumption may help prevent colon cancer
- prevention of diverticulosis
- prevention of hemorrhoids
A few cautions about fiber:
High fiber foods may contain substances which can decrease your absorption of certain minerals, such as iron, zinc, calcium or magnesium. Phytic acid is one such compound and it is found in the insoluble fibers of grains. The good news is that when these foods are cooked even lightly, these compounds are easily broken down. Another substance, oxalic acid, is found in green leafy vegetables such as spinach, rhubarb, collards, kale, and mustard greens. It is also broken down by cooking, even at a low heat.
Also, it is important to know that when you begin taking a fiber supplement, you must follow directions and increase your fluid consumption accordingly, or else you may become constipated and experience intestinal discomfort. It is also important to note that any dietary changes, even very beneficial ones, may cause a temporary increase in gas and bloating until your body adjusts—very often 2-3 weeks. Make sure you are well-hydrated.
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