Fiber is the material that gives plants texture and support. Dietary fiber is found in many plant foods, including fruits, vegetables, beans, nuts, and whole grains. Although fiber is primarily made up of carbohydrates, it does not have a lot of calories and usually is not broken down by the body for energy. Fiber is sometimes called roughage.
There are two types of fiber: soluble and insoluble. Insoluble fiber, as the name implies, does not dissolve in water because it contains high amounts of cellulose. Insoluble fiber is found in grain brans, fruit pulp, and vegetable peels or skins. Soluble fiber is the type of fiber that dissolves in water. It can be found in a variety of such fruits, grains, and vegetables as apples, oatmeal and oat bran, rye flour and dried beans.
Although the two types of fiber share some common characteristics such as being partially digested in the stomach and intestines and being low in calories, each type has its own specific health benefits. Insoluble fiber speeds up the movement of foods through the digestive system and adds bulk to the stools; it helps to treat constipation or diarrhea and prevents colon cancer.
On the other hand, only soluble fiber can lower blood cholesterol levels. This type of fiber works by attaching itself to the cholesterol so that it can be eliminated from the body. This process prevents cholesterol from recirculating and being reabsorbed into the bloodstream.
High-fiber diet therapy is actually a return to nature and the plant-based diets used by our ancestors since the beginning of time. In fact, our ancestors consumed large quantities of fiber-containing foods such as fruits, vegetables and whole grain products every day.
As technology advanced, however, people began to turn away from these unprocessed healthful foods and began eating more highly processed and fat-laden foods. As a result, the incidence of coronary heart disease, diabetes, and cancers has steadily risen.
Naturopathic physicians, who practice natural healing methods, have long advocated high-fiber diets as a major preventive and therapeutic treatment for these and other diseases. Extensive medical research has now confirmed that a high-fiber diet prevents or treats a wide variety of diseases ranging from constipation to heart disease and cancer.
A high-fiber diet helps prevent or treat the following health conditions:
- High blood cholesterol levels. Fiber effectively lowers blood cholesterol levels. It appears that soluble fiber binds to the cholesterol molecule and moves it through the digestive tract so that it can be excreted from the body. This mechanism prevents cholesterol from being reabsorbed into the bloodstream. In 2003, research confirmed the long-term effects of high-fiber diets on lowering bad cholesterol in people with Type II diabetes.
- Constipation. A high-fiber diet is a useful non-drug treatment for constipation. Fiber in the diet adds more bulk to the stools, making them softer. Fiber also shortens the length of time that foods remain in the digestive tract. It is important, however, for people increasing their fiber intake to drink more water as well, in order to get the benefit of using dietary fiber to relieve constipation.
- Hemorrhoids. Fiber in the diet adds more bulk and softens the stool, thus reducing the pain and bleeding associated with hemorrhoids.
- Diabetes. A common problem for diabetics is the rapid rise of insulin levels following meals. Soluble fiber in the diet delays the emptying of the stomach contents into the intestines. This delay helps to slow the rise of blood sugar levels following a meal and thus gives diabetics greater control over their condition.
- Obesity. Dietary fiber makes a person feel full more rapidly. It can thus help a person lose weight by making the appetite easier to control.
- Colon and colorectal cancer. Insoluble fiber in the diet speeds up the movement of the stools through the gastrointestinal tract. The faster that food and its byproducts travel through the digestive tract, the less time there is for potential cancer-causing substances to work on the food. Diets that are high in insoluble fiber help to prevent the accumulation of toxic substances that cause cancer of the colon.
- Breast cancer. A high dietary consumption of fats is associated with an increased risk of breast cancer. Because fiber reduces fat absorption in the digestive tract, it may prevent breast cancer. In 2003, a study confirmed these findings and showed that women who consumed more fiber and vitamin E also had a lower risk of developing benign breast disease, a condition that can lead to breast cancer.
- Prostate cancer. Though research is still relatively new, Dr. Dean Ornish presented new data in April 2002 in a study that showed how a high-fiber vegan diet could slow or even stop prostate cancer for men in early stages of the disease. Men who submitted to an extremely lowfat vegan diet consisting of fruits, vegetables, whole grains, beans and soy products instead of dairy, and who gave up alcohol and agreed to exercise three hours a week, relax and meditate one hour a day showed improvements in markers for prostate cancer indicators. Patients should not try this regimen unless they first discuss it with their doctors. In addition, it should complement other physician–ordered treatments.
The American Dietetic Association recommends eating 25–35 g of fiber daily. A person can meet this fiber requirement by consuming two to three servings of fruits and three to five servings of vegetables every day.
To increase fiber intake, a person should eat more of the following high-fiber foods: whole grains, beans, fruits (preferably with skins on), roots and leafy vegetables, broccoli or carrots. As an added bonus, he or she will also receive other health benefits provided by the vitamins, minerals, antioxidants and cancer-fighting phytochemicals in these foods.
For the greatest benefit to health, people should have both soluble and insoluble fiber in their diet, preferably in a 50:50 ratio. The following foods are good sources of insoluble fiber:
- wheat bran
- whole wheat products
- cereals made from bran or shredded wheat
- crunchy vegetables
- whole-wheat pasta
- rye flour
Good sources of soluble fiber include:
- oat bran
- citrus fruits
- dried beans
- rye flour
- raw cabbage
High-fiber therapy must be part of a balanced diet that includes adequate water intake and also provides the proper amounts of essential vitamins and minerals, including calcium, iron and zinc.
Some side effects such as loose bowel movements, excessive gas, or occasional stomach pain have been reported from high-fiber diets. However, a 2002 report told of a study that followed more than 1,000 women on varying amounts of fiber intake. Those with higher dietary fiber consumption did not report expected symptoms of bloating, gas and stomach upset, so most people can enjoy the benefits of fiber with minimal side effects.
Research and general acceptance
As a result of the large volume of scientific evidence supporting the use of fiber in disease prevention and treatment, high-fiber diet treatments have been accepted and advocated by practitioners of alternative and conventional medicine alike.
High-fiber diets have been endorsed by the American Heart Association, the American Dietetic Association, the National Cancer Institute, the National Research Council, and the United States Department of Health and Human Services.