Dietary Fiber Introduction

Dietary fiber is a class of carbohydrate compounds that are commonly found in fruits and vegetables. There are no forms of dietary fiber found in animal derived food sources. In general, dietary fibers can be divided into two main classifications;

Soluble fiber and Insoluble fiber.

  • Soluble fiber: capable of absorbing water and forming a gel-like material in the intestinal tract. Can help with the removal of waste products such as hormones and drugs.
  • Insoluble fiber: important in maintaining proper bowel function by promoting normal mass movements within the bowel. Majority of fruits and vegetables contain both soluble and insoluble fiber; both are necessary for health.

Dietary Fiber Uses

Irritable Bowel Syndrome (IBS):

Irritable Bowel Syndrome is a digestive condition that affects many people and can cause result in a diverse range of symptoms, including gas, constipation, diarrhea, and abdominal discomfort. IBS is considered a diagnosis of exclusion that is arrived at only after all other possibilities have been ruled out. High-fiber diets and the supplementation of fiber products has been shown to have beneficial effects for IBS sufferers; as evaluated by improvement in bowel habits, flatulence, and abdominal pain. [1, 2]

Cholesterol Control:

Cholesterol is a substance that occurs naturally in the human body as well as in any animal based foods. Cholesterol is an vital nutrient. It is used to maintain the fluidity of our cellular membranes as well as in the manufacturing of steroid-based hormones, which are essential for normal growth and sexual function. Excessive levels of cholesterol, due to ether high intake or high production of cholesterol, can cause serious problems within the body. There are two main categories of cholesterol; HDL (High density Lipoprotein, or “good”) cholesterol, and LDL (Low density Lipoprotein,”bad”) cholesterol. The problems that result from excess LDL cholesterol primarily affect the cardiovascular system; contributing to several pathologies, including heart attack and elevated blood pressure.

Numerous studies support the use of fiber (particularly soluble fiber) in the treatment of hypercholesterolema due to both genetic and dietary causes. In general, increases in dietary fiber are associated with small, but often reliable, decreases in serum LDL (Low Density Lipoprotein;”Bad”) cholesterol. Positive changes in cholesterol have also been noted in many studies conducted on dietary fiber ingestion, where cholesterol levels weren’t considered within the parameters specifically being studied. Due to the reliable nature of the beneficial effects of fiber on serum cholesterol and the potential side effects of commonly used ant-cholesterol medications, dietary fiber as a therapeutic intervention in high cholesterol is definitely worthy of consideration. [3-8]

Weight Reduction:

One of the primary causes for obesity is excessive intake of energy-rich foods without a corresponding increase in energy consuming physical activity. One of the functions of dietary fiber is to assist in creating feelings of satiety to prevent one from overeating. Increased fiber intake can be equally beneficial by cleansing the body, mainly within the parameters of the elimination of fats and toxins from the body. Increased fiber consumption has been demonstrated to be associated with a decrease in energy intake (10%), as well as a concomitant weight loss over a 4 month period; this effect was increased in individuals that where considered obese. [9]

Cancer prevention:

Cancer is a widely feared illness involving damage to cellular DNA. This damage results in an uncontrollable mutation of cells that causes widespread bodily damage, and in some cases, death. While no specific dietary interventions have be proven to effectively treat or reverse cancer, there is evidence that suggests that there are dietary interventions that are associated with a reduced incidence and recurrence of specific cancers. Positive benefits with regards to cancer are associated with diets high in fiber and low in fat, as well as with fiber supplementation. [10-13]

Improve Bowel Function:

One of the primary functions of fiber in the body is to ensure that there is adequate bulk in the bowel to allow for proper and timely elimination of wastes. In many medical settings, such as convalescent homes where patents have limited diets low in fiber, laxatives are used to ensure that the patients are able to defecate regularly. The use of laxatives can be habit forming with patients often become physically dependent on the drugs to produce normal active bowel function. As many pharmaceutical laxatives are irritating stimulants, they may cause additional problems for patients using these medicines over the long-term. There are many approaches that can be utilized to prevent constipation in a managed care setting. These include; a timely elimination schedule, adequate fluid intake, regular exercise, and high intakes of dietary fiber. [14]

Blood Sugar regulation:

Type I Diabetes often results in high levels of blood sugar, subsequently, many tissues become damaged and lose much of their ability to function properly. Diabetics commonly have high blood lipid concentrations, which can contribute to various negative health conditions including cardiovascular disease. A high fiber diet consumed for as little as six weeks may provide for significant reductions in plasma glucose concentrations and urinary glucose secretion. High fiber intake has also shown to be beneficial in other conditions where there is a resistance to the natural production of insulin; as in cases such as Diabetes Type II and Syndrome X. High fiber diets are also effective in the prevention of various blood sugar control syndromes. [15-17]

Hormonal Regulation:

The bowels serve as one of the primary avenues for elimination of unwanted substances from the body. Among substances that must be successfully removed from the body are naturally occurring hormones and their metabolites. When excessive hormones remain in the bowel they can be reabsorbed and cause individual specific symptoms, depending on the unique characteristics of the hormone in question. For example, a common cause of menstrual and premenstrual symptoms is the presence of excessive levels of estrogen and its metabolites. Low-fat and High-fiber diets have been shown to decrease the serum concentrations of various hormones, such as estrogen and thus could have positive impacts on pathologies that are sensitive to these hormones (e.g PMS). One study demonstrated that serum estrone sulfate concentrations could be decreased by as much as 25% by the use of a high-fiber, low-fat diet. [18]

Dietary Fiber Dosages

The typical Western diet contains less than 15 grams of fiber per day. However this is considered inadequate, as recommendations for the normal dietary intake of fiber range from 25 - 30 grams daily. For the treatment of specific conditions (e.g. high cholesterol) directions from a qualified health care professional should be followed, due to individual variations of fiber tolerance.

Dietary Fiber Toxicities and Deficiencies

Fiber is generally safe, though persons suffering from certain underlying medical conditions, like Scleroderma, should consult their physician before increasing intakes of fiber. Certain minerals and prescription medications can also interact with fiber and/or have their absorption impaired by this class of carbohydrates.


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