Fibers are long polymers of sugars and are classified as carbohydrates. Dietary sources of fiber are primarily obtained from plants, and good sources of dietary fiber are whole grain foods, beans and peas, nuts, vegetables and fruits. The American Dietetic Association, or ADA, reports that there is fair evidence that dietary fiber or fiber obtained from supplements lowers blood pressure, improves lipid profiles and reduces inflammatory markers of cardiovascular disease. Additionally, The Dietary Guidelines Advisory Committee, or DGAC, purports that there is evidence to suggest diets high in fiber are associated with a reduction in the risk for obesity and diabetes, which are primary risk factors for cardiovascular disease.
Fiber Definition
Fiber, in contrast to other carbohydrates, is not broken down in the small intestine to glucose and remains intact. Bacteria in the large intestine break down soluble fiber into nutrients that can be absorbed and used by the body. The remainder of fiber, which is insoluble, is not digested and excreted. The Institute of Medicine, or IOM, states that "dietary fiber consists of nondigestible carbohydrates and lignin that are intrinsic and intact in plants" and functional fiber, also called added fiber "consists of isolated, nondigestible carbohydrates that have beneficial physiological effects in humans."
Recommended Intake
The DGAC reports that most Americans do not consume enough dietary fiber. The IOM states that an adequate Intake of fiber is 14g per 1,000 kilocalories. The American Heart Association recommends a dietary fiber intake of 25g per day. The DGAC also reports that manufacturers of products containing dietary fiber are allowed to call a food a "good source of fiber" if it contains 2.5g per serving and an "excellent source of fiber" if the food contains 5g per serving.
Obesity and Cholesterol
Obesity and high levels of cholesterol are risk factors for heart disease. The ADA concludes that diets high in fiber stimulate the feeling of fullness and are linked to decreased body weight. A study in the March 2009 issue of "The Journal of Nutrition" reports that for each 1g increase in total fiber consumed per day weight gain was decreased by 0.25kg. The American Heart Association notes that diets high in soluble fibers, like that found in peas, beans, oats and fruits, moderately reduce low density lipoproteins, also known as "bad cholesterol" or LDL.
Diabetes
The American Diabetes Association reports that people who have diabetes die from heart disease at rates two to four times higher than those without diabetes. A study reported in the March 2009 "The Journal of Nutrition" found that people who had a high dietary fiber intake had a significantly decreased risk for developing type 2 diabetes.
Heart Disease
A review of several trials in the Jan. 24, 2005, "Archives of Internal Medicine" reports that increased fiber intake reduces hypertension, especially in older hypertensive people. A study in the October 2010 issue of the "American Journal of Clinical Nutrition" reports that three daily portions of whole grain foods significantly decreased blood pressure in middle-aged people and that the reduction in blood pressure could decrease the incidence of cardiovascular disease by greater than 15 percent in this population. The American Heart Association reports that diets high in insoluble fiber, like that found in whole grains, are associated with decreased cardiovascular risk and delayed progression of heart disease in high-risk individuals.
References
- The National Academies Press (Institute of Medicine): Dietary Reference Intakes: Proposed Definition of Dietary Fiber (2001)
- United States Department of Agriculture: Dietary Guidelines for Americans--Carbohydrates
- "The Journal of Nutrition"; Increasing Total Fiber Intake Reduces Risk of Weight and Fat Gains in Women; L.A. Tucker and K.S. Thomas; March 2009
- "Archives of Internal Medicine"; Dietary Fiber and Blood Pressure: A Meta-Analysis of Randomized Placebo-Controlled Trials; M.T. Streppel et al.; January 2005
- "American Journal of Clinical Nutrition"; Effect of Increased Consumption of Whole-Grain Foods on Blood Pressure and Other Cardiovascular Risk Markers in Healthy Middle-Aged Persons: A Randomized Controlled Trial; Paula Tighe et al.; October 2010
