Why is Fiber Important and How is it Beneficial to Your Health?
A High Fiber Diet Might Lower Cholesterol and Prevent Heart Disease
Dietary fiber seems to be an important part of human health. We can analyze ancestral diets to determine what our bodies were designed to digest, and use this to postulate what we should and should not be eating. Fiber is an indigestible carbohydrate, but it appears that it is important in maintaining the short digestive cycles that our hominid ancestors exhibited. While large brained primates did avoid fiber to some degree, they did consume a much higher amount of this nutrient compared to the current American diet. The U.S. Senate Select Committee recommends 30-60 grams of dietary fiber per day whereas the average American in 1976 consumed 19.7 grams. This is significantly less than the late Paleolithic diet which consisted of 45.7 grams of fiber per day. This is important from an evolutionary perspective because ancestral food pressures have determined the structure of our modern digestive tract. Natural selection has given preference to large brains and short colons that pass food very quickly. This short gut residence time is largely facilitated by adequate amounts of fiber. Less fiber causes waste material to reside in the colon for long periods of time, potentially causing digestive problems and disease. Therefore, analyzing ancestral diets may help us solve contemporary health problems.
So where is fiber found in the environment? Consisting of indigestible plant carbohydrates, such as cellulose, lignin, and pectin, fiber is found in fruits, vegetables, grains and beans. Fiber is either soluble or insoluble. Insoluble fiber includes the woody or structural parts of plants and does not dissolve in water. Examples are the skins of fruits and vegetables and the bran coating around wheat and corn kernels. These foods speed up the passage of material through the tract and remain largely unchanged throughout the consumption and defection process. Soluble fiber is found in beans, oats, barley, broccoli, prunes, apples, and citrus fruits. This type of fiber dissolves in water and forms a gel, slowing the passage of material through the tract. Soluble fiber may be beneficial in a contemporary setting because of its ability to lower blood cholesterol. Soluble fiber does this by binding to bile salts and prevents their reabsorption. This reduces the amount of bile salts in the liver and causes the liver to use cholesterol to make new bile salts, reducing the amount of cholesterol in the blood.
Incorporating more fiber into the diet has many other contemporary applications. Many diseases that Americans face may be preventable through a high fiber diet, such as heart disease which is characterized by a build up of cholesterol-filled plaque in the coronary arteries. Because a high fiber diet reduces blood cholesterol levels, heart disease incidences may be reduced with elevated levels of dietary fiber. High fiber diets have also been linked to reduced incidences of type II diabetes, diverticular disease, and constipation.
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Pereira MA, O'Reilly E, Augustsson K, et al. “Dietary fiber and risk of coronary heart disease: a pooled analysis of cohort studies.” Arch Intern Med 164 (2004):370-6.
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Van Horn L. Fiber, lipids, and coronary heart disease. “A statement for healthcare professionals from the Nutrition Committee, American Heart Association.” Circulation 95 (1997):2701-4.
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