Dietary fiber, also known as roughage or bulk, includes all parts of plant foods that your body cannot digest or absorb, unlike other food components such as fats, proteins or carbohydrates. Yet it is an important part of a healthy diet. It aids in controlling your weight by adding bulk to your diet and making you feel full faster.
Dietary fiber passes relatively intact through your stomach, small intestine, and colon and out of your body. Fiber is commonly classified into the following two categories: those that do not dissolve in water (insoluble fiber); and those that do (soluble fiber).
Insoluble and soluble fiber
Insoluble fiber (that does not dissolve in water) benefits those who struggle with constipation or irregular stools, as it promotes the movement of material through your digestive system and increases stool bulk. Insoluble fiber is found in whole-wheat flour, wheat bran, nuts, and many vegetables.
Soluble fiber (that can dissolve in water) helps lower blood cholesterol and glucose levels as it dissolves in water to form a gel-like material. Soluble fiber is found in oats, carrots, peas, citrus, beans, apples, fruits, barley, and psyllium.
The American Dietetic Association (ADA) recommends 20 to 35 grams of fiber per day for both men and women. However, an online fiber calculator is available which helps calculate the required intake of fiber depending on your age, height, gender, and frame size. Eat a wide variety of high-fiber foods to receive the greatest health benefits. The big five benefits of dietary fiber include:
- a decrease in the risk of developing some cancers
- an improvement in gastrointestinal health
- a decrease in high blood pressure and other coronary heart disease risk factors
- an improvement in glucose tolerance and insulin response
- weight management
Health benefits of fiber
Consumption of high fiber diet plays a vital role in disease prevention, disease treatment, and biological functions.
High fiber intake can help prevent the following diseases:
- Cardiovascular disease: Consumption of fiber rich foods is associated with significant reduction in coronary heart disease (CHD). High fiber cereal and fruits are associated with decreased CHD deaths. Fiber-rich diets may also help in lowering the blood pressure, another important risk factor for cardiovascular disease. Higher consumption of dietary fiber may lower the levels of C-reactive protein, a biomarker of inflammation which is strongly associated with the risk of cardiovascular events, such as myocardial infarction and stroke.
- Type 2 diabetes mellitus: Soluble fiber can slow the absorption of sugar which helps improve blood sugar levels in people with type 2 diabetes. An insoluble fiber (particularly cereal fiber from whole grains) intake has been associated with a reduced risk of developing type 2 diabetes.
- Cancers: Substantiation that dietary fiber reduces the risk of colo rectal cancer is controversial. However, European Prospective Investigation into Cancer and Nutrition (EPIC) study found that dietary fiber from foods was protective against colon cancer development. So, concerned individuals adopt a colon cancer screening regimen to prevent colorectal cancer. Regular testing and removal of colon polyps can prevent colon cancer. Clinical evidence suggests that high intake of fiber foods (in conjunction with lifestyle changes and conventional medication) may help protect against certain types of cancer such as prostate, breast, and lining of the uterus. However, further research is required.
- Diverticular disease: Diverticulosis is a relatively common condition that is characterized by the formation of small pouches (diverticula) in the colon. High fiber intakes are associated with decreased risk of diverticulosis.
- Weight control: There is some evidence that higher fiber intakes can help to prevent weight gain or promote weight loss by extending the feeling of fullness after a meal (satiety)
- Hemorrhoids (piles): A high fiber diet may lower the risk of developing hemorrhoids (piles) by maintaining the bowel integrity and health. Fiber intake also aids in increasing the weight and size of the stool and also softens it, thereby making it easier to pass, decreasing the chance of constipation.
Consumption of fiber can also help treat the following diseases:
- Diabetes mellitus: A high intake of fiber improves markers of glycemic control, particularly postprandial glucose levels, and serum lipid profiles in people who have type 1 or type 2 diabetes mellitus.
- Irritable bowel syndrome: IBS is a functional disorder of the intestines, characterized by episodes of abdominal pain or discomfort associated with a change in bowel movements, such as constipation or diarrhea. Fiber intake may provide relief.
A high fiber intake also aids the following biological functions:
- Lowering postprandial glycemia: The addition of dietary fiber to a carbohydrate-containing meal has been found to result in significant improvements in blood glucose and insulin responses.
- Lowering serum cholesterol: A high intake of dietary fibers, particularly from legumes (dry beans, peas, and lentils) and oat products decrease the serum total and LDL cholesterol.
Concerns with dietary fiber
Anything more than the recommended daily allowance (20 to 35 g/day) of fiber intake can create problems. An increase in fiber leads to gas problems, diarrhea and dehydration, weight gain due to retention of water, abdominal bloating, stomach pain, and flatulence. Therefore, it should be introduced slowly to the diet.
Disclaimer: The information contained in this article is for educational purposes only; it should not be used for diagnosis or to guide treatment without the opinion of a health professional. Any reader who is concerned about his/her health should contact a licensed medical professional.
Mayo Clinic, “Facts of Dietary Fiber” Accessed March 05, 2011