Fiber is a type of complex carbohydrate that is essential for normal digestion. Even though fiber is a carbohydrate, it does not break down to provide energy in the same manner as starch and sugar carbohydrates. Fiber, which comes solely from plant-based foods, generally fits into either one of two categories: soluble or insoluble. Most high-fiber foods provide both types of fiber, but have higher concentrations of one type over the other. For example, apples are rich in soluble fiber, but if you eat the skin, you also add insoluble fiber to your diet.
Soluble fiber absorbs fluid in your intestines and creates a thick slow-moving sludge. This substance slows down digestion, which gives vitamins and minerals time to absorb through intestinal walls. Without adequate amounts of soluble fiber, these nutrients may pass through your gut and escape through your stool, without being absorbed. Soluble fiber comes from oatmeal, nuts, seeds, beans and the soft inside part of fruits.
Soluble Fiber Health Benefits
In a 2012 study at the Children's Hospital Oakland Research Institute, researchers evaluated the benefits of increasing fiber intake and published their findings in the "Federation of American Societies for Experimental Biology Journal." Research participants consumed a high-fiber, low-calorie fruit bar two times per day. The bar was rich in beta-glucan, a type of soluble fiber. At the end of the two-week study, research participants had an average of 6 percent higher blood concentrations of high-density lipoprotein, or HDL cholesterol. This is the good cholesterol that helps stabilize total cholesterol levels and rids your body of harmful low-density lipoprotein, or LDL cholesterol. Getting more soluble fiber in your diet by eating more fresh fruits may help improve your cholesterol levels.
Insoluble fiber acts differently than soluble fiber by staying intact and speeding up digestion. This type of fiber acts like a broom and sweeps through your intestines creating soft bulky stools. Insoluble fiber is the tough fibrous part of plants that is difficult to chew and passes intact through your body. For example, the skin of corn kernels or strands from celery often come out in large pieces in your stool. Your body lacks the enzymes it needs to break down these tough fibrous compounds. Insoluble fiber comes primarily from vegetables, whole-grain foods, brown rice and barley.
Insoluble Fiber Health Benefits
In 1998, researchers at Harvard Medical School and Brigham and Women's Hospital looked into health benefits of cellulose, an insoluble fiber. Cellulose is the primary component of cell walls and is the rigid structure that makes plants difficult to chew. Researchers evaluated the effect of insoluble cellulose fiber in healthy men. Their findings, published in "The Journal of Nutrition," determined that a diet high in fiber, particularly insoluble cellulose fiber, lessens your risk of diverticular disease. This condition causes pouches to form in your colon where food gets stuck. Diverticular disease can lead to inflammation and complications in your intestine when you do not have regular bowel movements. Insoluble fiber keeps you regular and relieves constipation, reducing your risk of diverticular disorders by ridding your body of waste.
You need 14 grams of fiber in your diet for every 1,000 calories you consume, according to the Dietary Guidelines for Americans 2010. If you typically consume around 2,000 calories, you need 28 grams of total dietary fiber. Eating fresh fruits and vegetables, and opting for whole grains over refined white grains, helps you get both soluble and insoluble fiber in your diet.
- U.S. Department of Agriculture, U.S. Department of Health and Human Services: Dietary Guidelines for Americans 2010
- Centers for Disease Control and Prevention: Carbohydrates
- Federation of American Societies for Experimental Biology Journal: A Nutrient-Dense, High-Fiber, Fruit-Based Supplement Bar Increases HDL Cholesterol, Particularly Large HDL, Lowers Homocysteine, and Raises Glutathione in a 2-wk Trial
- The Journal of Nutrition: A Prospective Study of Dietary Fiber Types and Symptomatic Diverticular Disease in Men
- Whole grain toast served with butter. image by William Berry from Fotolia.com