Fiber is a special type of complex carbohydrate not digested and not absorbed in the small intestine. Fiber is sometimes called roughage or non-starchy polysaccharides.
Some examples of fiber include cellulose, hemicellulose, pectin, fructans, beta-glucans, and a variety of gums, mucilage, and algal polysaccharides. Fibers are usually components of plant cell walls and intracellular structures. Although largely indigestible, fiber plays an important role in the diet. Fiber helps promote efficient intestinal functioning and aids in the absorption of sugars and other nutrients into the bloodstream.
There are two types of dietary fiber, and most plant foods contain some of each kind:
1. Soluble fiber, found in certain foods, serves several important functions in the body:
- Promotes Digestive Health: Soluble fiber absorbs water in the digestive tract, forming a gel-like substance that softens stools and promotes regular bowel movements. This can help prevent constipation and promote overall digestive health.
- Lowers Cholesterol: Soluble fiber binds to cholesterol particles in the digestive tract, helping to lower levels of LDL cholesterol (the “bad” cholesterol) in the blood. By reducing cholesterol absorption, soluble fiber can contribute to a lower risk of heart disease.
- Regulates Blood Sugar Levels: Soluble fiber slows down the absorption of sugar in the bloodstream, which helps prevent spikes in blood sugar levels after meals. This can be particularly beneficial for individuals with diabetes or those at risk of developing diabetes.
- Feeds Beneficial Gut Bacteria: Certain types of soluble fiber are fermented by bacteria in the colon, producing short-chain fatty acids like butyrate. These fatty acids provide energy to the cells lining the colon and support the growth of beneficial bacteria, contributing to a healthy gut microbiome.
Some examples of foods rich in soluble fiber include oats, barley, legumes (such as beans and lentils), fruits (such as apples, oranges, and berries), vegetables (such as carrots and Brussels sprouts), and psyllium husk. Incorporating these foods into your diet can help you enjoy the many benefits of soluble fiber.
2. Insoluble fiber: Insoluble fiber does not dissolve in water and passes through the gastrointestinal tract relatively intact and is not a source of calories.
- Promotes Regular Bowel Movements: Insoluble fiber adds bulk to stools, which helps move waste through the digestive system more efficiently. By speeding up transit time in the digestive tract, insoluble fiber can help prevent constipation and promote regularity.
- Supports Digestive Health: Insoluble fiber can help prevent diverticulosis and diverticulitis by reducing pressure in the colon and preventing the formation of diverticula (small pouches in the colon wall). Additionally, it may lower the risk of developing hemorrhoids by keeping stools soft and preventing straining during bowel movements.
- Provides Intestinal Cleansing: Insoluble fiber acts as a natural intestinal scrub brush, helping to sweep waste and toxins out of the digestive tract. By keeping the colon clean and preventing the buildup of waste materials, insoluble fiber supports overall colon health.
- May Reduce Risk of Colon Cancer: Some research suggests that a high-fiber diet, including insoluble fiber, may help reduce the risk of colon cancer. Insoluble fiber promotes regular bowel movements, which may help prevent harmful substances from lingering in the colon and potentially damaging the intestinal lining.
Examples of foods rich in insoluble fiber include whole grains (such as wheat bran, whole wheat bread, and brown rice), nuts and seeds, vegetables (such as broccoli, cauliflower, and celery), and the skins of fruits and vegetables. Incorporating these foods into your diet can help you enjoy the many benefits of insoluble fiber and support overall digestive health.
Aids in Weight Management: Soluble fiber and Insoluble fiber adds bulk to meals without adding calories, which can promote feelings of fullness and satiety, which can reduce appetite and overall calorie intake. By promoting a sense of fullness, soluble and insoluble fiber can aid in weight management and contribute to healthy weight loss or maintenance.
Both fiber and digestible carbohydrates contribute to helpful gut bacteria. The gut microbiome depends on nourishment just like any other ecosystem. Prebiotic and probiotic supplements and foods provide nutrition to support friendly, so-called good bacteria in the gut, which can aid in digestive health and proper functioning. Research suggests that gut bacteria particularly prefer fructans and cellulose.
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