What is dietary fiber?
Dietary fiber, or fiber, is a type of carbohydrate found in plant foods and is made up of many sugar molecules linked together. But unlike other carbohydrates (such as starch), dietary fiber is bound together in such a way that it cannot be readily digested in the small intestine.
There are two types of dietary fiber, and most plant foods contain some of each kind:
- Soluble fiber dissolves in water to form a thick gel-like substance in the stomach. It is broken down by bacteria in the large intestine and provides some calories. Soluble fiber is found in a variety of foods, including: Beans and peas, fruits, nuts and seeds, vegetables.
- Insoluble fiber does not dissolve in water and passes through the gastrointestinal tract relatively intact and, therefore, is not a source of calories. Insoluble fiber is found in a variety of foods, including: fruits, nuts and seeds, vegetables, wheat bran, whole grain foods
The benefits of fiber
Soluble fiber can interfere with the absorption of dietary fat and cholesterol. This, in turn, can help lower low-density lipoprotein (LDL or “bad”) cholesterol levels in the blood. Soluble fiber also slows digestion and the rate at which carbohydrates and other nutrients are absorbed into the bloodstream. This can help control the level of blood glucose (often referred to as blood sugar) by preventing rapid rises in blood glucose following a meal.
Insoluble fiber provides “bulk” for stool formation and speeds up the movement of food and waste through the digestive system, which can help prevent constipation.
Both soluble and insoluble fiber make you feel full, which may help you eat less and stay satisfied longer. Diets higher in dietary fiber promote intestinal regularity and can reduce the risk of developing cardiovascular disease.
Unfortunately, many people do not get the recommended amount of dietary fiber. Dietary fiber is considered a “nutrient of public health concern” because low intakes are associated with potential health risks. The U.S. National Library of Medicine has a topic discussing the benefits about fiber. Taking dietary fiber supplement is a viable option.
How much fiber do I need?
Use the Nutrition Facts Label as your tool for increasing consumption of dietary fiber. The Nutrition Facts Label on food and beverage packages shows the amount in grams (g) and the Percent Daily Value (%DV) of dietary fiber in one serving of the food.
Food manufacturers may voluntarily list the amount in grams (g) per serving of soluble fiber and insoluble fiber on the Nutrition Facts Label (under Dietary Fiber), but they are required to list soluble fiber and/or insoluble fiber if a statement is made on the package labeling about their health effects or the amount (for example, “high” or “low”) contained in the food.
The Daily Value for fiber is 25 g per day. This is based on a 2,000 calorie diet — your Daily Value may be higher or lower depending on your calorie needs. The goal is to get 100% of the Daily Value for dietary fiber on most days. And remember:
- 5% DV or less of dietary fiber per serving is low
- 20% DV or more of dietary fiber per serving is high
Dietary fiber supplements are available in many forms and allow people to increase the amount of fiber in their diets if they aren’t eating or getting enough from food.
Short-term relief from constipation and bowel irregularity are common reasons people use fiber supplements. Dietary fiber supplements are also used in weight management because it helps people feel fuller longer.
Whether you increase your fiber intake using a supplement or by eating a higher fiber diet, be sure to increase your fluid intake as you increase your fiber. Fluid is required to help push fiber through the digestive tract, and too little water with more fiber could worsen constipation.
Prebiotics: the fiber that feed the friendly bacteria
Prebiotics are the type of dietary fiber supplements that feed the friendly bacteria in your gut. This helps the gut bacteria produce nutrients for your colon cells and leads to a healthier digestive system. Some of these nutrients include short-chain fatty acids like butyrate, acetate and propionate. These fatty acids can also be absorbed into the bloodstream and improve metabolic health.
Many foods, such as vegetables, fruits and legumes, naturally contain prebiotics. Some of the fiber content of these foods may be altered during cooking, so try to consume them raw rather than cooked.
However, prebiotics should not be confused with probiotics. Probiotics are beneficial bacteria, while prebiotics are food for these bacteria. You don’t need to take a prebiotic for probiotics to work, but taking them might make your probiotics more effective.
The use of prebiotics and probiotics together is called microbiome therapy.
Some research indicates that prebiotics and probiotics are effective for treating diarrhea, irritable bowel syndrome, allergic disorders, and even the common cold. Prebiotics and probiotics have been suggested as treatments for obesity. They are being explored as a way to prevent the spread of cancer.