Dietary fiber, or roughage, is a carbohydrate found in the structural material of plants including the leaves, stems and roots. Dietary fiber is present in all plant foods such as fruits, vegetables, whole grains, legumes, nuts and seeds. Fiber is indigestible and stays intact until it nears the end of the digestive system. Fiber has a low glycemic index, helping to avoid large insulin spikes after a meal and having a beneficial effect on insulin sensitivity.
There are two basic types of fiber and each has its own functions. Both types of fiber are important for health, digestion and prevention of health conditions such as heart disease, diabetes and obesity.
- Soluble fiber – This type of fiber dissolves in water to form a gel-like substance in your digestive tract. Soluble fibers slow down the movement of food through the digestive system, delaying the emptying of stomach contents, and keeping that feeling of fullness for longer periods of time. Soluble fiber plays an important role in lowering LDL cholesterol by interfering with the absorption of dietary cholesterol.
- Insoluble fiber – Sometimes called cellulose, this fiber has a thick, rough texture that does not dissolve in water. Insoluble fibers absorb water as they move through the digestive tract and tend to accelerate the movement of food and waste. Insoluble fiber is considered gut healthy as it tends to have a laxative effect, helping to keep bowels regular.
Fiber is an essential part of the diet. With the increase of processed and refined foods, the American diet has seen a decrease in the amount of fiber consumed. On a daily basis, the majority of Americans currently get about half of the recommended amounts of fiber. A general recommendation for female adults is 21-25 grams of dietary fiber per day. For adult males, 30- 38 grams of fiber daily. Dietary fiber is beneficial because it:
- Helps to lower blood cholesterol and triglyceride levels.
- Lowers the risk of colon cancer, heart disease, and digestive conditions such as diverticulitis.
- Improves blood sugar levels in type 2 diabetics and aids in prevention.
- Helps control weight by adding bulk to the diet.
- Keeps the digestive system healthy and regulates bowel action.
- Speeds up the transit time through the intestines to aid in elimination of waste and toxins.
Soluble and insoluble fiber can be found in different foods and also in different parts of the same food. Insoluble fiber tends to be found in the peels and husks of plant foods and soluble fiber in the fleshy interior. To ensure that you are getting enough fiber and to get a healthful balance of both types of fiber, look to whole foods and grains. Fiber-rich foods tend to improve the overall quality of your diet as they are rich in vitamins, minerals and disease-fighting phytochemicals. Because the body doesn’t break down fiber, you don’t get an appreciable amount of calories, which explains why you can eat a large salad or a lot of vegetables and still eat very few calories.
Sources of soluble fiber include oatmeal, oat bran, apples, oranges, strawberries, raspberries, beans and legumes, fruits, potatoes and root vegetables.
Sources of insoluble fiber include corn, brown rice, bran, whole grains, nuts and seeds, vegetables with fibrous skin, and fruit peels.
Balanced sources of both soluble and insoluble fiber could include, sunflower, sesame, pumpkin and flax seeds.
Food labels list the amount of fiber per serving but don’t distinguish between the fiber types. It pays to read labels when looking to increase your fiber intake as labels can claim a “good source of fiber” if it contains 2.5 grams, and an “excellent source of fiber” if it contains 5 grams. Increase fiber-rich foods gradually to give your digestive system time to adapt. Be sure to consume plenty of water and stay well hydrated. It’s easy to add fiber to your diet when you think in terms of whole foods – a piece of fruit instead of juice, a high-fiber breakfast cereal, whole grain bread as opposed to refined white bread, and plenty of fresh fruits and vegetables.