Everybody talks about fiber, but what is it exactly? How do you get fiber in your diet? What are the different kinds of fiber? More importantly, what are the benefits of a diet rich in fiber?
Fiber is the term used to describe carbohydrates that cannot be digested and therefore cannot be absorbed by the human intestinal tract. Fiber in itself has no calories. Fiber is not a single food or substance. Fiber is found in all plants that we consume as food. Examples of food that contain fiber are fruits, vegetables, grains, and legumes. There are two different kinds of fiber-- one called soluble fiber because of its ability to dissolve in water and another one called insoluble fiber because it does not dissolve in water. Each kind of fiber has different effects on our bodies, and will protect us against different kinds of diseases.
When we take insoluble fiber like the one present in cellulose our stools become larger and softer, because this kind of fiber "bulks up" waste products and moves them through the colon faster, preventing constipation and possibly colon cancer. Furthermore this type of fiber takes up space in the stomach, making us feel full; therefore food intake is less, making it an ideal part of a weight loss program.
Soluble fibers, such as gum and pectin dissolve in water and are very sticky. These kinds of fiber can help control cholesterol by removing the bile acids that digest fat in our body. If there is no fat to absorb, then there is no fat available to make cholesterol. Another benefit of soluble fibers is that they may help regulate blood sugar by attaching to the gut's lining and delaying the emptying of the stomach. When our stomach takes longer to empty, the absorption of sugars in the intestine decreases, and so does the amount of insulin secreted.
Examples of insoluble fiber are: Fruits, vegetables, dried beans, wheat bran, seeds, popcorn, brown rice, and whole grain products such as breads, cereals, and pasta.
Sources of soluble fiber are: Fruits such as apples, oranges, pears, peaches, and grapes; vegetables, seeds, oat bran, dried beans, oatmeal, barley and rye.
The current recommendation for daily fiber is 20-35 grams/day. The average American consumes about half of the recommended amount of fiber. Children over the age of 2 should consume an amount equal to or greater than their age plus 5 grams per day.
When you first start to increase the amount of fiber in your diet you might increase the production of intestinal gas, and therefore you could feel bloated and develop diarrhea. One way to avoid these side effects is to increase the amount of fiber gradually over a period of three weeks.
Some tips for increasing fiber intake:
- Choose fresh fruit or vegetables rather than juice.
- Eat the skin and membranes of cleaned fruits and vegetables
- Replace white rice, bread, and pasta with brown rice and whole-grain products.
- Choose whole-grain cereals for breakfast.
- Snack on raw vegetables instead of chips, crackers, or chocolate bars.
- Substitute legumes for meat two to three times per week
- Experiment with international dishes (such as Indian or Middle Eastern) that use whole grains and legumes as part of the main meal (as in Indian dahls) or in salads (for example, tabbouleh).
- An increase in fiber should be accompanied by an increase in water.
- Eat less processed foods and more fresh ones.
- It is better to get fiber from foods rather than fiber supplements as foods are more nutritious
Marcela Nur, MD