Did you know there’s more than one type of dietary fiber? Eating a wide range of plant foods will help you meet all your needs.
Fiber is important in your diet and most people don’t eat as much as they should. In addition to eating enough fiber, you also need to eat enough of the different types of fiber. That’s because not all fibers function exactly the same way—different types of fibers have different effects on the body. So, just as you should aim to eat a wide range of foods in order to get a wide array of nutrients, a varied diet helps to provide you with enough of the different types of fibers, too.
Fiber is the structural component of plant foods, so it’s found in vegetables, whole fruits, beans and grains (like corn or brown rice)—there’s no fiber in meats, fish or poultry.
The average American falls far short of meeting the fiber recommendation of 25-30 grams a day. In fact, most of us only eat about 10 grams a day, which means we may be missing out on the health benefits of dietary fiber. Fiber, of course, helps move the digestive process along, but high fiber foods also provide the sensation of fullness, so they help with hunger control. And certain fibers also support the growth of friendly bacteria in your digestive tract.
If you don’t eat as much fiber as you should, it’s best to increase the amount you eat gradually over a few weeks. Adding too much fiber to the diet in a short period of time might lead to abdominal discomfort and gas, so take it slowly to allow your system time to adjust. Also, drink plenty of liquid to allow the fiber to soften and swell.
There are two broad classes of dietary fiber—soluble fibers and insoluble fibers.
Soluble fibers are found in the highest concentration in apples, oranges, carrots, potatoes, oats, barley and beans. Soluble fibers dissolve in water and thicken up. If you’ve ever cooked oatmeal at home, you probably noticed it got thick and gluey as it cooked. That’s because the soluble fiber in the oats dissolved in the liquid.
When these fibers come in contact with the liquid in your stomach, they swell up and thicken, too, which is why they help keep you full. Soluble fiber slows the absorption of glucose (sugar) from the blood stream and it can help to keep blood sugar levels more even throughout the day.
Insoluble fibers also support the health of your digestive system, but in a different way. Insoluble fibers don’t dissolve in water—instead, they simply absorb water in the lower tract, which makes the fiber more bulky. This type of fiber, found in the highest concentrations in vegetables, wheat bran, corn bran, rice bran and most other whole grains, speeds the passage of waste through your digestive system, so it helps to keep you regular.
It’s actually fairly easy to tell the two fibers apart. When you make barley soup or boil potatoes, you can easily see how the liquid thickens up—that’s because barley and potatoes are high in soluble fiber. On the other hand, when you cook brown rice—a whole grain that’s rich in insoluble fiber—it doesn’t get sticky because the fiber doesn’t dissolve. Instead, it simply absorbs water as it cooks, causing the grains to swell up.