The Facts About Fiber

By Dena McDowell, MS, RD, CD

You may have heard that eating a high-fiber diet may help prevent disease, but some of the news about the potential impact of fiber on your health might also have you confused. Can it actually help prevent cancer? What about high blood pressure? If I eat more fiber, will I lose weight? Discovering the important role that fiber plays in your diet is important, and knowing what foods are rich in fiber and how to increase it in your diet can help your overall health. So what is fiber, and why do we need it?

Fiber Facts

Commonly known as bulk or roughage, fiber is the part of plant foods that our bodies cannot digest. Fiber promotes wavelike contractions that move food through the gastrointestinal system. Increasing fiber intake expands the walls of the colon and makes it easier to pass waste through the body. There are two types of dietary fiber: soluble and insoluble, each with its own function. Soluble fiber dissolves in water, forming gelatinous substances in the colon and helping delay stomach emptying. Consuming this type of fiber can help reduce cholesterol as well as aid in controlling blood sugars, which is important for people with diabetes. Good food sources of soluble fiber include oatmeal, oat bran, fruit, barley, and legumes. Insoluble fiber—found in foods like dark green leafy vegetables, whole-wheat products, and the skins of fruit—cannot dissolve in water and cannot be absorbed by the intestinal tract. It adds bulk and helps prevent constipation.

There are many health benefits to eating foods rich in fiber. Fiber can help control diverticular disease, irritable bowel syndrome, hemorrhoids, gallstones, hiatal hernia, high blood pressure, and stroke and can also promote weight loss. In recent years questions have been raised about the connection between fiber intake and cancer risk, as various studies have sought to determine if higher levels of dietary fiber can decrease cancer risk. Although some individual studies have reported a benefit, large combined analyses suggest that fiber intake may have little effect on cancer risk. [1] Though the connection to cancer risk has not been established, the other known benefits of fiber make it an important part of a balanced diet.

Need Help Roughing It? Read This!

The American Dietetic Association recommends that adults consume between 25 and 35 g (grams) of fiber each day. For most Americans—who consume between 10 and 15 g of fiber a day on average—this may sound like a lot. But eating a varied, well-balanced diet can make it easy to reach this goal. Eating two to three servings of fruit, three to five servings of vegetables, and two to three servings of whole-grain starches a day, as well as substituting legumes (beans or lentils) for meat a few times a week, will put you right on the mark. In addition, by filling your plate two-thirds full of fruits, vegetables, and whole grains and leaving the remaining third for the meat or a protein alternative such fish, beans, or tofu, you can further help increase fiber and reduce calorie intake.

Our ancestors’ diets were based on fruits, vegetables, and whole grains. As time progressed, the American diet moved away from whole foods and focused more on technology-based, or processed, foods. These processed foods have become staples in our diet, which has also affected our fiber intake because the more processed a food is, the lower the fiber content. Sticking with a diet based on whole, fresh foods will automatically guide you toward food choices that are higher in fiber. In addition, as you make healthy, fiber-filled choices, keep these facts in mind:

  • Crunchy does not always mean high in fiber; celery, for example, is crunchy but contains less than 1 g of fiber.
  • Check labels closely. All wheat bread, for instance, may not be high in fiber; look for labels that promise whole- wheat bread to be sure you get the most fiber for your money.

If you’re doing your best to fill your diet with good fiber choices and are still having trouble getting enough fiber, a supplement may be beneficial. These products add bulk and help the digestive tract perform naturally. It should be noted, however, that fiber supplements such as Metamucil,® Citrucel,® FiberCon,® and Benefiber® are missing the vitamins, minerals, antioxidants, and phytochemicals that work together to prevent disease. Also, consult your doctor before using these products, as they can allow the colon to rest, which can lead to greater constipation and dependence.

The Final Word

Though adding fiber to your diet might mean making a few changes to your meal plans, the benefits to your overall health are worth the effort. To help your body transition easily, remember these tips as you add more fiber-rich foods to your diet:

  • Add fiber gradually to reduce excess gas, bloating, and cramping that can sometimes occur.
  • Remember to drink plenty of water to prevent constipation.
  • Avoid eating gas-forming vegetables such as broccoli, cabbage, and cauliflower at the same time as legumes. To reduce the gassiness of legumes, rinse canned beans or drain the liquid from soaked beans before cooking with them.
  • Remember to slow down as you eat and to chew your food well to aid digestion.

With these tips in mind, set a goal to assess your current fiber intake and increase slowly to the goal of 25 to 30 g a day. Your body will thank you for it!

Black Bean Burgers

12 oz. can of black beans, rinsed

1 cup whole-wheat breadcrumbs

1 large egg

½ cup diced red onion

½ cup fresh or frozen corn

1 teaspoon minced garlic

½ teaspoon salt

1 teaspoon cumin

1 teaspoon chili powder

oil for frying

In large mixing bowl, mash together beans, breadcrumbs, and egg. Add onion, corn, garlic, salt, cumin, and chili power. Mix well and form into six balls of equal size. Flatten to ½-inch thickness. Heat oil in frying pan. Add burgers and cook each side for 2 to 3 minutes. Serve on whole-grain bun with lettuce, tomato, and condiments of your choice.

Nutritional analysis per burger (without bun and condiments):

150 calories, 25 g carbohydrates, 4 g fiber, 7 g protein, 2 g fat, 31 mg (milligrams) cholesterol

Fiber Content of Common Foods

Food Amount Fiber (grams)
Beans, cooked ½ cup 8
Lentils, cooked ½ cup 8
Bran flakes 1 cup 7
Shredded wheat 1 cup 6
Acorn squash, baked ½ cup 5
Baked potato with skin 1 medium 4
Hummus ¼ cup 4
Bulgur, cooked ½ cup 4
Broccoli, cooked ½ cup 3
Apple with skin Medium 3
Banana Medium 3
Orange Medium 3
Strawberries 1 cup 3
Whole-wheat spaghetti, cooked ½ cup 3
Barley, cooked ½ cup 3
Carrots, cooked ½ cup 2
Blueberries ½ cup 2
Brown rice, cooked ½ cup 2
Oatmeal, cooked ½ cup
Whole-wheat bread 1 slice 2
Spinach, raw 1 cup 1
Apricots dried 4 slices 1
Enriched pasta ½ cup 1
Corn flakes 1 cup 1
White rice ½ cup 0
White bread 1 slice 0
Grits, cooked ½ cup 0
Rice cereal 1 cup 0

Source: USDA Nutrient Database; www.nal.usda.gov/fnic/foodcomp/search

References:

[1] Park Y, Hunter DJ, Spiegelman D, et al. Dietary fiber intake and risk of colorectal cancer: A pooled analysis of prospective cohort studies. Journal of the American Medical Association . 2005;294(22):2849-57.

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