Fiber

Dietary fiber generally refers to parts of whole grains, legumes, nuts, vegetables, and fruits that cannot be digested by humans. There are two different types of dietary fiber, insoluble and soluble. Most foods contain both types of fibers, with one type predominating over the other.

Insoluble fiber includes cellulose, hemicellulose, and lignin. Insoluble fiber does not dissolve in water. This type of fiber acts like a broom that sweeps through the colon. It aids digestion, aids elimination, promotes regularity, and contributes to bowel cleansing.

Soluble fiber, on the other hand, includes pectin, guar gum, mucilages, and algal polysaccharides. Soluble fiber has the ability to soak up water. It stimulates the peristaltic wave in the colon and binds to fats and toxins in the gastrointestinal tract and carries them out of the body. This type of fiber also increases ones feeling of fullness after a meal by expanding against the intestinal wall. Soluble fiber is helpful for lowering cholesterol, improving blood sugar balance, lowering blood pressure, and promoting the growth of friendly bacteria in the colon.

Both soluble and insoluble fibers exercise the intestinal muscles, maintaining tone and health. This promotes optimal digestive function and regular elimination.

Sources of Fiber

Richer in insoluble fiber Both soluble and insoluble Richer in soluble fiber
Wheat branWhole wheatBrown rice

Rice bran

Cauliflower

Nuts

Lentils

Green beans

Whole-grain oatsBarleySoybeans

Kidney beans

Potatoes

Broccoli

Flaxseed

ApplesOat branGuar gum

Psyllium

Pectin

Citrus fruits

 

Since fiber is found in so many foods, there are plenty of ways to add it to your diet. The daily fiber recommendation is 20 – 35 grams. The best way to increase the fiber in your diet is to add a little more each day, slowly building up to the recommended levels. (Simultaneously, you should be drinking plenty of clean water, at least ½ your body weight in ounces.) This gives your body time to adapt to the change in your diet and promotes regular digestion.

How do you know if you are getting enough fiber?  Here are some things to look for.

  • Bowel movements should be regular, daily, and effortless.
  • Stool should be almost odorless, signaling short transit time in the bowel (24 hours or somewhat less).
  • There should be little gas, if any.

 

Food Serving size Total fiber (grams) Soluble fiber (grams) Insoluble fiber (grams)
Apple, with skin 1 medium 3.0 0.5 2.5
Asparagus ¾ cup 3.10 0.81 2.29
Banana 1 medium 2.0 0.5 1.5
Black beans ½ cup 7.5 2.1 5.4
Bran flake cereal ¼ cup 5.5 0.5 5.0
Broccoli ½ cup 2.35 1.0 1.35
Cabbage ½ cup 1.75 0.8 0.95
Carrots ½ cup 1.85 .75 1.1
Cauliflower ½ cup 1.7 0.55 1.15
Collard greens ½ cup 2.65 1.2 1.45
Corn ½ cup 1.5 0 1.5
Flaxseed Meal 2 tablespoons 3.0 1.0 2.0
Green beans ½ cup 2.0 0.8 1.2
Kidney beans ½ cup 5.80 2.53 3.27
Lentils ½ cup 7.8 1.3 6.5
Oatmeal, cooked ¾ cup 3.0 1.0 2.0
Orange 1 medium 2.0 0.5 1.5
Pear, with skin 1 medium 6.0 1.0 4.0
Pinto beans ½ cup 7.35 2.8 4.55
Potato, baked with skin 1 medium 4.0 1.0 3.0
Psyllium, powder 1 rounded tsp. 4.5 3.5 1.0
Psyllium, whole husks 1 tablespoon 4.5 3.5 1.0
Raspberries ¾ cup 6.80 0.37 6.43
Spinach ½ cup 2.0 0.5 1.5
Split peas ½ cup 8.15 2.5 5.65
Brown rice, cooked ½ cup 2.4 (white = 0.5) 0.2 (white = 0) 2.20 (white = 0.5)
Winter squash ½ cup 2.85 0.3 2.55
Whole-wheat bread 1 slice 2.5 0.5 2.0

As a general rule, the foods with the highest amount of fiber from most to least (in edible form and standard serving size*) are legumes (e.g. lentils, beans–cooked) > whole grains (cooked) > fruits ≥ leafy vegetables (e.g. collards, cabbage) ≈ nuts and seeds ≈ root vegetables (e.g. carrots, beets). There is no fiber in meat, poultry, fish, eggs, or dairy products.

For a longer list giving total fiber content of foods (not divided into soluble and insoluble), go to the USDA website, http://ndb.nal.usda.gov/ndb/nutrients/ and select “Fiber, total dietary” from the First Nutrient dropdown menu.

 

Easy ways to increase your fiber intake

  • Try to consume 7 to 10 servings of whole fresh vegetables each day as well as 1 to 3 servings of fresh fruit.
  • Sprinkle nuts and seeds over dishes, such as salads, casseroles, and stir-fries.
  • Add flaxseed meal and/or chia to smoothies, muffins, breads, and casserole recipes.
  • If you choose to eat grains, choose high-fiber, whole grains instead of processed white varieties.

 

References

Kamen, Betty, PhD. New Facts About Fiber: How fiber enhances your health. Navato, CA. 1997.

Kirschman, Gayla J. and John D. Kirschmann, Nutrition Almanac, 4th Ed., Nutrition Search Inc.1996.

Nutrition Fact Sheet, Fiber Facts: Soluble Fiber & Heart Disease. National Center for Nutrition and Dietetics. 1999.

Soluble Dietary Fiber: One type of this Oldie-but-Goodie is on the Hit Parade. Healthy Buzz, May/June 1999.

* Standard serving sizes are ½ cup of cooked legumes or grains, ½ cup cooked vegetables, 1/3 cup nuts (≈ 1 ounce)