Fiber in the Diet

Fiber is the many different parts a plant that give it structure.  Dietary fibers (cellulose, hemicellulose, pectin, lignin, etc.) are the parts of a food that pass through the body undigested by human digestive enzymes.  Often it is called roughage or bulk.  There are two types of fiber:  soluble and insoluble fiber.  Insoluble fiber is not water soluble while soluble fiber is readily soluble in water and imparts a gummy or gelatinous texture to food (like oatmeal).

What Fiber Does for You

Although fiber is not digested by human enzymes, it is very important in the diet.  Fiber benefits your health by:

• Reducing the risk of cardiovascular disease
• Reducing the risk of diabetes
• Helping control body weight
• Reducing the risk of digestive tract diseases

Reducing the risk of CVD  Soluble fiber helps lower LDL (bad) blood cholesterol by delaying its absorption in the digestive tract.  Bile attaches to fiber and the cholesterol is excreted.  As well, some soluble fibers are partially converted into substances that mimic fat.  Upon absorption, they lower LDL.  Because fiber produces satiety, which makes a person feel full, many high-fat foods are replaced.

Reducing the risk of diabetes  A high fiber diet decreases glucose and insulin responses after eating a meal.  This reduces the chance of insulin resistance (IR) that often leads to type-2 diabetes.

Helping control body weight  Fiber donates little energy to the diet, however it replaces empty-calories (high-fat and high-calorie foods with almost no positive nutritional value).  Fiber also absorbs water and swells in the digestive tract delaying hunger and producing a feeling of fullness.

Reducing the risk of digestive tract diseases  Insoluble fiber helps stimulate the muscles of the colon, thereby toning and strengthening them.  Weakened colon walls may bulge causing diverticulosis (food particles get stuck in these pockets).  Insoluble fiber also helps prevent hemorrhoids, constipation, and appendicitis, and colon cancer.

How Much Fiber Does a Person Need?

The Daily Value for a person eating 2,000 to 2,500 calories per day is 25 or 30 grams of fiber, respectively.  Whereas soluble fiber reduces the risk of CVD and diabetes, insoluble fiber helps to maintain a healthy digestive tract.  Thus, both are needed in the diet.  Soluble fibers are found in barley, fruits, dried beans and peas, oats and oat bran, rye, seeds and vegetables.  Major sources of insoluble fiber are brown rice, fruits, dried beans and peas, vegetables, wheat bran, and whole grains.

High Fiber Foods