Question: I am confused about the whole issue of dietary fiber. Would you discuss this aspect of nutrition and give all of us readers some information and guidelines related to this topic?Answer: There is no question about the positive effects of dietary fiber on health. The advantages of fiber were known as far back as 430 B.C., when Hippocrates noticed that whole-meal bread improved the digestive process. But it wasn't until the early 1970s when two researchers linked dietary fiber deficiency with certain chronic diseases in Western society.
Ironically, few of our ancestors had to worry about dietary fiber because only the rich could afford refined grain products. However, as lifestyles and eating habits decreased the intake of fiber, the so-called diseases of civilization (heart disease, cancer, high blood pressure, obesity and diabetes) increased.I'll now answer some basic questions about fiber based on an article in Nestle's Worldview (Volume 3, No. 3, fall 1991):
- What is fiber? Fiber is any part of a food plant - from oranges to oats - that cannot be broken down by human digestive enzymes. There are two basic types of dietary fiber: Insoluble and soluble. Insoluble fiber is sometimes called "roughage." It remains virtually intact as it goes through the body, providing bulk that helps speed food through the system. Soluble fiber forms a gel when it comes in contact with water and increases the viscosity and stickiness of the stomach contents, slowing the passage of food from the stomach. Most plants contain some of both types of fiber.
- Where is it found? Grain products, vegetables and fruits are the principal sources of fiber in our diet. There is no fiber in meat, fish, eggs, milk and cheese.
- Why do we need fiber? Fiber promotes normal bowel function and may play a role in reducing the incidence of colon cancer. It lowers serum cholesterol levels which decreases the risk of heart disease, slows the release of sugar into the bloodstream, and makes the stomach feel full, a boon for those trying to lose weight.
- How much fiber do we need? Apparently more than we eat. The American Dietetic Association (ADA) recommends from 20 to 35 grams of fiber a day and Americans consume only 12 to 17.5 grams. Recently, a standardized method of measuring fiber has been introduced and in 1993, all FDA-approved packaged foods will list dietary fiber content on a grams per serving basis. Until then, the best way to be sure you get enough fiber is to follow the USDA's "Dietary Guidelines for Americans," which suggest the following every day:
1. Three or more servings of various vegetables (a serving is 1 cup of raw leafy greens or 1/2 cup of other kinds).
2. Two or more servings of various fruits (a serving is 1 medium apple, orange or banana; 1/2 cup of small or diced fruit; 3/4 cup juice).
3. Six or more servings of grain products such as breads, cereals, pasta and rice (a serving is 1 slice of bread; a half bun, bagel or English muffin; 1 ounce of dry ready-to-eat cereal; 1/2 cup of cooked cereal, rice or pasta).
Should you eat extra fiber with meals? Some of the benefits of fiber may be from the food that provides it, not from fiber alone. The ADA points out that too much fiber (over 50 to 60 grams a day) may actually decrease the absorption of vitamins and minerals - so get your fiber from food.