The more fiber your diet contains, the fewer calories you`re likely to consume. Fiber itself yields few, if any, calories, and many fibrous foods, especially fruits and vegetables, are themselves low in calories. Also, because it absorbs water as it passes through your digestive tract, fiber is filling, and you`re more likely to feel satisfied by a high-fiber meal before you`ve overstepped your calorie quota.
That`s good news, and there`s more. But there are some precautions to observe with fiber, and we`ll get to those later.
First, besides the low calories in high-fiber foods there are other factors that undoubtedly contribute to the success of fiber in battling the bulge.
For one, it takes a long time to chew most fibrous foods. This slows down the process of eating, allowing time for the signals of satiety to reach your brain before you`ve overeaten. All that chewing also makes you feel as if you`ve eaten something substantial.
And although fiber does contribute some calories (through the fatty acids produced by gut bacteria), it may also reduce the number of calories your body absorbs from the other foods you eat. Possibly because of the decrease in gut transit time caused by fiber, small amounts of the fat and protein you eat are excreted in the feces instead of being absorbed through the small intestine. Therefore, a few of the calories you eat really ”don`t count.”
HEART DISEASE
One of the most encouraging findings about dietary fiber is the ability of some types of fiber to lower cholesterol levels in the blood. It is not known whether this will in turn reduce the risk of heart disease, but it is certainly true that in countries where the diet contains a lot of fiber (and little fat), rates of heart disease are lower than in the United States.
Here, though, is where the type of fiber consumed is especially important. Bran, which is more than 90 percent celluose, has no beneficial effect on cholesterol levels. But pectins (found in most fruits), guar gum
(found in beans) and the fiber in rolled oats and carrots can bring about a significant lowering of cholesterol.
Recent studies of oat bran have shown that daily consumption of 3 ounces
(as cereal, muffins or as a thickener in soups, sauces, purees and the like) can lower cholesterol by nearly 20 percent, which would mean a 40 percent reduction in the risk of a heart attack. Oat bran is available in many supermarkets and most health-food stores.
DIABETES
Another recently demonstrated benefit of dietary fiber is its effect on blood-sugar levels and insulin requirements. By including fiber in their diets, some diabetics under medical supervision have been able to get along without insulin or other antidiabetic medication. Here, too, pectins and guar gum are the most effective plant fibers.
An experiment at the University of Bristol in England has a telling message both for those with blood-sugar problems and those concerned about overweight and overeating. Ten healthy people were given test ”meals” of either whole apples, pureed apples (applesauce) or apple juice. Each meal contained the same amount of sugars. It took 17 minutes to eat the apples, 6 minutes to down the puree and 1 1/2 minutes to drink the juice.
It should come as no surprise to learn that the individuals reported greater satisfaction after eating the apples than after drinking the juice, with the puree producing an intermediate level of satiety. Blood sugar rose to similar levels after all three ”meals,” but the insulin level in the blood rose twice as high after the juice as after the whole apples.
One to three hours later the blood-sugar levels dropped-to normal after the apples, but to a level distinctly below normal after the juice. An intermediate but below-normal blood-sugar level occurred after the puree. These below-normal levels, called rebound hypoglycemia, are usually associated with feelings of hunger. Thus, the fiber in the whole apples reduced the demand for insulin and produced a longer-lasting feeling of satiety.
FIBER CAUSES PROBLEMS
But an increase in dietary fiber can cause problems for some people and in some cases may even interfere with good nutrition.
The most common problem, however, is not a serious one-except, perhaps, from a social point of view-and is usually only temporary. It is the tendency for dietary fiber to stimulate the formation of intestinal gas. This occurs in the large intestine, where previously undigested fiber is attacked by bacteria.
The severity of the problem is greatly reduced if you increase your fiber intake gradually (a good idea in any case, because too much fiber too soon can cause diarrhea and bloating). In most cases the problem with gas subsides in a few weeks when your gut`s bacterial population adapts to its new menu.
A more serious hazard of a high-fiber diet stems from the ability of fiber to bind other substances and carry them out of the body as waste. When these other substances are carcinogens or other noxious substances, that`s all to the good. But when they are vital nutrients, problems of dietary deficiencies can develop.
The nutrient depletions could be a problem for such people as adolescents, the elderly and the poorly nourished whose nutrient intake is borderline to begin with. Large increases in dietary fiber are inadvisable for such people.
HOW TO INCREASE FIBER INTAKE
Let`s start with the how-not-to`s. Don`t go out and buy a jar of fiber pills or tablets. Dr. Peter Van Soest, professor of animal nutrition at the New York State College of Agriculture and Life Sciences at Cornell University, points out that, ”considering the fineness and size of these pills, you`d have to eat a whole bottle of them to get any benefits.”
Don`t buy boxes of bran and pectin and use them to spruce up your otherwise unhealthy diet. Little good can be gained from adding fiber to a diet overburdened with fats and sweets. The idea is to change the kinds of food you eat, not to use fiber as a food additive. And don`t abruptly purge your diet and your household of all refined carbohydrates and replace them with natural, whole-grain kinds. A slow, gradual substitution of high-fiber for low-fiber foods will wreak the least havoc with your digestive system and be more likely to become part of your regular eating habits.
A final warning: Don`t focus on one or another type of fiber and neglect the rest. Whole grains may be the perfect cure for a sluggish gut, and any type of fiber should help you control your weight, but pectins and gums are important to how your body handles fats, cholesterol and carbohydrates.
Now for the do`s. Do make sure you consume a wide variety of fibrous foods in reasonable amounts. Be certain to drink lots of liquids when you eat fiber; otherwise fiber can be constipating instead of stimulating to your gut. In general, coarse fiber is more effective than the same fiber ground fine. Look for ”whole grain” or ”whole wheat” or ”whole oats” when shopping.
Raw fruits and vegetables have more useful fiber than those that have been peeled, cooked, pureed or otherwise processed, so include fresh fruits and raw vegetables in your daily diet. Add a ”salad a day” to the ”apple a day.”
As for how much fiber you should eat, no one can say. Certainly there are populations that consume five times as much fiber as Americans. Few Americans need or would want to eat that much fiber. But a gradual doubling of intake-say to 40 grams a day of dietary fiber (not crude fiber)-is reasonable.
Above all, remember that the watchword for fiber, as with all else in good nutrition, is moderation. If a little of something is good, that doesn`t necessarily-or even usually-mean that more is better.
