Past and present popular weight loss strategies tend to overemphasize single nutrients, such as fats and carbohydrates. Despite their attractiveness, these trendy “low-fat” and “low-carb” diets can be difficult to adhere to in the long term because some are quite restrictive. Furthermore, other important food components are overlooked.
One such component that merits greater attention is fiber. Because it contributes bulk to the diet, it promotes satiety and maintains it for a longer period of time than other nutrients — thereby potentially reducing the numbers of extra calories consumed. In addition, most Americans consume about 15 grams of fiber per day, which is about half the amount experts recommend. Hence, people could likely benefit from increased fiber intake. As a less-restrictive and sensible approach to weight management, diets rich in fiber may also have other health benefits, such as a reduced risk of colon cancer, diabetes, and heart disease.
Fiber and Colon Cancer
Fiber has long been thought to be protective against colon cancer because it helps “sweep” cancer-causing substances out of the intestines. Studies have demonstrated mixed results; however, data from the Nurse’s Health Study in 1999 indicated that women who consumed increased fiber daily were no less likely to get colon cancer than those who ate little fiber. Another study, the Health Professionals Follow-up Study, showed similar results. In 2003, however, two studies suggested that diets rich in fiber were indeed protective, and that people who consumed them were 25 percent less likely to develop colon cancer. Furthermore, a 10-country European study involving more than half a million people has shown a significant protective effect of fiber intake. “Most between-country studies show a protective effect in the population consuming the highest amount of fiber, yet within the United States, no benefit for fiber consumption has been shown with regard to colon cancer incidence. There is no consensus as to whether or not dietary fiber protects against colon cancer,” explains Joanne Lupton, Ph.D., Regents Professor of Nutrition at Texas A&M University. “Does this mean one should not make an effort to eat fiber? The answer to that is a decided ‘no.’ Scientific discovery is a meandering process; it will take time to find out the real story here.”
Reducing the Risk of Diabetes and Heart Disease with Fiber
Research indicates that fiber may improve blood sugar (glucose) control, which is important in diabetes management. Normally, blood sugar levels rise rapidly after eating a meal. But this process slows down when meals include fiber-rich foods such as oats, barley, fruits, and vegetables. Hence, lesser dosages of insulin or blood sugar medications—as specified by a physician—may be needed.
Diabetes, high blood cholesterol, and blood clots are three important risk factors for coronary heart disease that may be modulated by fiber-rich diets. Data from the Nurse’s Health Study showed that for every 10 grams of fiber a woman consumed daily, her risk of heart disease decreased by about 20 percent. Large-scale studies on men have shown that those who ate the most fiber-rich foods (35 grams/day) had one-third fewer heart attacks than those with the lowest fiber intake (15 grams/day). Men who ate more than 25 grams fiber/day had a 36 percent lower risk of developing heart disease than those who consumed less than 15 grams daily.
Impact of New Fiber Terms
The current protocols for labeling and defining fiber in the United States and many other countries are not yet standardized because of the emphasis on fiber as a measured food component rather than a nutrient with demonstrable health effects. However, experts are recognizing that as the science behind carbohydrates continues to evolve, new terms that define fiber, such as “nondigestible carbohydrates” (i.e., not digested or absorbed in the human small intestine) may be needed to encompass the emerging continuum of beneficial health effects and novel fiber sources. The National Academy of Sciences’ Institute of Medicine (IOM) proposed the following terminology:
Dietary fiber consists of nondigestible carbohydrates and lignin (a non-carbohydrate substance bound to fiber) that are intrinsic and intact (i.e., naturally occurring) in plants. (Examples: gums, cellulose, fiber in oats, and wheat bran.)
Added fiber consists of isolated, nondigestible carbohydrates which have beneficial physiological effects in humans. They may be extracted or modified from plants (e.g., resistant starch from green bananas and cooked, cooled potatoes) or animal sources (e.g., chitin and chitosan, found in crab and lobster shells).
Fiber benefits our immunity and overall health.
It is uncertain how these new terms will be used to help educate consumers and guide their food choices. Nevertheless, it is possible that the current system of labeling for dietary fiber—insoluble and soluble—could be replaced by two values described by the following terms: dietary fiber and added fiber. Dietary fiber would likely include plant foods in which the fiber is relatively intact and nutrients other than fiber (i.e., vitamins, minerals, and antioxidants) are present and may contribute to overall health benefits. Added fibers would delineate only those fibers that demonstrate positive health benefits. In the future, some food ingredients may be classified as “Added Fibers” on food labels, thus providing an opportunity to highlight information on anticipated health benefits.
Fiber Recommendations
The proposed new fiber terms are not expected to significantly influence recommended intake levels, although the IOM’s Food and Nutrition Board has developed adequate intakes (AI) for total fiber consumption. Men aged 14 to 50 years should get 38 grams of total fiber per day, and women aged 19 to 50 years should get 25 grams per day. Men and women over the age of 50 are advised to consume 30 and 21 grams per day, respectively. At these recommended levels, total fiber may prevent constipation, lower blood sugar and cholesterol levels, and provide a source of nutrient rich, low-calorie foods that could contribute to satiety. To illustrate how these amounts translate into food servings, see Table 1.
Some Tips for Increasing Daily Fiber Intake
Choose high-fiber (5 grams or more per serving) breakfast cereals with bran or fiber in the name. Or add a few tablespoons of unprocessed wheat bran to your favorite cereal.
Switch to whole-grain breads (which contain at least 3 grams of dietary fiber per serving). These breads list whole wheat, whole-wheat flour, or another whole grain as the first ingredient on the label.
Eat more brown rice, barley, whole-wheat pasta, and bulgur.
Eat more beans, peas, and lentils. Add kidney beans to canned soup or a green salad. Or make nachos with refried black beans, baked tortilla chips, and salsa.
Eat fruit at every meal and snack on fresh/dried fruit, raw vegetables, low-fat popcorn, or whole-grain crackers.
| Table 1. Fiber Content of Some Common Foods* |
| Food Item | Fiber Content (grams) |
| Apple, medium with skin | 3.7 |
| Broccoli, boiled, 1 cup | 4.5 |
| Brown rice, cooked, 1 cup | 3.5 |
| Carrots, raw, one medium | 2.2 |
| Kidney beans, red, boiled, 1 cup | 13.1 |
| Oat bran muffin, medium | 5.2 |
| Oatmeal, quick, regular or instant, cooked, 1 cup | 4.0 |
| Popcorn, air popped, 2 cups | 2.4 |
| Whole-wheat bread, 2 slices | 3.8 |
| *Other foods can also contribute fiber to the diet. Read food labels to find the amount of dietary fiber in each product, or search the U.S. Department of Agriculture (USDA) National Nutrient Database Web site: http://www.nal.usda.gov/fnic/foodcomp/search/ |
Prebiotics and Inulin
A prebiotic is something that feeds, or stimulates the growth of “good” bacteria in the gut and inhibits the growth of harmful bacteria. Information on prebiotics, such as inulin, may appear on food product labels in the near future. Inulin is a fiber-like compound found naturally in many foods e.g., chicory, onions, leeks, and garlic and it has received much attention lately because of its prebiotic effects. “All fiber acts as a prebiotic, in varying degrees,” explains Dennis Gordon, Ph.D., professor emeritus, North Dakota State University. “By feeding our intestinal eco-system, fiber benefits our immunity and overall health.”
Who Says it’s High Fiber?
The US Food and Drug Administration (FDA) has defined the following terms for food labeling:
High fiber = 5 grams or more of fiber per serving
Good source of fiber = 2.5 grams to 4.9 grams of fiber per serving
