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Just Add Fiber?
Anthony, newly diagnosed with diabetes, did not know what to buy at the grocery store. “It’s all so confusing,” he said. “My dietitian told me I needed to eat more fiber, but these days, even Fruit Loops is advertising its fiber content. Does that mean it’s good for me?”
Like Anthony, anyone who has shopped at a mainstream grocery store lately has probably noticed a lot of new products touting their fiber or whole-grain content. In the bread aisle, there’s whole-grain white bread, bagels, and English muffins, as well as whole wheat bread with double the fiber. In the cereal aisle, products such as Froot Loops that used to sell themselves on the basis of taste, texture, or special added ingredients now call attention to their supposed health benefits because of added fiber. And in the dairy aisle, some formerly fiber-free products such as yogurt and cottage cheese now have 3 grams of fiber per serving.
It is no wonder that Anthony — and many others — are confused. How is it possible for white flour to be whole wheat? Does the addition of fiber make a sugary cereal a health food? And does the fiber being added to dairy products and other foods have the same benefits as the fiber found naturally in fruits, vegetables, and whole grains?
Dietary fiber is the edible part of plants that is resistant to digestion and absorption in the small intestine. Fiber is probably best known for preventing constipation, but it is also recommended for the prevention and treatment of diverticulosis (the development of small pouches in the colon that can become inflamed) and for prevention of heart disease. Fiber helps with weight control by providing a feeling of fullness in the stomach after eating.
Fiber comes in two main forms, commonly referred to as soluble and insoluble; soluble fibers dissolve in water, while insoluble fibers do not. However, some nutrition experts have started to categorize the various types of fiber by different names that better describe their effects in the body. For example, the term “viscous fiber” refers to soluble fibers that form a gummy gel during digestion. This gel slows the rate at which food leaves the stomach, helping to lower blood glucose levels after meals. Viscous fiber has also been shown to increase insulin sensitivity. And a diet high in viscous fiber can help to lower low-density lipoprotein (LDL, or “bad”) blood cholesterol levels. Good food sources of viscous fiber include oat bran, barley, nuts, seeds, beans, citrus fruits, apples, and pears.
Another term used for certain types of soluble fiber is “fermentable fiber,” because it partially or completely ferments in the large intestine. The fermented fibers are broken down into short-chain fatty acids that help to maintain the health of the colon. Food sources of fermentable fibers include oats, barley, fruits, and vegetables. (Some soluble fibers are both viscous and fermentable.)
Insoluble fiber helps to speed the passage of food through the digestive system and adds bulk to stool. Good food sources of insoluble fiber include wheat bran, legumes, vegetables, and whole grains.
Food manufacturers, who are aware of both the health benefits of fiber and the public’s reluctance to eat naturally high-fiber foods, have attempted to appeal to health-conscious consumers by adding isolated fibers (sometimes called “functional” fibers) to a variety of foods such as cereals, soy milk, dairy products, crackers, and juice. These fibers are called “isolated” because they are extracted from starchy foods or synthesized from a variety of starches and sugars. The added fibers are commonly in the form of soy, psyllium, cellulose, guar, inulin, polydextrose, oat beta-glucan, fructooligosaccharides, and digestion-resistant maltodextrin.
“Many snack bars and yogurts use inulin and oligofructose as the fiber component,” says American Dietetic Association (ADA) spokesperson and dietitian Marisa Moore. “These forms of fibers are not digested and may improve absorption of calcium and magnesium.”
But do these added fibers have the other benefits associated with naturally occurring dietary fiber?
“Most of the research has been done on intact fiber, fiber in fruits, vegetables, and whole-grain products, and not isolated fibers, which has been added to foods. Long-term studies need to be conducted on the effects of intact versus isolated fibers,” says dietitian and ADA spokesperson Toby Smithson.
Constance Brown-Riggs, also a dietitian and ADA spokesperson, adds, “Isolated fibers do not function the same as dietary fibers. While these isolated fibers are soluble, they are not viscous, they are not gummy. If these isolated fibers were gummy, then the foods they were added to would be gummy, and gummy ice cream would not sell.”
Health-care professionals do, however, agree that fiber-enhanced foods can be part of a healthy diet. “Fiber-enhanced foods can help people with diabetes control hunger, which can help with weight management and overall blood sugar control,” Moore says. These newly developed foods may help people make the transition from a lower-fiber diet to one that is higher in fiber and whole grains.
To see what effect these foods have on blood glucose, “I caution my clients to count grams of carbohydrate and monitor blood glucose before and two hours after eating to see how these foods affect their individual blood sugar,” Brown-Riggs says.
Refined whole grains
To retain the beneficial qualities of whole grains while satisfying the public taste for refined grains, ConAgra Mills has created Ultragrain, a milling process that grinds whole-grain flour so finely that it has the same particle size as traditional, refined white flour. According to ConAgra’s Web site, this milling process retains the fiber, protein, minerals, and phytonutrients, while creating a flour that has the taste, texture, and appearance of white flour. Ultragrain flour is currently used to make Wonder Whole Grain White bread and Pepperidge Farm Whole Grain Goldfish Crackers.
Agribusiness giant ADM has a product similar to Ultragrain called Kansas Diamond, a selected blend of hard white wheats that are also milled to an exceptionally fine granulation.
According to Brown-Riggs, the only difference between the new whole wheat white flours and traditional white flour is that the bran has been left in the new varieties. However, she says, “These are highly processed flours, and it is not clear if the fiber quality is maintained. Further research is needed.”
The glycemic index of breads made from these new flours is also currently not known, according to the Consumer Affairs office at ConAgra. The glycemic index (GI) is a ranking of the effect a food has on blood glucose level. Foods with a lower GI raise blood glucose less and more slowly than foods with a higher GI. Choosing lower-GI foods over higher-GI foods can therefore result in a lower blood glucose level after meals. Commercial breads made from either ordinary white flour or whole wheat flour tend to have a GI around 70, which is considered high.
Meal planning basics
To increase the fiber in their diets, Moore recommends that her clients start the day with a whole-grain cereal or toast with fresh fruit, for a total of 6–10 grams of fiber. She advises looking for cereals that have at least 5 grams of fiber per serving and bread that has 3 grams of fiber per slice. For lunch, using whole-grain bread for a sandwich, including lettuce and tomato in the sandwich, and having a side salad of mixed greens and a pear adds another 10–12 grams of fiber. For dinner, stir-frying vegetables with chicken or tofu and serving it with brown rice adds another 6–10 grams of fiber. If you eat snacks, choose fiber-containing foods such as whole-grain crackers or fruit to meet your daily fiber goals.
Moore offers some other suggestions for increasing fiber intake such as adding beans to salads, soups, and sauces (such as marinara sauce for pasta). If gas is a problem when eating beans, try using the product Beano to reduce it, or eat beans in smaller quantities at first. In place of white rice, try whole wheat couscous or a less processed grain such as barley or bulgur wheat. “Keep it simple,” Moore says, “and readily available. Try roasting a large batch of vegetables at the beginning of the week to have as a side dish for meals throughout the week.” Great roasting vegetables include asparagus, onions, carrots, peppers, and squash.
When adding more fiber to your diet, add it gradually. Adding too much fiber too quickly can cause abdominal discomfort, gas pains, and bloating. It is also important to drink more fluid — as much as eight cups a day — as you add fiber to prevent constipation.
A proven nutrient
Currently, you have to read the ingredients list on a food package to know whether the fiber listed in the Nutrition Facts panel is naturally occurring fiber or added, isolated fiber. The Institute of Medicine of the National Academy of Sciences, the organization responsible for the Recommended Dietary Allowances (RDAs), is proposing that dietary fiber and isolated fiber be listed separately on food labels. As it stands now, total fiber on food labels is the sum of dietary fiber and added fiber.
But you don’t need to wait for updated food labels to start taking advantage of the benefits of fiber. Start by consuming more naturally high-fiber foods such as whole or minimally processed grains, legumes, nuts, seeds, fruits, and vegetables. Use fiber-enhanced foods to add variety to your diet or to get in a few more grams of fiber — but not to replace the foods we know to be naturally healthy.
Statements and opinions expressed on this Web site are those of the authors and not necessarily those of the publishers or advertisers. The information provided on this Web site should not be construed as medical instruction. Consult appropriate health-care professionals before taking action based on this information.