The Whole Story - Fiber, Whole Grains, & Health
Today’s Dietitian
By Victoria Shanta-Retelny, RD, LD
Vol. 7, No. 2, p. 28

Don’t let your clients be fooled by unclear labeling or caramel-colored products. Know the facts about whole grains and fiber and the role they play in disease prevention.

The nature of whole grains, with their inherent fibrous structure, has proven to have many health benefits. From lowering lipid levels to staving off diabetes and cancer to controlling blood pressure and helping with weight maintenance, whole grains can act as medicine in the body. The American Heart Association sees the power of whole grains in maintaining a healthy heart and recommends that individuals consume at least six servings per day of whole grain products such as oatmeal, cereal, bread, and brown rice.

With United States government agencies, such as Health and Human Services’ National Institutes of Health, the FDA, and the National Academies’ Institute of Medicine, aggressively promoting the necessity of whole grains and fiber in the diet, why are 100 million U.S. adults overweight or obese?1 And why has the prevalence of type 2 diabetes mellitus (T2DM) and cardiovascular disease (CVD) been escalating in countries such as China and India, which are being affected by Western affluence?2 Dietary factors are the main focus on research radar screens as numerous clinical studies have been conducted on the role of dietary fiber (or lack of) and the prevalence of morbidity rates.

Whole Grain vs. Fiber
According to Bernard Venn, PhD, of the department of human nutrition, University of Otago, New Zealand, “Defining the term whole grain has presented difficulties both in terms of analyzing and interpreting research studies and in making recommendations.” Venn explains that epidemiological studies have defined whole grain foods “as those products that comprise =25% whole grain content or bran by weight.” The FDA requires foods to contain >51% by weight of whole grain ingredients for health claims regarding whole grains and disease. “It has been suggested that analyzing the product for fiber content may provide a check of compliance with the requirement for overall whole grain content,” says Venn.

Labeling Language
The key to determining whether a product is a whole grain is the language used on the label. According to Joanne L. Slavin, PhD, RD, professor, department of food science and nutrition, University of Minnesota - Twin Cities, “Words like multigrain, 100% wheat, or bran may indicate important health benefits but [do] not necessarily mean a product is whole grain.” Her advice is to look for words such as “whole” before the first or second ingredient in the ingredient listing (ie, whole wheat or whole oats).

The Minnesota-based professor adds, “Consumers should look on packaging for either the FDA-authorized whole grain health claim or the stamp for either ‘good’ or ‘excellent’ source of whole grain.” She notes that a “good” source of whole grain contains 8 grams of whole grain per serving; an “excellent” source is 16 grams of whole grain per serving. For high-fiber items, consumers should look for 5 grams or more per serving, and a “good” source of fiber is 2.5 to 4.9 grams per serving.

More Than Fiber
Many health experts contend that the disease-preventing capabilities are found not only in the fiber but also in the “whole” grain. According to Slavin, “Fiber is the undigested part of the carbohydrate, where as the whole grain includes fiber but also the germ of the grain and the endosperm. Whole grain is a complete food, not just the isolated fiber fraction.”

Introduced as “one of the nation’s best experts on whole grains” at the American Dietetic Association’s Food and Nutrition Conference & Expo in Anaheim, Calif., last year, Slavin’s presentation, titled “The Healthy Benefits of Whole Grains,” described how the whole grain is greater than the sum of the parts. Her research has shown that the whole grain’s combined properties of resistant starch, phytonutrients, plant stanols and sterols, inulin (fiber), and antioxidants help create the total health benefits picture. Her research shows that whole grains are protective for a wide range of diseases, such as CVD, T2DM, obesity, and cancer. The whole grain expert pointed out that exactly how whole grains fend off morbidity and keep the body healthy remains somewhat of a mystery. According to Slavin, “The whole grain’s mechanisms of action are still being studied but currently include its effects in the colon, as an antioxidant, and changes in glucose metabolism.”

Weight Loss: Benefits of Whole Grains and Fiber
How does eating more whole grain, high-fiber products aid in weight loss? At any given time in the United States, approximately 44% of women and 29% of men report that they are attempting to lose weight, and 5 million of these adults have used prescription drugs for treatment of obesity.3,4 National authorities have recommended greater consumption of grain products to control weight because of the belief that diets rich in fiber are generally low in saturated fat.5 Jenkins et al found that whole grains may have beneficial effects on weight control through promoting satiety. The reason for this increased full feeling is that whole grains slow down starch absorption, which has the positive domino effect of lower insulin and glucose responses and oxidation and lipolysis of fat rather than its storage.6,7

According to an analysis of prospective data from the 1984 to 1996 Harvard Nurses’ Health Study (NHS) published in the American Journal of Clinical Nutrition (2003), diet may affect body weight through multiple pathways, including satiety and metabolic efficiency, or through modulation of insulin secretion and action.8 Since the 1960s, the increase in the intake of refined carbohydrates in the form of processed grains, soft drinks, sugars, and refined flours in the U.S. food supply has been reported to parallel the increased prevalence of obesity and diabetes.9 The data from the NHS revealed that weight gain was inversely associated with increases in the intake of whole grains but positively associated with increases in the intake of refined grains.8 According to Slavin’s interpretation of the Harvard study, “Women who consumed more whole grains consistently weighed less than women who consumed fewer whole grains.” In other words, proper weight control involves increasing dietary fiber and distinguishing whole grain from refined grain products for consumers.

Whole Grains and Diabetes
“The structure of the grain is important to the glycemic response to food,” says Venn. For example, the milling of wheat efficiently separates the bran, germ, and endosperm to produce finely ground flour. Once those separate parts are reconstituted, whole meal flour is produced. “Bread made from finely ground whole meal flour has a glycemic index [GI] of 71 +/- 2, no different than that of white bread,” emphasizes Venn. (GI of 100 is equivalent to raw sugar.) In contrast, bread made from whole or cracked wheat has a GI 20% to 30% lower than white bread, thus indicating that grain structure affects the metabolism of the carbohydrate content possibly by influencing the slowing rate of digestion and absorption.10

The earliest suggestion that refining whole foods may be implicated in the etiology of T2DM stems from observations that the frequency of diabetes increased in populations as unprocessed or lightly processed food were replaced by refined products.11 Historically, it has been observed in Britain between 1940 and the mid-1950s that incidence of death from diabetes dropped with the introduction of “national flour,” less-processed flour, which replaced refined grains. Not surprisingly, the diabetes rates rose again after the use of national flour ceased.12

The postprandial glycemic response to grains with an intact structure (eg, whole oats, whole wheat, cracked wheat) would appear to be lower than when the grain structure has been disrupted, such as in whole meal wheat bread, barley flour bread, and rolled oat porridge.10 Thus, the benefits of eating whole grain, high-fiber foods rather than their refined counterparts are essential for good glycemic control. However, research reveals that most grain products in the United States are highly refined.8,9 Refined grain products have been stripped of their outer layers, and as a result have a higher starch and greater energy density but lower fiber content than whole grains. The important components of whole grain products—vitamins, minerals, essential fatty acids, and phytochemicals needed for carbohydrate metabolism—are lower in refined grains.10

Dietary fiber, such as soluble fiber, has been highly studied for its effects on diabetes. Some studies in people with or without diabetes have shown that soluble fiber added to test drinks or meals induces a lower glycemic response.10 Interestingly, there is a phenomenon called the second meal effect. Venn describes this phenomenon as “the glycemic and/or other physiological responses to a standard meal fed several hours after the feeding of a previous meal.”

It has been shown that the consumption of a breakfast having a low GI lowers the glycemic response to a standard lunch taken four hours later compared with the same lunchtime meal following a higher GI breakfast.13 One theory for this is that rapidly digested carbohydrate can result in large rises in insulin followed by rapid falls in blood glucose. This may cause serum fatty acid release, which can result in impaired carbohydrate tolerance.13 The second meal effect is still being studied as a possible link to fiber and glycemic response. “Several studies have indicated that meals having low glycemic indices beneficially affect the glycemic response to the following meal,” says Venn.

The conclusion to many studies related to whole grain’s effect on diabetes is that whole grains protect against the development of this chronic disease. Whole grains are now recognized as a major preventive measure for the onset of type 2 diabetes. Consumption of whole grains is associated with improved insulin sensitivity and improved metabolic outcomes.2 “Recommendations for whole grains are now included in the 2002 American Diabetes Association evidence-based recommendations for diabetes prevention,” says Slavin.

DASH Diet Link
Fiber has been identified as one of the key dietary components of the Dietary Approaches to Stop Hypertension (DASH) diet. In a recent research brief in the Journal of the American Dietetic Association, Marlene M. Most, PhD, RD, FADA, associate professor, research, at Pennington Biomedical Research Center, Baton Rouge, La., looks at the effects of the fiber in combination with the phytonutrients in the DASH diet as contributory factors to lowering blood pressures. The DASH diet, which is rich in fruits, vegetables, and whole grains, provides an abundance of plant-based nutrients.

Plant-based diets are associated with a reduced incidence of chronic diseases.14 Consumption of whole grain foods with the protective effects of dietary fiber, vitamins, minerals, antioxidants, phytosterols, and other phytochemicals lowers CVD risk.15 One proposed theory for risk reduction is that the complex mixture of phytochemicals in a diet containing fruits, vegetables, and whole grains has important complementary, additive, synergistic, or inhibitory actions.9 It is important to note that although certain nutrient targets were achieved with the design of the DASH diet, its focus on high fiber with fruits, vegetables, and whole grains surrendipitously contribute a multitude of other beneficial compounds to the diet.14

Nutrient Density
As nutrition educators, the challenge is getting people to believe that more is less. Eating more nutrient-dense food with less calories will aid in weight loss and stave off chronic diseases. According to Maye Musk, MS (Dietetics), MS (Nutritional Sciences), RD, CDN, a nutritionist in private practice in New York City, part of a healthy lifestyle is eating more nutrient-dense, high-fiber foods, such as fruits, vegetables, and whole grains. Musk’s “Density Diet” espouses the virtues of nutrient-dense foods, which increase satiety with fewer calories. “When you eat nutrient-dense foods, the quantity is large, but the calories are not,” explains Musk. The diet’s recommendations hone in on plenty of fiber with 4 cups of vegetables, 3 fruits, 3 servings of whole grains, 1/2 cup legumes, and 2 tablespoons nuts or seeds (including flaxseeds) per day.

“The most immediate effect of a high-fiber diet is on bowel health and regularity of bowel movement,” says Venn. He explains that these are important considerations when educating consumers. “A consumer-friendly message is that food fiber has been found to encourage growth of good bacteria in the gut and discourage growth of harmful bacteria.”

With 71% of consumers claiming that they make some effort to consume whole grains, according to USDA surveys, nine out of 10 people are not getting enough fiber in the way of whole grains. “Consumers’ definitions are rooted in misconceptions,” according to Susan J. Crockett, PhD, RD, FADA, director, Bell Institute of Health and Nutrition. Her marketing research found that consumers think whole grain is brown, only wheat, the same as multigrain, and bad-tasting (sweetness denotes not whole grain). The best way to educate consumers is to motivate them to read labels for fiber content and whole grain statements.

By piquing consumer interest and providing compelling messages about the health benefits and clearing up myths about fiber and grain products, more people are apt to use less-refined, healthier products. As a result, we may see a decline in the incidence of chronic diseases in the United States and other countries influenced by Western culture.

— Victoria Shanta-Retelny, RD, LD, is a practicing dietitian at Northwestern Memorial Wellness Institute in Chicago, a freelance food and nutrition writer, and a culinary spokesperson.

References
1. Kuczmarski RJ, Carroll MD, Flegal KM, Troiano RP. Varying body mass index cutoff points to describe overweight prevalence among U.S. adults: NHANES III (1988 to 1994). Obes Res. 1997;5:542-548.

2. Venn BJ, Mann JI. Cereal grain, legumes and diabetes. Eur J Clin Nutr. 2004;58(11):1443-1461.

3. Serdula MK, Mokdad AH, Williamson DF, et al. Prevalence of attempting weight loss and strategies for controlling weight. JAMA. 1999;282(14):1353-1358.

4. Khan LK, Serdula MK, Bowman BA, Williamson DF. Use of prescription weight loss pills among U.S. adults in 1996-1998. Ann Intern Med. 2001;134(4):282-286.

5. U.S. Department of Agriculture and U.S. Department of Health and Human Services. Nutrition and your health: Dietary guidelines for Americans. Washington, D.C.: Government Printing Office; 1995.

6. Jenkin DJ, Jenkins AL, Wolever TM, et al. Starchy foods and fiber: Reduced rate of digestion and improved carbohydrate metabolism. Scand J Gastroenterol. 1987;129(suppl):132-141.

7. Jenkins DJ, Wesson V, Wolever TM, et al. Wholemeal versus wholegrain breads: Proportion of whole or cracked grain and the glycemic response. BMJ. 1988;297(6654):958-960.

8. Lui S, Willett WC, Manson JE, et al. Relation between changes in intakes of dietary fiber and grain products in weight and development of obesity among middle-aged women. Am J Clin Nutr. 2003;78(5):920-927.

9. Ludwig D, Peterson K, Gortmaker S. Relation between consumption and insulin resistance: Lessons for humans and animals. Proc Nutr Soc Austr. 1998;22:158-167.

10. Foster-Powell K, Holt SH, Brand-Miller JC. International table of glycemic index and glycemic load values. Am J Clin Nutr. 2002;76(1):5-56.

11. Trowell H. Diabetes mellitus and dietary fiber of starchy foods. Am J Clin Nutr. 31 (10 suppl):S53-S57.

12. Trowell H. Diabetes mellitus death-rates in England and Wales, 1920-70, and food supplies. Lancet. 1974;2:998-1002.

13. Jenkins DJ, Wolever TM, Taylor RH, et al. Slow release dietary carbohydrate improves second meal tolerance. Am J Clin Nutr. 1982;35:1339-1346.

14. Most M. Estimated phytochemical content of the dietary approaches to stop hypertension (DASH) diet is higher than in the Control Study Diet. J Am Diet Assoc. 2004;104(11):1725-1727.

15. Anderson JW. Whole grains protect against atherosclerotic cardiovascular disease. Proc Nutr Soc. 2003;62(1):135-142.

Research Reveals Powerful, Previously Unknown Cancer-Fighting Activity in Whole Grains
Using a new method, researchers have discovered that whole grains such as corn, whole wheat, oats, and brown rice exhibit a level of anticancer activity that is equal to and sometimes greater than the level known to occur in vegetables and fruits.

In findings reported at the American Institute for Cancer Research (AICR) International Conference on Food, Nutrition and Cancer, researcher Rui Hai Liu, MD, PhD, and his colleagues at Cornell University found that whole grains contain many potent antioxidants that have gone undocumented for years because researchers have not known how to look for them.

The finding may begin to clear up one of the most controversial and confusing questions in contemporary diet-cancer science: the role of high-fiber diets in lowering colon cancer risk. For years, scientists have wondered why populations that consume diets high in fiber-rich whole grains consistently have lower risk for colon cancer, yet short-term clinical trials involving small groups of subjects yield inconsistent results.

The answer may lie in the fact that clinical trials have tended to overlook a possible role for whole grains in favor of focusing on the role of fiber alone in lowering colon cancer risk, often to the point of giving subjects isolated fiber supplements. Liu’s revelation about whole grains’ protective activity suggests that future clinical studies would benefit from a broader perspective—one that accounts for the collective, interactive effects of whole grains themselves, the fiber they contain, and the various protective substances Liu’s work has revealed.

“This research also serves to underscore the need for Americans to opt for whole grain choices whenever they can,” says Melanie Polk, RD, AICR director of nutrition education. “Whether it’s boiling up some whole wheat pasta, asking for brown rice at an Asian restaurant, trying unusual grains like millet and kasha, or simply making sure that your bread is 100% whole wheat, we have more reasons than ever to make room for whole grains.”

Fiber Tips for Consumers
1. Scan food labels for bread and cereal products listing whole grain or whole wheat as the first ingredient.
2. Look for cooked and ready-to-eat cereals with at least 3 grams of fiber per serving.
3. Eat raw fruits and vegetables; they have more fiber than cooked or canned foods or juices. Dried fruits (especially dried figs) are also good sources of fiber.
4. Increase fiber in meat dishes by adding pinto beans, kidney beans, black-eyed peas, bran, or oatmeal.
5. Try adding 2 to 3 teaspoons of unprocessed wheat bran to foods such as meatloaf, casseroles, homemade breads, muffins, and other baked goods.
6. Dairy foods provide little fiber. Increase fiber by adding fresh fruit, whole grain or bran cereals, nuts, or seeds to yogurt or cottage cheese.
7. Chopping, peeling, cooking, pureeing, and processing may reduce fiber content.
8. Substitute oat bran for one-third of all-purpose flour in baked goods recipes.
9. It is best to eat a variety of foods and not to rely on a fiber supplement.
10. Do it gradually—rapid fiber increase may result in gas, cramping, bloating, or diarrhea.
11. Drink plenty of fluids—at least 8 cups every day.

Subscribe to Today's Dietitian Magazine!