December 2013 Issue
Functional Fibers — Research Shows They Provide Health Benefits Similar to Intact Fibers in Whole Foods
By Constance Brown-Riggs, MSEd, RD, CDE, CDN
Vol. 15 No. 12 P. 32
High-fiber foods have been shown time and again to increase satiety, reduce heart disease and type 2 diabetes risk, and enhance digestive health. But despite these benefits, most people fall short of the recommended daily requirements, averaging only 15 g per day—far below the suggested daily fiber intake of 25 to 38 g for adolescents and adults.1
Because most Americans aren’t getting enough fiber, manufacturers are adding different types of fibers, known as isolated fibers or functional fibers, to foods and even beverages to help boost consumer intake. They’re adding soluble corn fiber, polydextrose, and soluble fiber dextrin to foods such as cereals, soups, baked goods, and meal replacements.
Read on to learn about the characteristics and health benefits these added fibers provide, as demonstrated in the current literature, and ways RDs can encourage clients and patients to increase their fiber consumption.
Sources and Physiological Effects
The Institute of Medicine (IOM) categorizes fiber as either dietary fiber or functional fiber. Dietary fibers are nondigestible carbohydrates and lignin that are intrinsic and intact in plants.2 These fibers pass through the small intestine into the large intestine, where they may be partially or completely fermented by gut bacteria. Functional fiber consists of isolated or purified carbohydrates that are nondigestible, absorbed in the small intestine, and have beneficial physiological effects in humans.2
The IOM recommends that the health care community stop using the terms “soluble fiber” and “insoluble fiber” because recent studies have suggested that other properties of fiber, such as physical and chemical structure, fermentation capacity, and viscosity, determine the effect on health outcomes and biomarkers.
For example, dietary and certain functional fibers, particularly those that are poorly fermented, improve fecal bulk and laxation and also remedy constipation. Viscous fibers may delay gastric emptying, resulting in a feeling of fullness, which may contribute to weight control. Delayed gastric emptying also may lower postprandial blood glucose excursions and have a beneficial effect on insulin sensitivity. Moreover, viscous fibers can interfere with the absorption of dietary fat and cholesterol, which may result in lower blood cholesterol levels.2
Fiber Innovations for Nutrition and Health
Emerging fiber innovations are making it easier for manufacturers to create products that can help Americans boost their fiber intake and meet daily requirements without sacrificing taste, texture, or enjoyment.
“This is a growing industry with a variety of functional fiber products coming out on the market,” says Kristi L. King, MPH, RDN, CNSC, LD, a spokesperson for the Academy of Nutrition and Dietetics (the Academy). While this trend may be growing, many nutrition professionals remain cautious about recommending products that contain isolated fibers, particularly in individuals with a history of gastrointestinal (GI) problems. For these individuals, all types of fiber can cause GI distress. “I caution anyone with delayed gastric emptying or gastroparesis,” King says. “Fiber can delay stomach emptying even further and cause discomfort.”
Patsy Catsos, MS, RDN, LD, author of IBS-Free at Last! who has a digestive health practice in Portland, Maine, worries about her patients with irritable bowel syndrome (IBS). “IBS patients often experience excess gas, bloating, and abdominal pain when they consume fiber-fortified foods,” she says.
Sonya Angelone, MS, RDN, CLT, a spokesperson for the Academy, recommends that her clients eat whole, fresh, and minimally processed foods whenever possible to obtain naturally occurring fiber. “Isolated fibers lack the natural components that may contribute synergistically to the benefit of the fiber itself,” she says.
However, research suggests that when added fibers, such as soluble corn fiber, polydextrose, and soluble fiber dextrin, are added to foods, they can help consumers increase their fiber intake without concerns about GI distress and, at the same time, confer health benefits associated with naturally occurring intact fiber sources.
Soluble Corn Fiber
Soluble corn fiber is produced through the enzymatic hydrolysis of cornstarch. It’s poorly digested in the small intestine but partially fermented by gut bacteria in the large intestine and exhibits the same physiological benefits of dietary fiber. It has a low viscosity, is water soluble, and is stable under heat, pH, and processing stresses.3
Evidence suggests that soluble corn fiber is well tolerated and has many of the same health benefits associated with intact dietary fiber found in grains, vegetables, legumes, and fruit. While high-fiber diets often are associated with GI discomfort, such as excessive gas production, studies have demonstrated that soluble corn fiber is well tolerated even at a high intake level of 65 g/day when given in multiple doses and is better tolerated than inulin, a naturally occurring fiber extracted from chicory root.3,4 Moreover, soluble corn fiber improves intestinal regularity4 and has prebiotic properties.3 When used in place of available carbohydrates, soluble corn fiber supports healthy blood glucose control by eliciting a lower glycemic response.5 It also may support bone health by increasing calcium absorption.3
Soluble corn fiber can be used in a wide variety of prepared foods, beverages, and condiments, including cereal, baked goods, candy, dairy products, frozen foods, soups, salad dressings, fruit drinks, carbonated beverages, meal replacement drinks, and flavored water. It can appear in product ingredient lists as soluble corn fiber, corn syrup, or corn syrup solids.3
Polydextrose is a polysaccharide that’s synthesized from glucose and sorbitol, a sugar alcohol made from corn syrup but also found in apples, pears, peaches, and prunes. It’s used as a bulking agent, and sometimes as a sugar substitute, in foods, and it resists digestion and absorption.
Studies show that polydextrose demonstrates positive physiological effects associated with dietary fiber.6 It’s well tolerated when given as a single 50-g dose or up to 90 g/day,7 supports blood glucose control by eliciting a lower blood glucose response accompanied by a reduced postprandial insulin response,5 and may assist in bowel regularity and support the growth of beneficial gut bacteria.7 In addition, polydextrose may assist with weight control by providing only 1 kcal/g,7 and emerging data suggest a satiety benefit.5,7
Moreover, polydextrose can be added to various foods, such as reduced-sugar, no-added-sugar, and sugar-free cereals, sauces, baked goods, beverages, and dairy products.7 It appears in product ingredient lists as polydextrose.
Soluble Fiber Dextrin
Soluble fiber dextrin, also known as resistant dextrin, is a soluble fiber that’s isolated from wheat, corn, or tapioca and is nondigestible. It has a low viscosity and dissolves in water, making it easy for manufacturers to add it to beverages and foods such as breading, sauces, soups, cereals, and yogurt. It appears in product ingredient lists as dextrin.2 One study showed that soluble fiber dextrin can promote satiety when added to beverages.8
An emerging body of research is validating the effectiveness and physiological health benefits of soluble corn fiber, polydextrose, and soluble fiber dextrin. Three new studies supported by Tate & Lyle, a global provider of specialty ingredients and the first to introduce soluble corn fiber to the food ingredients industry, add to the growing evidence in support of the health benefits of added, isolated fibers in the diet.
For example, STA-LITE Polydextrose and PROMITOR Soluble Corn Fiber are proprietary ingredients that Tate & Lyle have formulated. Evidence from their studies suggests that these specialty fibers have high tolerability and health advantages associated with intact fiber found in whole foods.
Researchers from the University of Minnesota reported that 36 healthy adults who consumed 20 g of added fiber, either STA-LITE or PROMITOR per day, in addition to their usual lower-fiber diet, which included approximately 13 to 14 g of fiber per day, experienced improved laxation with minimal GI tolerance issues.9 These results, published in the April 2013 issue of the Journal of Nutrition, indicate that both types of fiber tested in the study were well tolerated and could be successfully added to the diet to help meet dietary fiber recommendations.
“Yes, STA-LITE and PROMITOR may help someone experience improved laxation, but a diet low in fiber is probably also low in complex carbs, whole grains, nuts and legumes, and fruits and vegetables,” Angelone says. “People need to be eating a more healthful diet, which would help with laxation and also provide many other nutrients so important for overall good health and disease prevention.”
Consuming enough fiber continues to be a challenge for individuals and food and nutrition professionals. In fact, according to the International Food Information Council 2013 functional foods consumer survey, 67% of respondents thought they were meeting their fiber requirements; in reality, only 5% of consumers were getting sufficient amounts of dietary fiber. The difficulty in meeting the dietary recommendations for intact fibers from whole grains, vegetables, and fruits alone has caused many in the health care community to believe functional fibers can help consumers meet their fiber goals.
In another study using a double blind, randomized crossover design, researchers from Iowa State University found that soluble fiber dextrin can help promote satiety from 3 to 8.5 hours after consumption. Researchers provided 41 healthy adults with lunch that included a test beverage containing 10 or 20 g of fiber from soluble fiber dextrin or a control beverage containing maltodextrin, followed by a snack 21/2 hours later. The study participants who received the beverage containing 20 g of fiber reported feeling fuller and having a decreased desire to eat from 3 to 8.5 hours after consumption compared with those who drank the control beverage. The soluble fiber dextrin didn’t impact appetite or overall food intake during the first 2.5 hours postconsumption. These results indicate that soluble fiber dextrin may be slowly digested, leading to delayed effects on appetite.10
A third study examined the effect of PROMITOR on fecal microbiota in relation to calcium absorption in 24 racially diverse male and female adolescents. Researchers from Purdue University found that when the adolescents consumed 12 g of fiber per day from soluble corn fiber, they experienced a 12% increase in calcium absorption. This increase in calcium absorption was correlated with significant increases in specific strains of beneficial bacteria, including Bacteroides, Butyricicoccus, Oscillibacter, and Dialister, in the gut, suggesting that soluble corn fiber may increase calcium absorption through changes in gut microbiota.11
“A greater absorption percentage may be slightly beneficial, but a 12% increase in a diet low in calcium is still a diet low in calcium. This is still a problem,” Angelone says. “It doesn’t contribute to the dietary intake of calcium, which is significantly lacking in the diet of most people.”
But while a 12% increase in calcium absorption due to the consumption of soluble corn fiber may seem insignificant at first glance, Priscilla Samuel, PhD, director of global nutrition for Tate & Lyle, says, “The 12% increase in calcium absorption with soluble corn fiber compared to a control translates to about a 2% increase in bone calcium over one year, which would be impactful over the course of a lifetime. It’s like killing two birds with one shot. You get added fiber and increased calcium absorption.”
Helping Patients Meet Fiber Goals
According to Angela Lemond, RDN, CSP, LD, owner of Lemond Nutrition in Plano, Texas, fiber-fortified foods can help fill the gap as patients work toward increasing their fiber intake with whole foods. “For some [people] who are just starting to add more plant foods to their diet, foods that are fortified with fiber may help bridge the gap while they make efforts to increase intake of beans, fruits, and vegetables.”
King agrees: “In clinical practice, we realize that with the busy lifestyle many people lead, it can be difficult to consume the recommended 25 to 38 g of fiber per day. Some patients may tolerate one type of functional fiber better than others. So it may take some trial and error to find the one that works best for them.”
Increasing fiber in individuals with IBS also can be challenging. “Brown rice, rice bran, oatmeal, oat bran, quinoa, chia seeds, and canned, drained chickpeas and lentils are well tolerated fiber sources for IBS patients,” Catsos says.
Closing the Gap
Ideally, individuals should increase their fiber intake from whole-food sources such as whole grains, fruits, beans, and peas and other vegetables, but incorporating added fibers into foods as part of a well-balanced diet can help close the fiber gap between recommended and actual intakes. Nutrition professionals will want to stay abreast of the emerging research on the many health benefits of these functional fibers and which products contain them.
— Constance Brown-Riggs, MSEd, RD, CDE, CDN, is the national spokesperson for the Academy of Nutrition and Dietetics, specializing in African American nutrition, and author of the African American Guide to Living Well With Diabetes and Eating Soulfully and Healthfully With Diabetes.
Products Containing Functional Fibers
Soluble Corn Fiber
• Baked goods
• Dairy products
• Frozen foods
• Salad dressings
• Fruit drinks
• Carbonated beverages
• Meal replacement drinks
• Flavored waters
• Powdered drinks
• Soft drinks
• Ice cream and other frozen desserts
• Hard and soft candies as well as chocolate
• Cakes, cookies, and pies
• Cereals and snacks
• Fruit spreads
• Salad dressings
• Sauces, syrups, and toppings
• Peanut spreads
• Reduced-sugar, -fat, and -calorie foods
1. Slavin JL. American Dietetic Association. Position of the American Dietetic Association: health implications of dietary fiber. J Am Diet Assoc. 2008;108(10):1716-1731.
2. Dietary, functional, and total fiber. In: Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients). Washington, DC: National Academy Press; 2002.
3. Tate & Lyle. Soluble Corn Fibre: Health Benefits and Product Applications. http://www.foodnutritionknowledge.info/Documents/TL Soluble Corn Fibre Brochure2013.pdf. Accessed September 28, 2013.
4. Housez B, Cazaubiel M, Vergara C, et al. Evaluation of digestive tolerance of a soluble corn fibre. J Hum Nutr Diet. 2012;25(5):488-496.
5. Konings E, Schoffelen PF, Stegen J, Blaak EE. Effect of polydextrose and soluble maize fibre on energy metabolism, metabolic profile and appetite control in overweight men and women. Br J Nutr. 2013:1-11.
6. Ranawana V, Muller A, Henry CJ. Polydextrose: its impact on short-term food intake and subjective feelings of satiety in males—a randomized controlled cross-over study. Eur J Nutr. 2013;52(3):885-893.
7. Tate & Lyle. Polydextrose: Health Benefits and Product Applications. http://www.foodnutritionknowledge.info/Documents/TL PDX Brochure2013.pdf. Accessed September 28, 2013.
8. Monsivais P, Carter BE, Christiansen M, Perrigue MM, Drewnowski A. Soluble fiber dextrin enhances the satiating power of beverages. Appetite. 2011;56(1):9-14.
9. Timm DA, Thomas W, Boileau TW, Williamson-Hughes PS, Slavin JL. Polydextrose and soluble corn fiber increase five-day fecal wet weight in healthy men and women. J Nutr. 2013;143(4):473-478.
10. Hutchinson C, Hsu WH, Hollis JH. Effect of soluble fiber dextrin on postprandial appetite and subsequent food intake in healthy adults. Presented at: Experimental Biology; April 20-24, 2013; Boston, MA.
11. Whisner CM, Nakatsu CH, Martin BR, McCabe LD, McCabe GP, Weaver CM. Soluble corn fiber modulates calcium absorption by altering colonic microbiota. Poster presented at: Experimental Biology; April 20-24, 2013; Boston, MA.