Fiber for Health, Product Formulation (Functional Fiber)

As the functional food and beverage markets continue to grow, more formulators are looking to increase consumers’ fiber intake, owing in part to USDA’s encouraging Americans to consume at least three or more 1-oz. equivalents of whole grains per day, which can reduce the risk of several chronic diseases and may help with weight maintenance. “Given that there is a significant fiber gap among consumers of all ages, the fortification of soluble and insoluble fibers is likely to steadily increase,” said Coni Francis, Ph.D., R.D., senior manager of science, technical and marketing service, GTC Nutrition.

There are many natural sources of fiber, including fruits and vegetables, such as apples, oranges and beans; and grains, including rice and oat bran. Unfortunately, with today’s busy lifestyle and the convenience of fast food, the average person often does not meet the daily recommended intake. This is driving product developers to explore new methods to add extra fiber to processed products. “Fiber is very versatile in the benefits it can bring to the food system,” said Jim Miller, director of product management for food ingredients Americas, Tate & Lyle. “Oftentimes, people think of fiber as just adding fiber, but it also lower calories, it plays a role in satiety, it’s appropriate for low-glycemic foods and can also improve digestive health.”

Kristina Williams, vice president of marketing and sales, Natraceutical Canada Inc., echoed Miller’s statements: “Viscous soluble fiber, such as Viscofiber^®, improves glycemic response, improves cholesterol levels and increases satiety for weight loss.”

Dietary fibers are the indigestible portion of plant foods that move food through the digestive system, absorbing water and easing defecation. Dietary fiber consists of non-starch polysaccharides such as cellulose and many other plant components, including dextrins, inulin, lignin, waxes, chitins, pectins, beta-glucans and oligosaccharides. Sources of dietary fiber are usually divided according to water solubility. Both types of fiber are present in all plant foods, with varying degrees of each according to a plant’s characteristics. Insoluble fiber attracts water, which helps to increase bulk, soften stool and shorten transit time through the intestinal tract. Soluble fiber undergoes metabolic processing via fermentation, yielding end-products with significant health effects, including promoting the growth of probiotic bacteria; enhancing mineral absorption; supporting the immune system; aiding in production of short-chain fatty acids (SCFA) for gut health; normalizing glucose and blood lipid concentrations; and reducing nitrogen load on the kidneys.

Starches, which act as powerful thickeners in food products and improve food texture and structure, are also a valuable source of fiber. “Starches have been used in the food industry for more than 50 years,” said Rhonda Witwer, senior business development manager, nutrition, National Starch Food Innovations. “Resistant starch was introduced into foods as a natural fiber source in the U.S. market in 1994. Since then, when it was used as an ‘invisible fiber,’ our understanding of the health benefits of natural resistant starch has greatly expanded beyond its functionality and dietary fiber content.” Witwer added resistant starch helps control weight, regulate blood sugar, enhance energy and support the intestinal system. Benefits of Fiber

Benefits of Fiber

Obviously, fibers and starches deliver a bevy of health benefits. “Hi-maize (corn-based) resistant starch helps maintain healthy blood sugar levels in three ways,” Witwer said. “It reduces the glycemic and insulin response of foods when it replaces high-glycemic carbohydrates, such as flour; it reduces the glycemic response of the subsequent meal; and it increases insulin sensitivity in healthy people, as well as in individuals with diabetes.”

A recent study from Lund University, Sweden, affirmed Witwer’s statements, and found that including indigestible carbohydrates in the evening meal of healthy subjects improved glucose tolerance, lowered inflammatory markers and increased satiety after a subsequent standardized breakfast.¹ Scientists studied the effect of cereal-based bread evening meals (50 g available starch), varying in glycemic index (GI) and content of indigestible carbohydrates, on glucose tolerance and related variables after a subsequent standardized breakfast in 15 healthy subjects. Evening meals with barley kernel-based bread or an evening meal with white-wheat flour bread (WWB), enriched with a mixture of barley fiber and resistant starch, improved glucose tolerance at the subsequent breakfast compared with unsupplemented WWB.

In a similar study from the same group of researchers, it was discovered that glucose tolerance at subsequent meals can be notably improved during the course of a whole day or overnight by choosing specific, low-GI, whole-grain cereal products.² Twelve healthy subjects consumed test meals in a random order. In series one, the test meals were consumed at breakfast, and postprandial blood glucose incremental areas under the curve (IAUCs) were calculated after the test breakfast, standardized lunch and standardized dinner. In series two, the subjects consumed test evening meals and IAUCs were calculated after a subsequent standardized breakfast. It was concluded that a low GI may be sufficient to achieve a second-meal effect from breakfast to lunch. Researchers added that a specific indigestible carbohydrate mixture appeared to be required to show benefits on glucose tolerance in a longer time frame, most likely mediated through colonic fermentation.

Not only is fiber effective in keeping glucose levels low, it can promote satiety and weight loss as well. “Numerous studies have shown resistant starch significantly reduces body fat in animals,” Witwer added. She explained fiber helps to lower calorie density in foods when replacing flour, increases satiety in humans, switches the body to burning fat for energy instead of carbohydrates, and prevents weight re-gain “almost as much as exercise.” A 2008 study from University of Lund found subjects had higher satiety after consuming whole-kernel wheat bread.³ Equicarbohydrate amounts of the following wheat-based meals were studied: white-wheat bread, whole-kernel wheat bread or wholemeal wheat bread served with white wine vinegar. The results were compared with a reference meal consisting of white-wheat bread without vinegar. The whole-kernel wheat bread with vinegar resulted in significantly higher satiety than the wholemeal wheat bread and white-wheat bread with vinegar and the reference bread.

A study from General Mills Inc. found women consuming at least one serving of whole grain had a significantly lower mean body mass index (BMI) and waist circumference than women with no whole grain consumption.⁴

Fiber is also known to help enhance nutrient absorption. “Oliggo-Fiber™ inulin, known as the ‘invisible fiber’, may enhance dietary calcium absorption, particularly among preteens and postmenopausal women,” explained Pam Stauffer, global marketing program and communications manager, health and nutrition, Cargill. “Inulin is also recognized as a prebiotic ingredient that supports the natural, healthful bacteria in the lower gastrointestinal tract.”

Francis confirmed Stauffer’s claims, adding, “More consumers are making the connection between health and diet, and with added fiber, such as NutraFlora^® scFOS^®, many health benefits can be realized, including increased calcium absorption.” A recent French study found inulin-type fructans can modulate calcium absorption because they are resistant to hydrolysis by mammalian enzymes, and are fermented in the large intestine to produce SCFA.⁵ In turn, they reduce luminal pH and modify calcium speciation and hence solubility, or exert a direct effect on the mucosal transport pathway. The study showed an improvement of calcium absorption in adolescents or young adults by inulin-type fructans, as well as in older women.

A similar study from Baylor College of Medicine, Houston, found calcium absorption and whole-body bone mineral content were greater in young adolescents who received 8 g/d of a mixture of inulin-type fructans (ITF), compared with those who received a maltodextrin control.⁶

A healthy gut is another benefit from consuming fiber. “[GTC Nutrition’s] NutraFlora Plus Hi-maize prebiotic fiber blend, which is resistant to digestion in the upper gastrointestinal tract, is fermented by beneficial bacteria into SCFA. The production of SCFA is associated with improved digestive and immune health,” explained Francis.

A study from Harvard University, Boston, found soluble fibers are more effective than insoluble fibers in alleviating global symptoms and relieving constipation, although fiber in general has marginal benefits in treatment of overall irritable bowel syndrome.⁷ A study from Duke University, Durham, N.C., suggested daily intake of a high-fiber diet may prevent stress- and corticotropin releasing factor (CRF)-induced acceleration of colonic transit and diarrhea.⁸ Researchers studied whether dietary fiber intake affects colonic transit and motility stimulated by restraint stress and central CRF in rats. Four weeks after a corn starch, potato starch or usual diet (rat chow), colonic transit and motility stimulated by restraint stress and intracisternal (ic) injection of CRF were studied. A four-week treatment with potato starch diet significantly increased cecal concentrations of SCFAs, compared to treatment with corn starch diet. Accelerated colonic transit induced by stress and ic injection of CRF were significantly attenuated in rats receiving potato starch diet compared to rats receiving corn starch diet. The incidence of unformed stool (diarrhea) induced by stress and CRF was also reduced in rats receiving potato starch diet compared to rats receiving corn starch diet and usual diet.