The Secret Garden
“In the antiseptic American culture, talking about healthy bacteria is an oxymoron,” says Wendy Reinhardt Kapsak, MS, RD, director of health and nutrition at the International Food Information Council (IFIC, Washington). “Unaided, consumers do not mention prebiotics as a healthful ingredient; however, they do mention whole grain and other fibers as components beneficial to digestive health, likely because those foods are grounded in long-held associations,” she says. She was summarizing findings from IFIC's May 2005 survey, “Consumer Attitudes toward Foods for Health.”
A prebiotic is a non-digestible food ingredient that benefits the host by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon and, thus, improves host health (Gibson, G.R. and Roberfroid, M.B. 1995. Journal of Nutrition). Some of the more common commercially available prebiotics are resistant maltodextrin, polydextrose and inulin. Prebiotics are fermented by bacteria into short-chain fatty acids (SCFA), the proliferation of which decreases pH.
“Prebiotics benefit both the bacteria in the product and in the colon,” explains Hilary Hursh, a food and nutrition scientist at an inulin supply house. A study conducted by her company measured the viability and vitality of bacteria in symbiotic products (products containing both prebiotics and probiotics) using simulated digestion. In such products, more bacteria survived through the product's shelflife and simulated digestion, she summarizes.
Prebiotics have been shown to boost immunity, produce natural antibiotics and help decrease toxic substances in the body. Certain studies suggest inulin prevents the formation of colon cancer. In addition, prebiotics aid in overall digestive health by preventing the growth of pathogens and decreasing recovery time after diarrheal diseases.
Prebiotics help increase the concentration of SCFAs (by-products of fermentation), which, in turn, lowers the colonic pH. The lower pH is theorized to help increase the amount of soluble calcium that can be absorbed by the body. Also, inulin has reportedly stimulated beneficial bacteria that help mediate carbohydrate and lipid metabolism, reducing levels of LDL (“bad”) cholesterol.
“Just talking about prebiotics does not help [promote] digestive health, because pre- and probiotics go hand in hand,” says Reinhardt Kapsak. The popularity of probiotic products like Lifeway Foods' (Morton Grove, Ill.) kefir has helped gain awareness of digestive health. In fact, more probiotic products are now incorporating prebiotics. Although there is no official definition of probiotics for regulatory purposes, the Food and Agriculture Organization of the United Nations (FAO) defines probiotics as “live micro-organisms which, when administered in adequate amounts, confer a health benefit on the host.”
Five years ago, Julie Smolyansky, president of Lifeway Foods, became aware of prebiotics and, in early 2005, decided to add inulin to Lifeway's low-fat and organic lines. “I expect that it is going to be a positive addition to Lifeway because it is a value-added nutrient that doesn't affect the taste or formulation of my products,” considers Smolyansky.
Microflora MealsMost prebiotics can be added to bread, ice cream, yogurt or meat. They generally are very soluble in water and can be added to water without producing any taste or appearance. They are very versatile and can be incorporated into any food product. “Consumers are looking to baked goods, but we have worked on confections, hard candy and chocolate as a novel way to supply people with prebiotic benefits,” offers Hursh.
Polydextrose has been on the market for 25 years and has a proven history of use in a variety of food applications. Without having any sweetness, it can be used in combination with a high-intensity sweetener if sweetness is desired, and it is easy to incorporate at higher levels due to its neutral taste.
Compared to some other prebiotics, polydextrose is beneficial, as it is fermented throughout the entire length of the colon. Fermentation in the distal (or latter) part of the colon has been pinpointed as more beneficial to health, says Donna Brooks, product manager at a prebiotic sweetener company.
Since polydextrose is well-tolerated (at a mean laxative dose of 90g/day), it can be used in various applications such as ice cream, nutrition bars, confections, baked goods and beverages.
Lactitol is a polyol or sugar alcohol with many of the same physiological properties as sucrose, but is only 30%-40% as sweet as sugar. It can be added to replace the bulk of sugar, or it can be used to reduce the amount of sugar if less sweetness is desired, while still maintaining bulk for functionality. Lactitol is typically used in ice cream, chocolate, confections, cakes and cookies.
Inulin, a chicory root extract, is a broad term covering all of the degrees of polymerization (DP) of fructose polymers. Fructo-oligosaccharide (FOS) is a short-chain inulin that extends from 2-10 fructose units. Inulin stimulates the growth of the bifido species bacteria. There is a benefit from inulin at a usage level of as little as 1.25g-2g/serving. However, health benefits are dependent on the DP and the amount of the prebiotic in the product. Combinations of inulin and FOS, as with polydextrose, also can be digested along the entire length of the colon.
Inulin and FOS are soluble fibers and are easy to work with to replace starch or sugar portions. In comparison to other types of fiber, inulin does not disturb the gluten structure in baked goods. It also is hygroscopic, shown to be beneficial in nutrition bars because it keeps the bar soft over a longer shelflife.
With a sweetness range from 0%-30% of the sweetness of sugar, inulin also provides flavor masking in high-protein formulas and helps to mask the flavor of high-intensity sweeteners. Inulin contributes to browning because it has reducing sugars. “That can be a positive or negative, depending upon the product,” says Hursh. “In addition, because inulin has a positive heat of solution, it helps to mask the cooling sensation from polyols, which have a negative heat of solution.”
Fraternal or Identical PhysiologyBesides those mentioned earlier, a number of other compounds have potential as prebiotics, such as soybean oligosaccharides (raffinose, stachyose), lactulose, isomalto-oligosaccharides, lactosucrose, gluco-oligosaccharides, palatinose and resistant starches.
There are several doctrines about what criteria define a prebiotic. “Almost all prebiotics are fiber, and almost all dietary fibers are prebiotics; but some fibers are better sources of prebiotics,” opines Dennis Gordon, a consultant and the emeritus professor and chairman of the Department of Cereal Science at North Dakota State University (Fargo, N.D.). Both prebiotics and fiber are resistant to digestion. According to Gordon, fiber has two main purposes: laxation (because fiber cannot be digested in the small intestine), and being a source of energy for colonic microflora. “Almost all fibers (with few exceptions) are a source of energy and, thus, a prebiotic,” he says. Compared to all forms of dietary fiber, prebiotics are simply a more efficient source of energy. Microcrystalline cellulose (MCC) is one rare exception because it is so inert to the body that it is not fermented and passes through the body, notes Gordon. To be defined as a source of dietary fiber, a non-digestible carbohydrate must have a DP of three or greater.
Even some hydrocolloids are prebiotic. Guar gum, for example, is a very viscous polymer, but is fermented when it gets to the colon. However, depending on the formulation, it is not a good prebiotic because a very small amount makes a thick solution and it is not cost effective when compared to other prebiotics, says Gordon.
Generally, the smaller its molecular weight and the greater its surface area, the more easily a fiber can be fermented and, thus, be a potential prebiotic, Gordon offers. For example, wheat bran is a good source of fiber and a gold standard for laxation, but inulin is better as a prebiotic because inulin can be completely fermented. Depending on how finely ground the wheat bran is, the body would pass greater than 50% of what is ingested. “What is not adding stool volume and passed with feces is fermented and used by the bacteria,” explains Gordon. Increased fermentation confers increased bacterial activity, favoring the growth of acid-producing bacteria that also enjoy an acidic environment--one wherein pathogenic bacteria do not survive.
Not everyone agrees that all fibers are prebiotics. “Just because it is fermented in the colon doesn't mean that it stimulates the beneficial bacteria,” says Hursh. Fiber is related to physiological benefits that are not available in every prebiotic, such as increased transit time, stool softening, and blood glucose or cholesterol attenuation, says Brooks, who suggests that lactitol is a prebiotic but not a fiber.
Nevertheless, Gordon and others agree that prebiotics cannot replace whole grains. However, when consumed as a part of a varied diet, they complement the entire dietary fiber picture. “A diet [based] solely on prebiotics is not a healthy diet,” says Gordon.
Prebiotic Word PlaySteve Riccardelli, vice president of North America-marketing at Sunsweet Growers Inc. (Yuba City, Calif.), says that in marketing PlumSmart juice, with chicory root, the company's goal was to appeal to mainstream consumers by positioning the juice as an aid for digestive health. “For this reason, we don't use the term prebiotic because some consumers believe that we might be adding something artificial,” he explains. “It's possible to get too deep and give them more information than they want.”
“What we hear from manufacturing customers is that consumers are not ready [to digest this information] yet,” says Brooks, echoing Riccardelli's comment. “We're still educating the food industry. Consumers are one step away.” For consumers, the top two sources of information for health and wellness are media and health professionals, says Reinhardt Kapsak. Sponsoring educational sessions for these two segments, and providing them with highly credible, easily digestible information they can pass on to consumers is one way manufacturers can increase awareness.
Nevertheless, manufacturers should be careful to use the right words when communicating about prebiotics and digestive health. “It's important that [manufacturers and health professionals] meet consumers where they are at, versus where they want them to be,” says Reinhardt Kapsak. For example, she suggests that consumers are more receptive to terms like “digestive health” and not “intestinal” or “gut health.”
Consumer awareness about the relationship between prebiotics and digestive health will continue to increase over time as they come into contact with more information--especially if they are hearing the same messages from multiple sources, says Reinhardt Kapsak. “It takes a long time to establish awareness and, ultimately, understanding of the relationship. Consumers may already be consuming a prebiotic but, currently, they are not connecting it to probiotic benefits.”
The current FDA recommendations surrounding fiber give manufacturers an opportunity to discuss the added benefits related to symbiotics. “Fiber is a point of entry to talk about prebiotics,” says Reinhardt Kapsak. “We can use what they know about fiber to build their awareness of prebiotics.”
Going Global“Consumers in the U.S. are a little squeamish when talking about digestive health, but it is more widely accepted in other countries,” says Reinhardt Kapsak. Many of the prebiotic and probiotic products that are gaining attention in the U.S. are derived from culinary staples in other parts of the world. Kefir, for example, traces its history back 2,000 years to the Caucasus mountains of Russia where people supposedly not only live well past their 100th birthday, but also have fewer instances of cancer, diabetes, obesity and many other illnesses. Inulin is found naturally in fruits, vegetables and whole-grain foods that many indigenous cultures consume regularly.
Previously, Westerners suspected that the decreased mortality in these communities was because they kept their microbiota “well fed.” Today, science has demonstrated strong correlations between overall health and digestive health. A search on Mintel International's (Chicago) Global New Products Database (GNPD) shows, from 1999 to July 2005, that of 205 products containing the word “prebiotic,” only 7 products appeared in the U.S. This implies that Asian and European countries have “stomached” the idea but U.S. consumers continue to balk at intestinal health, says Gordon.
Stomach Improvement Council, a dairy-based and yogurt-flavored prebiotic drink produced by DyDo Drinco (Osaka, Japan) uses fermented milk, 180mg of oligosaccharide, isomalto-oligosaccharide, soy polysaccharide and gluconic acid for functional positioning. A prebiotic Mexican-style bread spread, Mexico Prebiotischer Vital-Aufstrich Spread, by Fredy's (Traiskirchen, Austria) is vegetarian, cholesterol-free and rich in fiber. Fructo-oligosaccharide (FOS) is an influential ingredient in Mango Twist Buah + Susu Drink, which Heinz ABC (Jakarta, Indonesia) debuted in May 2005. It is promoted as having 6% calcium and enriched with prebiotics and vitamins. Prebiotic ingredients in infant foods are popular in many countries around the world. Kalbe Pharma Health Foods (Sanghiang, Perkasa) launched Milna brand Green Bean Rusks in March 2005. Advertising green bean-flavored rusks with DHA and 380mg FOS for prebiotic action, the product is said to be suitable for babies from four months of age as a porridge and from six months of age as a biscuit.