The Functionality of Probiotics and Prebiotics

Probiotic means for life, as derived from the Greek, and a probiotic is a living microorganism considered beneficial to the human body. These beneficial bacteria are found naturally in various fermented foods, including yogurt, tofu, sauerkraut and miso. In fact, history has long hinted at the longevity of those consuming fermented foods rife with probiotics. In one Old Testament version, a passage states Abraham owed his longevity to his regimen of sour milk. Centuries later, Roman historian Plinius recommended fermented milk products for treatment of gastroenteritis. And the health benefits of probiotics were scientifically elucidated by early microbiologists, including Louis Pasteur, who discovered the importance of microorganisms for life, and Elie Metchnikoff, who won a Nobel Prize in 1908 for his efforts.

Metchnikoff postulated intake of Lactobacilli from yogurt could reduce toxin-producing bacteria in the gut, increasing the host persons longevity.

The human gut is inherently abundant in bacteria, both beneficial and harmful. There are some 100 trillion bacteriabetween three and four poundsin the gastrointestinal (GI) tract; these microorganisms affect digestive health, immune health and nutrient absorption. There are also some amounts of bacteria in the mouth and skin. However, it is the gut that plays the biggest role in overall health and longevity. The balance of microflora in the gut is crucial to GI integrity and, subsequently, the absorption of vitamins, minerals and other micronutrients the body needs to operate and fend off pathogens. In fact, gut microflora are responsible for breaking down certain vitamins and fermenting fibers and other carbohydrates not digested in the upper GI tract. Fatty acids produced by certain gut bacteria help maintain a healthy gut barrier. Lactobacilli can convert sugars into lactic acid, inhibiting the proliferation of certain harmful bacteria, while also lowering the pH of the gut. Bifidobacteria convert dietary fiber to lactic acid. The increase in lactic acid is thought to possibly help those with lactose intolerance.

These probiotics also help preserve gut health by competing with harmful bacteria for receptor sites along the intestinal wall.

However, not every strain of these bacteria confers health benefits. There are about 400 strains of probiotics, most of which are of the lactobacilli or bifidobacteria genus. There are a lot of strains out there that are the same genus and species as a more researched strain, but they are really just a substrain, explained Michael Shahani, director of operations for Nebraska Cultures, which offers the DDS-1 strain of L. acidophilus. One kind of L. acidophilus may not do exactly the same thing as another strain of acidophilus. He said while the substrain may have some similar effects, it is far more advantageous to find and use a strain that is well researched for certain benefits.

Tim Gamble, vice president of sales and marketing with Nutraceutix, explained since the healthy gut contains dozens of strains with potential health benefits, it is up to the formulator to decide on developing and marketing a product, based on research, to address specific conditions with specific strains. As long as the probiotic product contains non-genetically modified, naturallyoccurring organisms found in the human gut, and are manufactured and delivered professionally, effectively and in accordance with GMP [good manufacturing practice] standards, then the product will have merit, he contended.

Probiotics are popular for lowering the risk of or limiting the progression of various digestive ailments, including constipation, irritable bowel syndrome (IBS), general intestinal viruses and diarrheaboth travelers and antibiotic-induced. According to the National Digestive Diseases Information Clearinghouse (NDDIC), as many as 70 million Americans are affected by digestive diseases and conditions, from diarrhea to cancer, costing upwards of $86 million in direct medical expenses alone. Beyond digestion, certain probiotic strains have been shown to affect absorption and metabolism of certain minerals, such as calcium and iron. Other researched effects include inhibiting colon cancer development, lowering cholesterol and blood pressure, reducing inflammation and inhibiting Helicobacter pylori (H. pylori), which causes stomach ulcers. This broad range of healthy activity has sparked interest in functional uses of probiotic ingredients, as Americans increasingly prefer to supplement via palatable foods and beverages than a pill or capsule.

However, putting probiotics in foods and beverages is not so simple.

To get maximum or sufficient benefit from probiotic ingredients, there are a few key goals to keep in mind. While some probiotics work in the mouth and stomach and other areas of the upper GI tract, the majority do their grandest work in the lower intestines, where they attach to the intestinal wall. Thus, it is crucial to get as many intact bacteria down to the intestines. Challenging this victory is the stomach, whose harsh acid and bile spell danger for bacteria.

Unfortunately, as many studies have demonstrated, this means unprotected probiotics (powders, plain capsules, etc.) deliver very few, if any, viable organisms past stomach acids to optimal sites in the intestines, Gamble warned. Delivery technologies designed to protect probiotics from stomach acids and then release them in the intestines are a necessity for highly viable and effective probiotic supplements.

From the supply side, probiotics face numerous opportunities to die off before even reaching the manufacturer, let alone the store shelf or a consumers intestines. The first step is maintaining a quality growing process. Bacteria have to be stabilized to the point where they will actually grow and stay alive, Shahani said. Once they are in that environment, they grow on moisture, food source and warmth. He noted probiotics are mostly anaerobic, so they can grow in a place where there is not much oxygen.

There are only a handful of probiotic growers who really possess the experience, expertise and commitment necessary to do this consistently over time from batch to batcha key for any brands probiotic product to reach and maintain long-term success, Gamble said.

There is also the issue of identification. A concern more commonly associated with herbal ingredients, ensuring the strain delivered from the supplier is the strain promised can be tricky. However, newer DNA testing has made it easier for manufacturers to identify various strains, although the testing is not foolproof. Once identified properly, the challenges only get more abundant.

By nature, some bacteria will always die off in any circumstance. However, in trying to deliver as many viable probiotics as possible to the consumers lower GI tract, it is important to minimize die-off during the manufacturing and packaging processes. A huge factor in manufacturing certain functional foods is heat, which can kill substantial amounts of probiotic cells. Probiotics are also especially sensitive to moisture. Exposure to these factors during manufacturing, packaging or storage will significantly reduce the products shelf life, in addition to reducing the consumers benefits. Due to these sensitivities, some functional products just will not work for probiotics. For instance, a functional beverage would not be ideal for including probiotics, because the bacteria would be immersed in liquid while sitting on a shelfmoisture causes bacteria to grow and die offand beverages are typically stored at room temperature for longer periods of time. A better beverage solution might be a dry drink mix packaged to resist heat and other exposures. To boost the chances an ideal number of probiotics survive to ingestion, drink mix packets and any other product containing probiotics should be refrigeratedduring both shipping and shelf storage. On the other hand, it might not be as vital to refrigerate a nutritional bar, as most bars are quite dry, limiting exposure of the probiotics to moisture. But, overall, refrigeration can help any probiotic product. Many a probiotic supplement has failed to meet label claim, possibly due to die-off related to various exposures during growing, manufacturing, packaging and storage.

Even when the probiotic food or beverage reaches the consumers mouth, the journey is not over. Not only must the probiotics survive the harsh upper GI tract, but they must reach the lower intestines in sufficient numbers. Some products claim millions of organisms, but you really need billions of organisms per gram, Shahani said. Thus, many manufacturers over-formulate to account for die-off throughout the entire process.

How to get these billions of probiotics past the stomach is one of the most daunting tasks facing formulators. Despite certain marketing claims to the contrary, no particular probiotic strains are significantly more capable than others (in an unprotected form) to survive exposure to stomach acids, Gamble noted. This has been supported by research using standard USP methodology for simulation of the human stomach. He suggested using appropriate delivery technologies, such as Nutraceutixs BIO-tract® delivery system, which forms a protective layer around the probiotics and controls their release in the intestines. This technology also utilizes LiveBac® processing to extend shelf life.

While enteric coating is a viable solution for tablets and capsules, it is not so useful for functional foods. Microencapsulation is an option for foods. Institut Rosell offers Probiocap, a microencapsulation of freeze-dried probiotics designed for use in certain food products. According to the company, the technology enhances probiotics viability in new applications such as powders, cream-type formulas (e.g., chocolate bars) and processed foods. Inproprietary studies, microencapsulated L. acidophilus Rosell- 52 incorporated into chocolate had a survival rate of 91 percent; 60 percent of microencapsulated probiotics in white chocolate were still viable after 25 days of storage at 45°C, and nearly 100 percent of the probiotics in white chocolate pralines survived after six months of storage at room temperature.

However, Shahani repor ted Nebraska Cultures is not convinced microencapsulation is useful, saying you can lose a lot of bacteria in the process: It can come down to the question of whether you want to lose the bacteria on the front end or back end?

Despite the numerous challenges in using probiotics in functional foods, the demand for new probiotic innovations has not waned. Suppliers are getting requests for all kinds of functional products, including cereals, food bars and various beverages. This interest is good exposure for the probiotic industry and the awareness of probiotics health benefits. However, with the challenges to effective probiotic delivery described above, it becomes obvious that delivering viable organisms to the consumers intestinal tract in functional foods and/or beverages presents some difficult challenges, Gamble reported. Still, successful manufacturers and formulators are open to figuring out what they need to do to make a particular functional product work, no matter how impossible the request. If manufacturers are willing to learn and make the necessary adjustments to the process, we are confident the functional food industry can use more probiotics, Shahani said.

Food for Life

Prebiotics

are indigestible dietary fibers that provide a food source for bacteria. Oligosaccharides dominate this category, including fructooligosaccharides (FOS), inulin, arabinogalactans and lactulose. These fibers are found naturally in plants, namely chicory, and can be, in some cases, produced enzymatically from sugar. Passing unscathed through the stomach, prebiotics are fermented by gut microflora and selectively stimulate the growth and activities of bacteria.

In addition to enhancing the benefits of probiotics, prebiotics can also improve absorption of minerals, including calcium and magnesium, as well as inhibit development of cancer and various digestive ailments. FOS and inulin are particularly favored by lactobacilli and bifidobacteria. Thus, prebiotics have become as much a target for use in functional foods as have probiotics.

The multifunctional actions of prebiotic fibers and the various application possibilities that are available allow food producers to bring extra value and health benefits to the consumer, said Coni Francis, Ph.D., R.D., scientific affairs manager for GTC Nutrition.

But not all prebiotics have the same effect. When comparing prebiotics, the glucose terminals and short-chain length are extremely important to the fermentation profile and ingredient functionality, Francis noted. The chemical structure and relative chain length of a prebiotic will determine how easily it can be used by probiotic bacteria. GTC supplies NutraFlora scFOS, a specific, defined mixture of glucose-terminated fructose chains with a maximum chain length of five units and 95-percent pure active prebiotic. It is fermented from sugar cane.

In addition to offering the traditional benefits of dietary fiber, some prebiotics can also act as additional sweeteners, enhance a products flavor and are low in calories. scFOS is 30-percent as sweet as sucrose and provides only 1.5 kcal/g, Francis said. It also has the ability to enhance the flavor of foods, mask metallic notes associated with high intensity sweeteners and help minimize off flavors of soy-based products. Other functional benefits include its capability of improving moisture retention and enhancing the texture of extruded products, such as bars and snacks.

Francis reported scFOS is ideal for numerous functional applications, with recent requests including kefir, yogurt and other dairy applications, sports products, functional waters, nutrition bars, weight loss products, soymilk, green foods, probiotic supplements, mineral supplements, medical foods, pet foods and more. Because NutraFlora is 95 percent shortchain FOS, it is a perfect fit for these products, as inclusion rates are low and the health benefits many, she noted.

According to Cargill Health & Food Technologies, inulin from chicory is also ideal for certain functional foods. It is suitable for use in a diabetic diet and, as a food ingredient, does not significantly affect blood sugar levels. The company offers Oliggo-Fiber®, a family of fructo-oligosaccharide molecules with different chain lengths or degrees of polymerization (DP), based on the number of fructosyl units. Native FOS molecules extracted from chicory range in length from two to 60 DP with the average of eight to 10 chain lengths. Cargill said it can provide functional foods manufacturers custom forms of Oliggo-Fiber® products, with specific functional properties and applications based on longer (average DP = 20) or shorter chain lengths.

Another ingredient with prebiotic activities is acacia gum, an ancient Egyptian remedy from acacia tree. Colloïdes Naturels International reported its FIBBREGUM acacia ingredient survives the stomach intact to be fermented in the colon by lactic acid bacteria. Proprietary studies have shown 10 g/d of acacia gum can increase quantities of lactobacilli and bifidobacteria and reduce presence of disease-causing Colostridium sp. A few of its formulation advantages include being low caloric, low glycemic and safe for teeth. Also, the company noted, unlike low viscosity fibers such as oligosaccharides, acacia gum does not affect osmotic pressure in the gut and is, therefore, not laxative but is comfortably tolerated.

Also sourced from a tree is larch arabinogalactan, a long-chain, indigestible polysaccharide fiber from the larix species. As with other prebiotics, arabinogalactans are fermentable by gut microflora, produce beneficial fatty acids and convey numerous health benefits such as optimizing gut health, boosting immune health and lowering cholesterol. However, whereas inulin ranges in pH from 4 to 7, larch arabinogalactans are pH stable, thus they can be more easily incorporated into low pH beverages, such as fruit drinks.

Joining Forces

Considering prebiotics provide a food source for probiotics, it makes sense that many formulators seek to use combinations of these ingredients, called synbiotics, in functional products. Prebiotics and probiotics are synergistic and may be coupled together in products, Francis confirmed. However, while prebiotics fertilize bacteria, there are some limitations.

The only downside is that prebiotics are not universalthere is not one prebiotic that all bacteria are going to grow well on, Shahani advised. There could be an instance where a prebiotic will work well with one type of probiotic but not with others.

Enzymes also work well in combination with probiotics. Many enzymes work symbiotically with probiotics, which themselves can produce some digestive enzymes. Enzymes, depending on type, are active at different locations in the digestive tract, with differing impacts on digestion, Gamble said. Combinations of these separate ingredients should be well considered, and manufacturers carefully chosen, prior to bringing a combination product to market.

Combining numerous strains of probiotics is equally tricky. Some researchers and doctors, however, like single-strain products because they are closer to the medical model of single components and are easier to test than multiple strains, said Mairi Ross, senior product developer for Sedona Labs, which manufacturers probiotic finished products. She added some manufacturers prefer single strain formulas because they are less expensive to make. Shahani noted multiple strains can get expensive because each strain needs to be in sufficiently high concentration to be effective, which increases costs dramatically. He further advised a product with 10 or more strains might not deliver all the expected benefits. We are seeing many products using lots of strains, he said. The problem is they are going to compete for the same food source and space. Bacteria compete with each other, its how they are.

Overall, formulating probiotics and prebiotics into functional formulas presents numerous challenges to consider. However, as companies develop better technologies for improving shelf life and delivering these ingredients safely to the intestines, and as manufacturers and suppliers increasingly work together to solve the issues facing these ingredients in certain functional products, consumers will have more food and beverage options to go along with the traditional supplement forms.