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Special Edition: Fiber

Prebiotics boost gut health while adding functionality

By Hank Schultz , 11-Dec-2012

Prebiotics are the thin end of the wedge in the new era of beneficial functional fibers.  Gone are the days where mere ‘regularity’ was the goal;  now fiber is understood to provide biochemical benefits in addition to just plain bulk, and prebiotic fibers are the most biochemically beneficial of the bunch.

Prebiotics fall into several groups;  most often called upon by formulators is the polysaccharide known as inulin and its related fructans derived from chicory root or other sources. There are fructooligosaccharides (FOS) and galactooligosacharrides (GOS)  which can be derived from other polysaccharides or can be built up from smaller sugars like glucose enzymatically.  And, recently, spirulina, a whole algae product, has been marketed for prebiotic benefits.

What unites them all is their ability to survive being torn apart in the stomach to arrive intact in the lower GI tract, where beneficial bacteria ferment these robust molecules and churn out the short chain fatty acids so favored by epithelial cells as a metabolic substrate. 

Functional, not finicky

And prebiotics can do this without some of the drawbacks of probiotics.  Because they are essentially carbohydrate food sources for bacteria, rather than the bacteria themselves, they don’t require the careful handling to keep them alive, and the fussing about with dosages to make sure the bottle claim of the number of colony forming units are still viable when the consumer downs the pill, according to Bob Hutkins, PhD, a professor in the Food Science and Technology Department of the University of Nebraska at Lincoln.

“A lot of people are interested in prebiotics for the way in which they to enhance health and improve the composition of the gastrointestinal tract in contrast to probiotics because these things don’t require all the biological care you need with a probiotic like keeping it alive and using big doses,” Hutkins told NutraIngredients-USA.

“Causing changes in the gut composition via a probiotic is real challenge.  You have to take big doses and you have to take them regularly.  The (baseline) gut community is really well established; for a newcomer to be successful is a big challenge,” he said.

“That’s assuming that under the best of circumstances they all were able to survive the trip. If they get there can contribute to health but their life expectancy down there is not good.

“But with a prebiotic you are relying on the bacteria that are already residing in that habitat and the data is really strong, convincing in my opinion, that you can cause these shifts (in species distribution) in a positive way with prebiotics,” Hutkins said.

Shotgun vs. sniper rifle

From the standpoint of hitting a target distribution of gut bacteria, though, probiotics are far more precise.  You’ll have a few billion new workers punching in in your internal chemical factory a few hours after ingestion, and you’ll know who they are.  Using a probiotic is a little like hunting moose with a shotgun.  You can spray the willows with pellets, and be reasonably sure of covering your general target area.  But there can be dozens of different species and strains of lactobacilli or bifidobacteria resident in any given gut (the genuses mostly likely to benefit from prebiotics), so there is know way of knowing which species and strains will predominate after a prebiotic feast.

“Which isn’t necessarily a bad thing, because we know so little about what specific strains can do anyway,” Hutkins said. “The benefit of a probiotic is specific to that strain, but there are not too many strains for which there are real good claims.

“If a prebiotic will boost your bifidobacteria or your lactobacilli by an order of magnitude or two, it could have some pretty dramatic effects on your gut well being,” he said.

Functionality beyond fiber

Another benefit from the formulator’s point of view is the functionality of these carbohydrates.  FOS and GOS can have benefits such as modulating the creaminess of certain formulations, and some of these molecules have a slight sweetness, which can serve to slightly reduce the amount of other sweeteners needed.

Ingredion manufactures a probiotic ingredient called NutraFlora which is a short-chain fructooligosacharride made from cane sugar via fermentation.  In addition to its prebiotic benefits, the ingredient is faintly sweet and can help balance sweetness profiles when used in conjunction with high intensity sweeteners, said Cristina Munteanu, senior food technologist with Ingedion.  The FOS molecules found in NutraFlora are the shortest available on the market, which is important for their prebiotic functionality, Munteneau said.

“That’s important because some of research we’ve done with NutraFlora we’ve found that some of the essential bacteria in our digestive system are very specific to the chain links that they can utilize. 

“Lactobacilli are beneficial bacteria in our gut and they have a preference for three or four chain links. If it is too big a molecule, they can’t use it,” she said.

Newer prebiotic sources  include teh aforementioned spirulina, marketed by Valensa and UAS Labs in a combined pre- and probiotic product called Probiogreen, and a hemicellulose extract from spruce trees that has shown prebiotic properties in recent tests in Finland.

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