CHAMPAIGN, Ill. -- What if a person could get the benefits of dietary fiber without eating bowlsful of bran? What if avoiding inflammatory bowel disease and ulcerative colitis was as easy as eating small amounts of the right foods?
In a turnaround from previous beliefs, researchers are finding a growing list of benefits to human and animal digestive systems from certain forms of indigestible oligosaccharides -- naturally occurring groups of carbohydrates containing simple sugar molecules -- found in many fruits and vegetables.
For years, oligosaccharides were thought to give people flatulence or diarrhea. A 1968 study of men who ate beans and other legumes found that the bad side effects were caused by stachyose and raffinose, which now are known to be undesirable oligosaccharrides. They're also found in soybeans. But other oligosaccharides actually may possess health-promoting properties.
Instead of 15 grams of fiber a day, a person need only eat about 3 grams of oligosaccharides, said George C. Fahey Jr., a professor of animal sciences and of nutrition at the University of Illinois.
"Oligosaccharides may prove to be a replacement for part of the dietary fiber that we know is useful, because they do the same things," he said. "Actually, they do better things, because they select for -- they become food for -- the same bifidobacteria and lactobacilli, which are good bacteria in the bowel. You get the same preventable substrate to the large bowel. The foods with oligosaccharides also are more pleasing, and you don't have to eat as much to get the same desired effect."
In two comprehensive studies published in the January issue of the Journal of Nutrition, U. of I. researchers documented how fructooligosaccharides and xylooligosaccharides enhance digestion.
Fahey found that in rats the pool of desirable short-chain fatty acids increased significantly in the large bowel and in the cecum, a cul-de-sac at the beginning of the large intestine. Organs where fermentation -- the enzymatic breakdown of foodstuffs by microbes -- occurs actually grew thicker and bigger. Levels of both bifidobacteria and acidity increased.
Researchers tested liquid dietary formulas on pigs and got the same results as with the rats. By adding fish oil that contains anti-inflammatory fatty acids, protective action was increased even more. Fahey suggests that people hospitalized with bowel disease might benefit from their results.
In a third study, yet to be published, Fahey's lab will report that artichoke, chicory, onion, garlic, leek, shallot, chives and asparagus contain high levels of desirable oligosaccharides. Also offering high levels are fruits such as peaches and bananas.
Working with Fahey on the rat study were graduate student Joy M. Campbell and Bryan W. Wolf, a clinical research monitor with Ross Products Division of Abbot Laboratories; Fahey was joined on the pig study by Campbell, veterinary pathobiologist Carol A. Lichtensteiger and Stephen J. Demichele of Ross Products, which funded both projects.