Fructo-oligosaccharides, Fructooligosaccharides (FOS)
Fructooligosaccharides (FOS) are nondigestible dietary fibers that help to keep the stomach and bowels healthy. They do this by nourishing and promoting the naturally present, "friendly" bacteria (Bifidobacteria and Lactobacilli in particular) capable of warding off infection in the digestive system. Because of these properties FOS is considered a "prebiotic." Quite popular in Japan, such prebiotics have just started to become available in the United States.
Fructo-oligosaccharides (FOS) are a group of “prebiotics,” non-digestible food ingredients that benefit the host by stimulating the growth of beneficial microflora (note: this is different than PRO-biotics, or the actual beneficial bacteria such as acidophilus and bifidum). In terms of chemistry, a fructooligosaccharide is a glucose molecule bonded to multiple fructose molecules. These bonds cannot be broken down by enzymes in the human small intestine - allowing the compound to reach the large intestine intact, where it becomes a substrate for colonic bacteria.
Short-chain FOS is metabolized in the colon (by colonic bacteria) into short-chain fatty acids. These short-chain fatty acids produce a drop in pH, which may inhibit the growth of pathogenic bacteria, facilitate intestinal calcium absorption, and act as a substrate for colonic epithelial cells. By manipulating colonic pH and microflora content, FOS may play a protective role against colon cancer. Research points to a reduction in liver fatty acid synthesis as a possible mechanism for serum lipid reduction.
Products known as "probiotics" are also gaining in popularity. These are actually live microbial foods found in various foods; the acidophilus in yogurt is a commonly recognized probiotic. Both prebiotics and probiotics can modify the composition of intestinal bacteria in beneficial ways.
FOS may benefit people who suffer from irritable bowel syndrome, a mysterious and often painful digestive disorder that can cause alternating bouts of diarrhea and constipation. The exact cause of this condition remains to be determined, but bacterial infection is one possibility. FOS's prebiotic action may help by restoring order in the bowel and controlling symptoms. In addition, preliminary research indicates that both prebiotics and probiotics may help protect the digestive tract from cancerous growths. More research is needed, however.
Natural food sources of FOS include onions, garlic, and asparagus. FOS capsules, however, provide high concentrations of a purified form of this dietary fiber.