<P> Vegetable gum fiber supplements are relatively new to the market . Often sold as a powder, vegetable gum fibers dissolve easily with no aftertaste . In preliminary clinical trials, they have proven effective for the treatment of irritable bowel syndrome . Examples of vegetable gum fibers are guar gum and acacia Senegal gum . </P> <P> Many molecules that are considered to be "dietary fiber" are so because humans lack the necessary enzymes to split the glycosidic bond and they reach the large intestine . Many foods contain varying types of dietary fibers, all of which contribute to health in different ways . </P> <P> Dietary fibers make three primary contributions: bulking, viscosity and fermentation . Different fibers have different effects, suggesting that a variety of dietary fibers contribute to overall health . Some fibers contribute through one primary mechanism . For instance, cellulose and wheat bran provide excellent bulking effects, but are minimally fermented . Alternatively, many dietary fibers can contribute to health through more than one of these mechanisms . For instance, psyllium provides bulking as well as viscosity . </P> <P> Bulking fibers can be soluble (i.e., psyllium) or insoluble (i.e., cellulose and hemicellulose). They absorb water and can significantly increase stool weight and regularity . Most bulking fibers are not fermented or are minimally fermented throughout the intestinal tract . </P>

Which of the following is not a rich source of soluble fibers