URBANA, Ill.--Guar gum, psyllium and gum xanthan had the highest viscosities of several soluble and insoluble dietary fibers in a study published in the Journal of Nutrition (136:913-19, 2006).
In the two-part study, researchers from the University of Illinois compared viscosities of corn bran, defatted rice bran, guar gum, gum xanthan, oat bran, psyllium, soy hulls, stabilized rice bran, wheat bran, wood cellulose and two methylcellulose controls (as Ticacel 42® and Ticacel 43®, from TIC Gums) after hydrating the compounds in water overnight at 0.5-, 1- 1.5-, or 2-percent concentrations. The researchers also subjected guar gum, oat bran, psyllium, rice bran, wheat bran and wood cellulose to an in vitro gastric and small intestinal digestion simulation model. Viscosity was measured every two and three hours during gastric and small intestinal simulation, respectively.
According to the results, viscosities of all fiber solutions tested were concentration- and shear rate-dependent. Rice brans, soy hulls and wood cellulose had the lowest viscosities, while guar gum, psyllium and xanthan gum had the highest viscosities, regardless of concentration. During gastric simulation, viscosity was higher at four hours than at baseline for guar gum, psyllium, rice bran and wheat bran. During small intestinal simulation, viscosities were higher between three and nine hours compared with 18 hours for guar gum, oat bran and rice bran.
The researchers concluded guar gum, psyllium and oat bran exhibited viscous characteristics throughout small intestinal simulation, indicating potential for these fibers to elicit blood glucose and lipid attenuation, whereas wheat and rice bran, and wood cellulose did not exhibit viscous characteristics during small intestinal digestion, indicating these compounds may be beneficial for laxation.