Unstirred water layers in rabbit intestine: effects of guar gum.

Guar gum has been shown to affect the absorption of several different nutrients in clinical studies; however, the mechanisms for decreased absorption have not been defined. A possibility not studied with regard to guar gum, but previously demonstrated to be important in absorption, is the effect of change in the unstirred water layer. As the unstirred water layer increases in thickness, the rate of absorption decreases for certain nutrients. The effect of guar gum on the unstirred water layer in the lumen of rabbit jejunum was examined by previously described techniques. It was observed that: increases in guar gum concentration resulted in an increased thickness of the unstirred water layer; for any stir rate, the addition of guar gum increased the thickness of the unstirred water layer; and stir rate is inversely related to the thickness of the unstirred water layer. It was concluded from these results that guar gum increases the thickness of the unstirred water layer in rabbit jejunum. This mechanism may explain, in part, the reduction of the rate of absorption of certain nutrients seen following guar gum ingestion.