Inhibition of colonic water and electrolyte absorption by fatty acids in man.

In healthy volunteers, the colon was perfused with isotonic electrolyte solutions with or without 2 mM concentrations of three C18 fatty acids. These were oleic acid, its bacterial by-product 10(9)-hydroxystearic acid, and ricinoleic acid, the active principle of castor oil. Hydroxystearic and ricinoleic acids reduced electrolyte and water absorption by more than 50%; a lesser reduction, observed with oleic acid perfusion, was not statistically significant. In conjunction with other data on the effects of these fatty acids on intestinal water absorption, these results suggest that C18 fatty acids may contribute to diarrhea in states of fat malabsorption by impairing intestinal water absorption. In addition, hydration of dietary fats of hydroxy fatty acids may not be essential for this effect. During perfusion, the three fatty acids were absorbed by the human colon to the same extent.