Regression of preestablished cholesterol gallstones by dietary garlic and onion in experimental mice

We have recently reported the health beneficial potential of dietary garlic and onion in reducing the incidence and severity of cholesterol gallstone (CGS) during its experimental induction in mice. In the current study, the efficacy of dietary garlic and onion in regressing preestablished CGS was investigated in experimental mice. After inducing CGS in mice with a lithogenic diet for 10 weeks, they were maintained on basal diets containing 0.6% dehydrated garlic or 2% dehydrated onion for a further 10 weeks. Dietary garlic and onion, either raw or heat processed, regressed preformed CGS in mice up to 53% to 59%, whereas the regression in the basal control diet group was only 10%. The antilithogenic potency of garlic was decreased by its heat processing, but not in the case of onion. Biliary cholesterol was significantly decreased in garlic- and onion-fed animals. Biliary cholesterol saturation index and hydrophobicity index were significantly lowered by dietary garlic and onion. Serum and liver cholesterol levels were decreased by feeding these spices during post-CGS induction period. Hepatic hydroxymethylglutaryl-coenzyme A reductase activity was increased after feeding garlic and onion, whereas activities of the cholesterol-degrading enzymes cholesterol-7α-hydroxylase and sterol-27-hydroxylase were increased in spice-fed groups. These results indicate that feeding garlic and onion effectively accelerates the regression of preformed CGS by promoting cholesterol desaturation in bile. This observation is significant in the context of evolving dietary intervention strategy to address regression of existing CGS and stopping the possible recurrence.