Dietary garlic and onion reduce the incidence of atherogenic diet-induced cholesterol gallstones in experimental mice

Mice fed with diet containing 0·5% cholesterol for 10 weeks resulted in cholesterol supersaturation in gallbladder bile which promoted the formation
of cholesterol gallstones (CGS). In this study, dietary hypocholesterolaemic spices, garlic and onion (both raw or heat-processed) were
examined for their antilithogenic potential by including at 0·6 and 2·0% level, respectively, along with lithogenic (LG) diet for 10 weeks. Dietary
garlic and onion reduced the CGS incidence by 15–39%, the effect being maximum in the heat-processed onion group. Dietary garlic and onion
markedly reduced biliary cholesterol. The cholesterol:phospholipid ratio which was 1·58 in the LG diet group was reduced to 0·73–0·96 in the
garlic and onion groups. The biliary cholesterol saturation index was 0·92, 1·25, 1·09 and 0·86, respectively, in the heat-processed onion, raw
garlic, heat-processed garlic and raw onion groups, while it was 1·9 in the LG group. The hydrophobicity index of bile was 20·08, 20·079,
20·032 and 20·073, respectively, in the heat-processed onion, raw garlic, heat-processed garlic and raw onion groups, while it was þ0·054
in the LG group. Hepatic hydroxymethyl glutaryl-CoA reductase activity was lowered in the LG diet-fed group, while dietary garlic or onion countered
this alteration and also increased the activities of hepatic cholesterol 7a-hydroxylase and sterol 27-hydroxylase. Serum and liver cholesterol
were decreased by feeding garlic or onion compared to the LG diet. Thus, dietary Allium spices exerted antilithogenic influence by decreasing the
cholesterol hyper-secretion into bile and increasing the bile acid output thus decreasing the formation of lithogenic bile in experimental mice