Biliary lipid composition and gallstone formation in rabbits fed on soy protein, cholesterol, casein and modified casein.

In four experimental groups, rabbits were fed on diets containing soy beans, soy beans plus cholesterol (1%, w/w), casein and modified casein for 8 weeks. Biliary lipid levels, lithogenic-index values and the rate of gallstone formation were determined. The highest mean relative concentrations (mol%) of cholesterol and phospholipid were found in the soy bean + cholesterol group, and the highest mean relative bile acid concentration was in the soy bean group. The lowest mean relative cholesterol and phospholipid values were found in the soy bean and modified casein groups respectively. The lowest mean relative bile acid level was in the soy bean + cholesterol group. The highest lithogenic index and rate of gallstone formation were in the soy bean + cholesterol group, and the lowest values were in the soy bean group. The modification of casein used was effective in decreasing the lithogenic effect of casein on gallstone formation.