Effects of dietary short-necked clam, Tapes japonica, on serum and liver cholesterol levels in mice.

Male mice were fed cholesterol-supplemented diets containing short-necked clams or defatted short-necked clams for 2 weeks under the dietary regimen of the same dietary level of protein (20%), fat (5%), and cholesterol (0.5%). Casein was used as a control protein. Similar results were obtained in two separate experiments with either boiled (Exp. 1) or steamed (Exp. 2) short-necked clams. The concentration of serum cholesterol in mice fed a clam diet was lower than in those fed control and defatted clam diets. Delipidation of clam raised the concentration of serum triglyceride. Both clams and defatted clams markedly reduced the concentration of hepatic cholesterol. Fecal excretion of neutral steroids was significantly increased by clam but not defatted clam, whereas the excretion of acidic steroids was stimulated by both specimens, in particular defatted clam. The results suggest that the hypocholesterolemic effect of short-necked clams is attributed to its lipid fraction, whereas non-lipid components contribute to the reduction of hepatic cholesterol and increased fecal excretion of bile acids.