1. The hypothesis that soya-bean saponins, by binding bile salts in the gastrointestinal lumen, are responsible for some of the plasma-cholesterol-lowering effect of soya-bean preparations, was tested. In a double-blind crossover study 50 g soya-bean flour/d, containing either 22 or 4 g saponins/kg (adjusted by ethanol extraction) was incorporated in biscuits as a substitute for biscuits or bread into the diet of ten outpatient hypercholesterolaemic men over two consecutive 4-week study periods. The diet was monitored to ensure constancy, saponin-rich foods excluded, faeces collected for bile acid and neutral sterol analysis, and blood taken for plasma lipoprotein lipid analysis.
2. Neither diet had any effect on cholesterol in any plasma lipoprotein fraction, on fasting plasma triglyceride, or on faecal bile acids and neutral sterols.
3. These results suggested that soya-bean saponins are not responsible for the hypocholesterolaemic effect of soya-bean products.