The plasma-cholesterol-lowering effects of some dietary legumes are now well established from animal and human studies, but the mechanism is not completely understood. The present study investigated the effect of baked beans (Phaseolus vulgaris) on steroid metabolism of hypercholesterolaemic pigs. Three groups of four pigs were studied: baseline (BL), normal pigs (NP) and those previously prepared with an ileo-rectal anastomosis to nullify the function of the large intestine (IR). All three groups were given a semi-purified control diet, with about 40% energy as fat (polyunsaturated: saturated fatty acid (P:S) ratio 0.3), supplemented with 10 g cholesterol/kg, for 14 d. Then IR and NP pigs were fed for 28 d on a diet supplemented with 10 g cholesterol/kg and 300 g baked beans/kg (dry-matter basis), so that the 40% contribution to energy from fat was maintained (P:S ratio 0.3). Group BL was fed on the control diet throughout. The intact pigs (NP) fed on baked beans showed considerable differences compared with the other groups, as follows: (a) reduced plasma cholesterol (NS); (b) higher concentration of cholesterol in bile (NS); (c) higher concentration of bile acids, especially secondary bile acids, in bile (P < 0.05); (d) reduced elimination of bile acids in faeces, especially secondary bile acids (P < 0.05); (e) higher excretion of coprostanol and lower elimination of cholesterol in faeces (P < 0.05). From these findings it is proposed that a baked-bean-enriched diet potentiates bacterial fermentation and steroid degradation in the large intestine and enhances conservation of bile acids and cholesterol within the enterohepatic circulation. The high concentration of bile acids and cholesterol in bile may thus promote feedback inhibition of hepatic cholesterol synthesis, and hence, reduce plasma cholesterol.

The aim of the present study was to measure the effect of graded inclusion of baked beans (Phaseolus vulgaris) on plasma and liver lipids in hypercholesterolaemic pigs fed on a Western-type diet. Twenty- four Large White × Landrace pigs of about 30 kg body weight were made hypercholesterolaemic by feeding a semi-purified diet, high in saturated fat and supplemented with 10 g cholesterol/kg, for 14 d. After that, six pigs were randomly assigned to one of the four experimental groups. They received their respective diets, containing 0, 100, 200 or 300 g baked beans/kg, on a dry-matter basis, for a further 28 d. Fasting blood samples were taken and analysed for total plasma cholesterol, lipoproteins and triacylglycerols. After the pigs were slaughtered at the end of the study, livers were analysed for their cholesterol content. Consumption of baked beans at 100, 200 and 300 g/kg reduced plasma total cholesterol by 5·3, 20·2 and 35·6 % respectively. However, only the diet with 300 g baked beans/kg showed a significant reduction (P < 0·05) compared with the control (without baked beans)- The level of low-density-Hpoprotein-cholesterol was also significantly (P < 0·05) reduced by 48% at 300 g baked beans/kg. Plasma very-low-density-lipoprotein-cholesterol, high-density-lipoprotein-cholesterol and triacylgiycerol contents were not affected by bean consumption. The supplements of 200 and 300 g baked beans/kg promoted a significant (P < 0·05) reduction of about 50% in cholesterol deposition in the liver, compared with the control.