Diet and gall stones: effects of refined and unrefined carbohydrate diets on bile cholesterol saturation and bile acid metabolism.

It has been suggested that consumption of refined carbohydrate foods (notably sugar and white flour) increases bile cholesterol saturation and hence the risk of cholesterol gall stone formation. To test this hypothesis, 13 subjects with probable cholesterol gall stones ate refined and unrefined carbohydrate diets, each for six weeks in random order. On the refined carbohydrate diet, subjects ate more refined sugar (mean = SEM: 106 +/- 7 vs 6 +/- 1 g/day, p less than 0.001), less dietary fibre (13 +/- 1 vs 27 +/- 3 g/day, p less than 0.001), and had a higher energy intake (9.17 +/- 0.66 vs 7.16 +/- 0.64 MJ/day, p less than 0.001). After each diet, the lipid composition of duodenal bile and bile acid kinetics was determined. The cholesterol saturation index of bile was higher on the refined carbohydrate diet in all but one subject, with a mean value of 1.50 +/- 0.10 compared with 1.20 +/- 0.12 on the unrefined diet (p less than 0.005). On the refined carbohydrate diet, bile contained relatively less cholic acid and slightly more deoxycholic acid. There were, however, no significant differences in total or individual bile acid pool sizes. There were also no differences in the rates of primary bile acid synthesis or fractional turnover on the two diets. Consumption of carbohydrate in refined form increases bile cholesterol saturation. The risk of gall stones might be reduced by avoidance of refined carbohydrate foods.