Low vs high dietary fiber and serum, biliary, and fecal lipids in middle-aged men.

Cholesterol metabolism was studied in 34 50-y-old men at home on high and low mixed-fiber diets. The high-fiber diet increased fiber intake (26.2 vs 11.6 g/d) and decreased slightly but significantly total energy, carbohydrate, and protein intakes and serum total, low-density-lipoprotein, and high-density-lipoprotein cholesterol values with no effect on dietary cholesterol and fat composition or body weight. Biliary molar lipid percentages were unaffected but deoxycholic acid was increased and chenodeoxycholic acid was decreased by the high-fiber diet. The high-fiber diet changed cholesterol absorption and fecal output of neutral and total sterols nonsignificantly but increased fecal bile acids by 13% (p less than 0.05) and reduced bacterial conversion of fecal sterols to secondary products. The decreased serum cholesterol concentration was probably caused by enhanced fecal output of cholesterol as bile acids resulting in enhanced cholesterol synthesis as indicated by an increased serum concentration of a cholesterol precursor, lathosterol.