The relationship between serum cholesterol and fecal 7alpha-dehydroxylase activity in three ethnic groups in South Africa.

The ability of fecal bacteria to 7alpha-dehydroxylate primary bile acids was measured in vitro by incubating stool homogenates with labeled primary bile acids, and was compared to serum cholesterol levels in 4 South African groups: Rural Bantu (50 subjects), Urban White (20), Urban Bantu (17) and Urban Coloured (16). Mean serum cholesterol levels were 137 +/- 23, 213 +/- 51, 199 +/- 62 and 206 +/- 46 mg/100 ml, respectively. (Rural Bantu significantly different.) The in vitro conversion of cholic acid by stool homogenates of Rural Bantu was significantly slower than that of the Urban Whites or the Urban Bantu was significantly slower than that of the Urban Whites or the Urban Bantu in two-hour incubations. There was no difference of conversion rates in 24-hour incubations of cholic or chenodeoxycholic acids. Gas-liquid chromatographic analysis of stool homogenates showed little difference in the distribution pattern of fecal bile acids or neutral sterols. These data suggest that the activity of the intestinal bacterial flora to convert primary bile acids was significantly reduced in the Rural Bantu as compared to the other groups, corresponding with lower serum cholesterol levels. However, by the time the stools were excreted the degree of conversion was comparable in each group.