Oxalate and its handling in a low stone risk vs a stone-prone population group

Despite hyperoxalurogenic eating habits relative to white subjects, South African blacks have urinary oxalate excretions, Tiselius risk indices (AP_CaOx) and calcium oxalate saturations, which do not differ significantly from those of their white counterparts. The present study was undertaken to establish whether the BONN-Risk-Index (BRI) might discriminate between the urines of the two population groups and whether differences might exist in their respective gastrointestinal absorption rates of oxalate. Participants (n=15 in each group) provided 24 h urines on their free diets for BRI determination. Gastrointestinal oxalate absorption was measured using the [¹³C₂]oxalate absorption test. Results showed that BRI values were significantly lower in black subjects (2.04 vs 4.90, P=0.034), but that there was no difference in the oxalate absorption between the groups (10.30 vs 9.95%, P=0.87). These results suggest that South African black subjects handle dietary oxalate more efficaciously than white subjects and that this occurs via some endogenous mechanism, which has not yet been identified or characterized.