LONG-TERM LOW ASCORBIC-ACID INTAKE REDUCES BONE MASS IN GUINEA-PIGS

The effect of long-term (1 y) low to excess ascorbic acid (AA) intake on bone mass was evaluated using guinea pigs that were 12-14 d old at the start of the experiment. Dietary AA was low (0.15 g/kg diet) (n = 7), normal (0.50 g/kg) (n = 8) or excess (10 g/kg) (n = 8). After 12 m o, total body bone mineral density (BMD, mg/cm(2)) and bone mineral co ntent (BMC, g) were determined by dual energy X-ray absorptiometry. Hi stomorphometric analysis of the cancellous bone of the proximal tibial metaphysis was completed after in vivo dual fluorochrome labeling. To tal body BMD of the low AA group was 4.9% lower (P < 0.05), and total body BMC was 12.4% lower (P < 0.05) than In the normal AA group. Total body BMD and BMC were similar in normal and excess AA groups and in t he low and excess AA groups. Histomorphometric analysis indicated sign ificantly greater (P < 0.05) double-labeled bone surface, mineralizing surface, and bone formation rate in the low AA guinea pigs compared w ith the normal AA animals. Thus, there was greater bone turnover in th e low AA group than in the normal AA guinea pigs. No differences in hi stomorphometric endpoints existed between the normal AA and excess AA groups. Long-term AA deficiency, during the period of rapid growth and slower phases of skeletal maturation, resulted in bone abnormalities In adult guinea pig skeletons. Long-term dietary AA excess caused no s uch abnormalities.