BONE-MINERAL DENSITY IN A NATIVE POPULATION OF ARGENTINA WITH LOW-CALCIUM INTAKE

Objective. To determine the bone mineral density (BMD) of a group of n atives from Tafi del Valle, Argentina, to examine possible differences compared to other populations. Methods. BMD of lumbar spine and proxi mal femur was evaluated by dual x-ray absorptiometry (DEXA), in volunt eer natives of Fl Potrerillo y El Rincon (descendants of the Amaichas and Quilmes). Forty-seven women and 31 men between 20 and 80 years of age were assessed, Average daily intake of calcium, physical activity level, serum levels of 25-OH vitamin D (25-OH-D), calcium, phosphorus and alkaline phosphatase were also determined. Results. Average calciu m intake was 345 +/- 22.4 mg/day (mean +/- SD). The average sunlight e xposure was 3.8 +/- 0.44 h. Degree of physical activity was moderate/h ard (grade 4) to very hard (grade 6) in those 60 yrs of age or younger . Laboratory values were normal except for 25-OH-D levels, which were significantly greater in Tafi del Valle (26.8 ng/ml) than in Buenos Ai res (20.7 ng/ml); (p < 0.05) BMD of the proximal femur of both sexes w as significantly greater compared to the reference groups; Z score of the female population was femoral neck: +/- 0.64 (p < 0.05); Ward's tr iangle: +/- 0.64 (p < 0.001); trochanter: +/- 0.90 (p < 0.001). Among men, femoral neck: +/- 0.53 (p < 0.01); Ward's triangle: +/- 1.45 (p < 0.001); trochanter: +/- 0.95 (p < 0.001). No significant differences were observed in the lumbar spine BMD, The high physical activity requ ired by the mountainous land of Tafi del Valle may be the cause of inc reased BMD at the proximal femur among these people. High values of vi tamin D produced by increased sun exposure can lead to greater absorpt ion of calcium despite low calcium intake. Conclusion. Greater physica l activity, higher levels of vitamin D, and racial factors in the nati ve population could explain the greater BMD seen in the proximal femur despite low calcium intake.