Is caffeine associated with bone mineral density in young adult women?

Background. By increasing the urinary excretion of calcium, caffeine consum ption may reduce bone mineral density (BMD) and subsequently increase the r isk for osteoporotic fracture, Although negative associations between caffe ine consumption and BMD have been reported for postmenopausal women, in par ticular for those who consume low amounts of dietary calcium, the relation between caffeine and BMD in younger women is unclear. Therefore, we evaluat ed the association between caffeine consumption and BMD in a cross-sectiona l study of 177 healthy white women, age 19-26 years, who attended a Midwest ern university. Methods. Average caffeine intake (milligrams per day) was calculated from s elf-reports of the consumption of coffee, decaffeinated coffee, tea, colas, chocolate products, and select medications during the previous 12 months ( mean caffeine intake = 99.9 mg/day), BMD (grams per square centimeter) at t he femoral neck and the lumbar spine was measured by dual-energy X-ray abso rptiometry. Results, After adjusting in Linear regression models for potential confound ers, including height, body mass index, age at menarche, calcium intake, pr otein consumption, alcohol consumption, and tobacco use, caffeine consumpti on was not a significant predictor of BMD. For every 100 mg of caffeine con sumed, femoral neck BMD decreased 0.0069 g/cm(2) (95% confidence interval [ CI] = -0.0215, 0.0076) and lumbar spine BMD decreased 0.0119 g/cm(2) (95% C I = -0.0271, 0.0033), No single source of caffeine was significantly associ ated with a decrease in BMD, Furthermore, the association between caffeine consumption and BMD at either site did not differ significantly between tho se who consumed low levels of calcium (less than or equal to 836 mg/day) an d those who consumed high levels of calcium (>836 mg/day), Conclusions, Caffeine intake in the range consumed by young adult women is not an important risk factor for low BMD.