Is caffeine associated with bone mineral density in young adult women?
BACKGROUND
By increasing the urinary excretion of calcium, caffeine consumption may reduce bone mineral density (BMD) and subsequently increase the risk for osteoporotic fracture. Although negative associations between caffeine consumption and BMD have been reported for postmenopausal women, in particular for those who consume low amounts of dietary calcium, the relation between caffeine and BMD in younger women is unclear. Therefore, we evaluated the association between caffeine consumption and BMD in a cross-sectional study of 177 healthy white women, age 19-26 years, who attended a Midwestern university.


METHODS
Average caffeine intake (milligrams per day) was calculated from self-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 the femoral neck and the lumbar spine was measured by dual-energy X-ray absorptiometry.


RESULTS
After adjusting in linear regression models for potential confounders, including height, body mass index, age at menarche, calcium intake, protein consumption, alcohol consumption, and tobacco use, caffeine consumption was not a significant predictor of BMD. For every 100 mg of caffeine consumed, femoral neck BMD decreased 0.0069 g/cm(2) (95% confidence in terval [CI] = -0.0215, 0. 0076) and lumbar spine BMD decreased 0.0119 g/cm(2) (95% CI = -0. 0271, 0.0033). No single source of caffeine was significantly associated with a decrease in BMD. Furthermore, the association between caffeine consumption and BMD at either site did not differ significantly between those who consumed low levels of calcium (< or =836 mg/day) and 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.
Conlisk
A J
AJ
Biological and Biomedical Sciences Division, Nutrition and Health Sciences Program, Emory University, Atlanta, Georgia 30322, USA. aconlis@emory.edu
Galuska
D A
DA
D015502:Absorptiometry, Photon; D000328:Adult; D015519:Bone Density / Q000187:drug effects*; D002110:Caffeine / Q000494:pharmacology*; D002136:Calcium, Dietary / Q000008:administration & dosage; D003430:Cross-Sectional Studies; D005260:Female; D005272:Femur Neck / Q000000981:diagnostic imaging; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging
D002136:Calcium, Dietary; D002110:Caffeine