Caffeine does not affect the rate of gain in spine bone in young women.

The effect of nutrition and dietary caffeine consumption and physical activity on bone gain in women during the third decade of life was determined in a longitudinal, descriptive study of 145 healthy college-aged women. Estimates of caffeine and other dietary intakes were determined by repeated 7-day diet diaries. Measurements of bone mineral in the spine and total body mineral content were determined by dual-photon absorptiometry. Measures of physical activity were ascertained by physical activity monitor. The mean estimated caffeine, calcium and protein intakes for the young women students were 103 +/- 106 mg/day (mean +/- SEM), 831 +/- 334 mg/day (mean +/- SEM) and 66 +/- 16 g/day (mean +/- SEM) respectively. The median rates of bone gain were 5.9% for spine bone mineral content, 6.8% for spine bone mineral density and 12.5% for total body bone mineral. In a multiple regression analysis the significant predictors (+ or -) of the rate of gain were age (-), activity (+), calcium intake (+) and protein intake (-). Caffeine consumption was not associated with significant reduction in rates of bone gain. While calcium and protein nutrition affect bone gain in the third decade of life in women, moderate caffeine intake (one cup of coffee per day, or 103 mg) appears to be safe with respect to bone health in this age group.