Independent and combined effects of calcium-vitamin D3 and exercise on bone structure and strength in older men: an 18-month factorial design randomized controlled trial.
CONTEXT
Exercise and calcium-vitamin D are independently recognized as important strategies to prevent osteoporosis, but their combined effects on bone strength and its determinants remain uncertain.


OBJECTIVE
To assess whether calcium-vitamin D(3) fortified milk could enhance the effects of exercise on bone strength, structure, and mineral density in middle-aged and older men.


DESIGN, SETTING, PARTICIPANTS
An 18-month factorial design randomized controlled trial in which 180 men aged 50-79 years were randomized to the following: exercise + fortified milk; exercise; fortified milk; or controls. Exercise consisted of progressive resistance training with weight-bearing impact activities performed 3 d/week. Men assigned to fortified milk consumed 400 ml/d of 1% fat milk containing 1000 mg/d calcium and 800 IU/d vitamin D(3).


MAIN OUTCOME MEASURES
Changes in bone mineral density (BMD), bone structure, and strength at the lumbar spine (LS), proximal femur, mid-femur, and mid-tibia measured by dual energy x-ray absorptiometry and/or quantitative computed tomography.


RESULTS
There were no exercise-by-fortified milk interactions at any skeletal site. Main effect analysis showed that exercise led to a 2.1% (95% confidence interval, 0.5-3.6) net gain in femoral neck section modulus, which was associated with an approximately 1.9% gain in areal BMD and cross-sectional area. Exercise also improved LS trabecular BMD [net gain 2.2% (95% confidence interval, 0.2-4.1)], but had no effect on mid-femur or mid-tibia BMD, structure, or strength. There were no main effects of the fortified milk at any skeletal site.


CONCLUSION
A community-based multi-component exercise program successfully improved LS and femoral neck BMD and strength in healthy older men, but providing additional calcium-vitamin D(3) to these replete men did not enhance the osteogenic response.