Studies of vitamin D and calcium for fracture prevention have produced 
inconsistent results, as a result of different vitamin D status and calcium 
intake at baseline, different doses and poor to adequate compliance. This study 
tries to define the types of patients, both at risk of osteoporosis and with 
established disease, who may benefit from calcium and vitamin D supplementation. 
The importance of adequate compliance in these individuals is also discussed. 
Calcium and vitamin D therapy has been recommended for older persons, either 
frail and institutionalized or independent, with key risk factors including 
decreased bone mineral density (BMD), osteoporotic fractures, increased bone 
remodelling as a result of secondary hyperparathyroidism and increased 
propensity to falls. In addition, treatment of osteoporosis with a 
bisphosphonate was less effective in patients with vitamin D deficiency. Calcium 
and vitamin D supplementation is a key component of prevention and treatment of 
osteoporosis unless calcium intake and vitamin D status are optimal. For primary 
disease prevention, supplementation should be targeted to those with dietary 
insufficiencies. Several serum 25-hydroxyvitamin D (25(OH)D) cut-offs have been 
proposed to define vitamin D insufficiency (as opposed to adequate vitamin D 
status), ranging from 30 to 100 nmol/l. Based on the relationship between serum 
25(OH)D, BMD, bone turnover, lower extremity function and falls, we suggest that 
50 nmol/l is the appropriate serum 25(OH)D threshold to define vitamin D 
insufficiency. Supplementation should therefore generally aim to increase 
25(OH)D levels within the 50-75 nmol/l range. This level can be achieved with a 
dose of 800 IU/day vitamin D, the dose that was used in successful fracture 
prevention studies to date; a randomized clinical trial assessing whether higher 
vitamin D doses achieve a greater reduction of fracture incidence would be of 
considerable interest. As calcium balance is not only affected by vitamin D 
status but also by calcium intake, recommendations for adequate calcium intake 
should also be met. The findings of community-based clinical trials with vitamin 
D and calcium supplementation in which compliance was moderate or less have 
often been negative, whereas studies in institutionalized patients in whom 
medication administration was supervised ensuring adequate compliance 
demonstrated significant benefits.