Calcium supplements for the management of osteoporosis

Abstract

It seems quite impossible that a worldwide accepted ‘dogma’ like the recommendation of calcium supplementation for the prevention of osteoporotic fractures is still debated in the most important medical journals. In fact it was about 30 years ago that the first consensus statement on osteoporosis recommended a daily calcium intake of 1500 mg in postmenopausal women [1], followed about 10 years later by the recommendation of vitamin D supplementation in older adults [2], although the latter was based on extrapolation of the results obtained in very old institutionalized women to the general population [3]. The recommended intake cannot easily be achieved through diet alone, and consequently middle-aged and older women worldwide are taking calcium plus vitamin D supplements. In fact, by the early 2000s, routine supplementation to reach at least 1200 mg calcium and 800 IU vitamin D daily was a common recommendation in medical practice for the prevention of osteoporotic fractures in women aged >50, supported also by the guidelines of different influential organizations, such as the US National Osteoporosis Foundation and the Europe-based International Osteoporosis Foundation. Thus the recent publication of two systematic reviews raising serious doubts about the efficacy of calcium intake from dietary sources or calcium supplements opened a heated debate on the matter. In the first paper, Tai and colleagues [4] reported a systematic review and meta-analysis of randomized controlled trials of dietary or supplemental calcium in women and men aged over 50: 15 trials studied dietary sources of calcium (n=1533) and 51 calcium supplements (n=12,257). Increasing calcium intake from dietary sources increased total hip and total body bone mineral density (BMD) by 0.6–1.0% , with no further gains beyond the first year. This limited improvement in BMD was similar in trials of dietary sources of calcium and calcium supplements (except at the forearm), in trials of calcium monotherapy versus calcium+vitamin D, in trials with calcium doses of ≥1000 versus 500 mg/day, and in trials where the baseline dietary calcium intake was 1000 participants) randomized trials of calcium supplements, vitamin D supplements, or their combination, published to the end of 2010: • three reported a reduction in fracture risk, • nine reported no effect, and • two reported an increased fracture risk. Grey and Bolland also examined why calcium and vitamin D