Analysis questions calcium's benefits for fractures
supplements alone to protect against fractures in old age may be
inefficient, according to a new review by Harvard researchers.
No benefits were calculated for calcium supplements and the risk of hip fracture, according to the meta-analysis of 12 prospective cohort studies and nine clinical trials, published in this month's issue of the American Journal of Clinical Nutrition. The review draws conclusions at odds from other meta-analyses where a combination of vitamin D and calcium supplements was reported to result in significant benefits for osteoporosis, which is estimated to affect about 75m people in Europe, USA and Japan. The combination of vitamin D and calcium has long been recommended to reduce the risk of bone fracture for older people, and the use of these supplements is widely accepted by the general public. Calcium is reported to be the biggest seller in the US supplements industry. Annual sales were about $993m (€836m) in 2004, according to the Nutrition Business Journal. The authors, led by Heike Bischoff-Ferrari from Harvard School of Public Health, report no statistically significant benefit for 300 mg per day calcium intakes from seven prospective cohort studies involving 170 991 women and with 2954 documented hip fractures, and five prospective cohort studies involving 68 606 men and with 214 documented hip fractures. Moreover, clinical trials involving supplementation with 800 to 1600 mg per day of calcium did not show any benefits with respect to non-vertebral fractures and hip fracture, compared to placebo. "Pooled results from prospective cohort studies suggest that calcium intake is not significantly associated with hip fracture risk in women or men. Pooled results from randomized controlled trials show no reduction in hip fracture risk with calcium supplementation, and an increased risk is possible," wrote the authors. In an accompanying editorial, Jeri Nieves and Robert Lindsay from New York's Columbia University and the Clinical Research Center, Helen Hayes Hospital wrote: "Perhaps these data suggest that calcium supplementation, to be effective, requires the addition of vitamin D supplementation. "Calcium nutrition is intimately linked to vitamin D status, and, if 80 nanomoles per litre represents a vitamin D-replete status, then a large segment of the population-from 30 to 60 per cent, depending on the population being studied-would be vitamin D insufficient," they wrote. "Studies of calcium without regard to vitamin D status may then lead to erroneous conclusions… Those authors discussed the possibility that the efficacy of calcium intake may be enhanced by additional vitamin D but did not discuss the converse possibility - that the anti-fracture efficacy of vitamin D may be improved by calcium. "This association is of particular importance because, as Bischoff-Ferrari et al noted, recent meta-analyses have shown a decrease in hip fracture risk in persons taking both vitamin D and calcium." Nieves and Lindsay noted that compliance issues also played a part in clinical trials, and that when considering only people with good compliance, the risk of non-vertebral fractures was reduced by 17 per cent, a result similar to that reported from calcium and vitamin D trials. This however was not statistically significant. "A well-rounded diet is important, and evaluation of one element or vitamin does not give the whole story," concluded Nieves and Lindsay. "Bone is not just calcium, and calcium does not function in isolation." Source: American Journal of Clinical Nutrition December 2007, Volume 86, Number 6, Pages 1780-1790 "Calcium intake and hip fracture risk in men and women: a meta-analysis of prospective cohort studies and randomized controlled trials" Authors: H.A. Bischoff-Ferrari, B. Dawson-Hughes, J.A. Baron, P. Burckhardt, R. Li, D. Spiegelman, B. Specker, J.E. Orav, J.B. Wong, H.B. Staehelin, E. O'Reilly, D.P. Kiel and W.C. Willett Editorial: American Journal of Clinical Nutrition December 2007, Volume 86, Number 6, Pages 1579-1580 "Calcium and fracture risk" Authors: J.W. Nieves and R. Lindsay