A large meta-analysis in The Lancet supports the use of calcium supplements for the reduction of osteoporotic fractures. The authors recommend minimum daily calcium doses of 1200 mg for best therapeutic effect.
The meta-analysis was conducted to evaluate the use of calcium and combination calcium and vitamin D for the prevention of fracture and osteoporotic bone loss. The researchers, from the Centre for Complementary Medicine Research, University of Western Sydney explain, “Calcium alone, or in combination with vitamin D, has been suggested as an inexpensive treatment to prevent osteoporotic bone loss and fractures…However, there has been substantial uncertainty about its efficacy in lowering fracture rate.” They claim that inconsistent study findings and the lack of a comprehensive review of the evidence has caused the uncertainty. After analysing 29 randomised trials comprising a total of 63,897 people (mostly women) over the age of 50 years, the authors found that calcium treatment (either alone or in combination with vitamin D) was associated with a 12% risk reduction in all types of fractures and a reduced rate of bone loss of 0.54% at the hip and 1.19% in the spine. The authors say the direction of effect for fracture reduction was consistent in all studies. Compliance was found to be particularly important in achieving the benefits of calcium treatment: trials in which the compliance rate was 80% or more had a significantly greater fracture risk reduction (24%; p<0.0001). The addition of vitamin D to calcium did not significantly change the treatment effect. In addition, a history of previous fractures did not change the treatment effect. However, the fracture risk reduction was greater in individuals who were elderly, lived in institutions, had a low bodyweight, had a low calcium intake, or were at a high baseline risk. With respect to the findings in people with low calcium intake, the authors say, "This result is important since inadequate dietary calcium is prevalent throughout the world, especially in elderly people and women." The authors estimated the number needed to treat (NNT) over 3.5 years to prevent one fracture is 63. They say this is comparable to other preventive treatments such as statins (NNT = 40) and is substantially better than aspirin treatment for the prevention of cardiovascular events (NNT = 270). (Source: Tang B, Eslick G, et al. "Use of calcium or calcium in combination with vitamin D supplementation to prevent fractures and bone loss in people aged 50 years and older: a meta-analysis." The Lancet, 2007; 370: 657-66. : sanofi-aventis : September 2007)