Reply
SIR—As Dr Grant states, Trivedi and colleagues showed a statistically significantly reduced incidence of fractures in their trial using cholecalciferol (D3) [1], while we in our trial used ergocalciferol (D2, the only commercially available preparation of high-dose vitamin D in Britain) and observed no reduction in fractures. However, we do not think that the different vitamin D preparation explains the difference in efficacy. The serum concentration of 25-hydroxy vitamin D was measured in subsets in both trials: in our trial, it increased by 27 nmol/l (from 47 nmol/l immediately before the first dose to 74 nmol/l after 3 months, immediately before the second dose), whereas in the trial of Trivedi and colleagues, it increased by 21 nmol/l (from 53 to 74 nmol/l). The increase in serum concentration was therefore no greater in the cholecalciferol trial despite the greater reduction in fractures. Moreover, two trials published last year (and so not included in the meta-analysis that Grant cites), recording as many as 930 new fractures between them, both used cholecalciferol (D3) in a dose equivalent to about 800 IU per day, yet like our trial they showed no decrease in the incidence of fractures in treated patients (relative risk was 1.01 in both trials) [2, 3]. As we stated in our paper, there does appear to be conflicting evidence between trials as to whether vitamin D supplementation prevents fractures, but we do not think that this has a simple explanation in terms of either dose or the vitamin D preparation used.
Wolfson Institute of Preventive Medicine, Charterhouse Square, London, EC1M 6BQ, UK Tel: (+44) 020 7882 6268; Fax: (+44) 020 7882 6270; Email: m.r.law{at}qmul.ac.uk
* To whom correspondence should be addressed
References
- Trivedi DP, Doll R, Khaw KT. Effect of four monthly oral vitamin D3 (cholecalciferol) supplementation on fractures and mortality in men and women living in the community: randomised double blind controlled trial. BMJ 2003; 326: 326–469.
[Free Full Text] - Porthouse J, Cockayne S, King C et al. Randomised controlled trial of calcium and supplementation with cholecalciferol (vitamin D3) for prevention of fractures in primary care. BMJ 2005; 330: 1003–8.
[Abstract/Free Full Text] - The RECORD Trial Group. Oral vitamin D3 and calcium for secondary prevention of low-trauma fractures in elderly people (randomised evaluation of calcium or vitamin D): a randomised placebo-controlled trial. Lancet 2005; 365: 1621–8.[CrossRef][ISI][Medline]
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