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Vitamin D and multiple health outcomes: umbrella review of systematic reviews and meta-analyses of observational studies and randomised trials

BMJ 2014; 348 doi: https://doi.org/10.1136/bmj.g2035 (Published 01 April 2014) Cite this as: BMJ 2014;348:g2035

Re: Vitamin D and multiple health outcomes: umbrella review of systematic reviews and meta-analyses of observational studies and randomised trials

The big problem with randomised trials of vitamin D supplementation is that woefully inadequate doses of vitamin D are used (e.g. 800 IU per day). Whilst the optimal blood level of (25-hydroxy) vitamin D is still a matter of debate, 100-200 nmol/L might be the ideal; the daily dose of vitamin D3 required to achieve this in adults is typically 5,000-10,000 IU per day (such doses are quite safe, as potential toxicity appears to require a sustained dose of 40,000 IU per day, and blood levels in excess of 375 nmol/L). It is thus hardly surprising when significant results are not seen – how many pharmaceutical drug trials would show a positive result if the drug being tested was given in an amount of only one-tenth of the therapeutic dose?!

Competing interests: No competing interests

04 April 2014
Peter J Lewis
Integrative physician
YourHealth
15 South Steyne, Manly, NSW 2095, Australia