Vitamin D

By Dr Ira Bernstein

Vitamin D has been tossed onto the hot seat this week due to a meta analysis review article. What this means is the authors have not done any original research. They have tossed together some 40 vitamin D studies over the years. The headlines in the press indicated "vitamin D supplements benefits panned in new study". Whoa.... Stop the press. Can all existing research documenting benefits ALL be wrong? The review article looked at vitamin D supplementation on skeletal, vascular or cancer outcomes. Their analyses "suggest that there is reliable existing evidence that supplementation of vitamin D with or without calcium does not reduce the incidence of myocardial infarction or ischaemic heart disease, stroke or cerebrovascular disease, cancer, total fractures or hip fractures in community-dwelling individuals by more than 15%. Vitamin D with calcium reduced hip fracture incidence in two trials of institutionalized individuals." So, let's look at this for a minute. Up to 15% reduction of anything is a benefit. Reduced hip fractures is a benefit isn't it? Are the benefits of vitamin D truly panned by this analysis?

 

I've been looking at some of the details of the article and there are issues to contend with. Firstly, much of the data is old and dates back as early as 1983. Many of the studies dosed vitamin D low (300 IU, 400 IU, 500 IU, 500 IU etc). Others dosed unconventionally (300000 IU one time dose, or 100000 IU every 4 months etc). This can muck up analyses when you have so many different variables.

Another issues that I'm having difficulty with is their cancer analysis. They include in their analysis a study from the American Journal of Clinical Nutrition, by Lappe et al 2007. Their chart display of cancer and vitamin D indicated no cancer benefit, and yet the article title is "Vitamin D and calcium supplementation reduces cancer risk: results of a randomized trial". This trial was reviewed in my nutrition course and the data clearly showed a statistically significant all-cancer risk reduction in postmenopausal women. I have no idea how the authors of the review article have erased the cancer benefits. I need a smart statistician to explain to me what they have done because I cannot figure it out.

I have posted on vitamin D before about some of the current research benefits. In my clinical practice, anyone who does not supplement with vitamin D is guaranteed to be deficient or insufficient according to current cut off levels of normal, especially in northern climates (Canada, where it seems winter is for 9 months of the year and in the summer we have floods). Vitamin D is dirt cheap (by itself) and in my lifetime, I have never seen a case of toxicity (it really does take a lot to go overboard). My suggestion is: continue to take your vitamin D. I'm not saying it is a panacea or holy grail, but in my opinion, the evidence does point to numerous potential benefits with minimal on the downside.

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