The latest “study” on vitamin D reached the conclusion that vitamin D does nothing to prevent myriad medical conditions. You may be wondering why I placed study in quotation marks. That’s because it’s not actually a new study. It’s an analysis of the results from a number of randomized controlled trials of vitamin D supplements.
Of course, there are the usual issues with meta-analyses. We don’t know for certain if the authors cherry-picked the studies they chose to look at. We don’t know (without spending substantial amounts of our own time, and probably money) if the original studies were flawed. It’s a good thing that it’s good that this analysis looked at studies using a randomized control model. This avoids the obvious potential confounding factors seen with observational studies. However, I have some doubts that these studies would have been conducted over long enough time-spans to accurately assess the use of vitamin D supplements. After all, they were looking at the effects of vitamin D supplementation on myocardial infarction or ischaemic heart disease, stroke or cerebrovascular disease, cancer, total fracture, hip fracture, and mortality. To truly determine the effects of vitamin D supplementation on these conditions supplementation would have had to begin in childhood and continue until death (or at least very old age).
The authors found that vitamin D did not affect outcomes by more than 15% for any of the above conditions, aside from hip fractures in institutionalized seniors.
I’m inclined to think that we may be expecting far too much from vitamins and minerals. Just because vitamin D probably doesn’t prevent cancer or heart disease doesn’t mean that there aren’t any benefits to be obtained from taking it as a supplement. Perhaps it may prove to be beneficial in mood regulation, cold prevention, or something else less earth shattering than these studies looked at.
Perhaps there is no benefit to taking vitamin D supplements. However, I’m not quite ready to toss my bottle. I know that I can’t meet the currently recommended amount of vitamin D through diet alone. And I’m certainly not getting any from sun exposure this time of year. I don’t think that we should dispose of the current vitamin D recommendations on the basis of one meta-analysis. I’m certainly open to changing my mind but for now I’d like to hedge my bets. I’d rather risk taking a “useless” vitamin D supplement than risk experiencing adverse health consequences from not consuming sufficient vitamin D.
In addition, I worry that research such as this may lead to new parents neglecting to supplement their infants with vitamin D and causing a resurgence in rickets. Just because there’s uncertainty about the long-term outcomes of vitamin D supplementation doesn’t mean that we don’t know the benefits in early childhood.