Vitamin D and its possible effects on chronic pains have long been a conundrum. We may have an answer! It reviewed published randomized controlled trials(RCTs).
The result is a bit inconclusive but not without interest
Inconclusive because of 19 RCTs reviewed, only 8 showed good effect on pain. That 8 concerned represents only one third of the total number of patients. The other limitation is that the articles published are widespread over the years between 1973 and 2015.
because for those patients that get a positive effect, it seems to be rather good
I have said it before on this site: Vitamin D serum levels must be done when facing chronic pain like fibromyalgia.
Supplementation cannot be the same for everyone: the darker the skin, the more supplementation is needed, the more exposure to the sun, the least the need for supplementation, the lesser the biological level the more is needed etc.
I would ask for a biological level and aim for a high one within safe limits. If after a month on this, the pain is not improved, I would still keep a small dose whilst searching for other means to decrease the pain as the cocktail effect could be beneficial.
First of all, it is very well done, trying to avoid as much as possible diverse bias and for that the authors must be congratulated.
Second, whilst it does not answer the query about Vitamin D and pain, it does open a can of limitations to such studies.
This is done by pairing two patients that have enough similarities such as gender, age, disease etc. One gets the treatment and the other one the placebo, still in a randomized double blind fashion. Unhappily, it is time consuming! But it is the ultimate way of getting a proper response.
We have been waiting too long and the usual way should be abandoned. The advent of IT and of being able to pair two patients that are in different countries should be helpful for that. If Google or Mark Zuckerberg of Facebook were to help whilst claiming that they are going to change our health this would be a good way. Pairing is superior to RCT.
This study points towards a fact. Vitamin D could help in chronic pain and should not be forgotten in the work-up.
Pain Physician. 2016 Sep-Oct;19(7):415-27.
Effect of Vitamin D Supplementation on Pain: A Systematic Review and Meta-analysis.
Wu Z1, Malihi Z1, Stewart AW1, Lawes CM1, Scragg R1.
There is conflicting evidence from previous qualitative reviews on the effect of vitamin D supplementation on pain.
To determine with quantitative methods if vitamin D supplementation lowers pain levels.
Quantitative meta-analysis of published randomized controlled trials (RCTs).
This meta-analysis examined all studies involving the effect of vitamin D supplementation on pain score.
Electronic sources (Medline, Embase, Cochrane Central Register of Controlled Trials, clinical trials website, and Google scholar) were systematically searched for RCTs of vitamin D supplementation and pain from inception of each database to October 2015.
Nineteen RCTs with 3,436 participants (1,780 on vitamin D supplementation and 1,656 on placebo) were included in the meta-analysis. For the primary outcome (mean change in pain score from baseline to final follow-up), 8 trials with 1,222 participants on vitamin D and 1,235 on placebo reported a significantly greater mean decrease in pain score for the vitamin D group compared to placebo (mean difference -0.57, 95% CI: -1.00 to -0.15, P = 0.007). The effect from vitamin D was greater in patients recruited with pre-existing pain (P-value for interaction = 0.03). Fourteen studies (1,548 on vitamin D, 1,430 on placebo) reported the mean pain score at final follow-up outcome, and no statistical difference was observed (mean difference -0.06, 95%CI: -0.44 to 0.33, P = 0.78). In 4 studies which reported pain improvement (209 on vitamin D, 146 on placebo), the effect size although not significant, shows participants in the vitamin D supplementation group were more likely to report pain improvement compared with the placebo group (relative risk 1.38, 95%CI: 0.93 to 2.05, P = 0.11).
Only a few studies reported the mean score change from baseline to final follow-up, and we do not have enough data to determine any modifying effect of baseline vitamin D status and different doses of vitamin D supplementation on pain.
A significantly greater mean decrease in pain score (primary outcome) was observed with vitamin D supplementation compared with placebo in people with chronic pain. These results suggest that vitamin D supplementation could have a role in the management of chronic pain.
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