Chronic pain is categorized as pain in the body that lasts over three months. Anywhere from 10%-55% of individuals suffer from chronic pain throughout the world. This condition is often debilitating, negatively impacting an individual’s quality of life. In fact, people with chronic pain experience an increased risk for developing depression, anxiety and insomnia.
With the etiology of chronic pain remaining unclear, it has proven to be a challenging condition to treat. Approximately 3 billion dollars in health care costs are spent every year for pain management; yet, current treatments are often found to be unsuccessful. Furthermore, chronic pain is a leading cause of disability, resulting in a financial burden of lost productive work.
Researchers hypothesize that vitamin D influences pain manifestations through its anti-inflammatory and immune regulatory properties. Past research suggests that vitamin D deficiency may contribute to the onset of chronic pain. Another study found vitamin D status may be linked with pain sensitivity. RCTs have evaluated this topic as well; however, past literature reviews of RCTs have produced inconsistent findings. It is believed that the use of qualitative data may have been the source of these conflicting results. Therefore, researchers conducted a quantitative systematic review and meta-analysis of RCTs to evaluate the effect of vitamin D supplementation on pain scores in individuals with chronic pain.
RCTs were included in the analysis if they used a vitamin D treatment and placebo group, reported pain outcomes, had a minimum of 4 week follow up and enrolled participants at least 18 years of age. A total of 19 RCTs with 3,436 participants matched this inclusion criterion. Of the participants, 1,780 supplemented with vitamin D and 1,656 were given a placebo pill. The researchers evaluated the patients’ vitamin D levels and pain scores at baseline and follow up. A total of 8 trials reported change in pain scores as a primary outcome.
Here is what they found:
- A significant decrease in pain score was observed in the vitamin D supplementation group (n = 1,222) compared to the placebo group (n = 1,235; p = 0.007) in the 8 trials that reported the mean change in pain score as a primary outcome from baseline to follow-up.
- A total of 4 studies observed pain improvement as a secondary outcome; though, this did not reach statistical significance (RR 1.38, p = 0.11).
- In a subgroup analysis, those who were hospitalized with pain related medical conditions experienced a decrease in pain from vitamin D supplementation (p = 0.01).
- The studies that used surveys recruited from the community or focused on vitamin D status did not observe a change in non-specific widespread pain in the vitamin D supplementation group (p = 0.29).
- When comparing short term (< 6 months) and long term (> 6 months) supplementation, there was no change in outcome (p = 0.81).
- A total of 14 studies reported the mean pain score at final follow-up, showing no statistical difference in pain upon completion of the study (p = 0.78); though, the researchers observed heterogeneity in this secondary outcome (p = 0.001).
The researchers concluded,
“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.”
The researchers discussed a plausible explanation for the lack of significant findings between vitamin D supplementation and pain reduction in the community based studies. With only two studies evaluating chronic pain among the community, and one of these providing their participants with a meager 400 IU/d, these findings are expected to be inconclusive.
As always, it is important to note the study’s limitations. There were a variety of assessment tools used between studies, and not all of the studies assessed the change in pain score from the baseline to completion of the study. In an effort to standardize this, the researchers may have introduced heterogeneity in the study. Heterogeneity occurs in meta-analyses when the observed intervention effect shows more variation than one would expect due to random chance. There was also a lack of data to evaluate the effect of vitamin D status and different doses of vitamin D supplementation on pain.
This meta-analysis evaluated primarily low dose trials, and yet they showed an effect on pain. We wonder what the results would be, if 5,000 or 10,000 IU/day were given. If vitamin D has helped your pain, please email us at [email protected]
The researchers added,
“Further well-designed placebo controlled long term trials should be conducted to confirm these findings.”
Sturges, M. & Cannell, JJ. Vitamin D supplementation decreases pain scores in those with chronic pain, according to new study. The Vitamin D Council Blog & Newsletter, 2016.