The effect of vitamin D supplementation on pain: an analysis of data from the D-Health randomized controlled trial

Observational studies suggest that 25-hydroxy vitamin D (25(OH)D) concentration is inversely associated with pain. However, findings from intervention trials are inconsistent. We assessed the effect of vitamin D supplementation on pain using data from a large, double-blind, population-based, placebo-controlled trial (the D-Health Trial). 21,315 participants (aged 60-84 years) were randomly assigned to a monthly dose of 60,000 IU vitamin D3 or a matching placebo. Pain was measured using the 6-item Pain Impact Questionnaire (PIQ-6), administered 1, 2 and 5 years after enrollment. We used regression models (linear for continuous PIQ-6 score and log-binomial for binary categorizations of the score, namely 'some or more pain impact' and 'presence of any bodily pain') to estimate the effect of vitamin D on pain. We included 20,423 participants who completed ≥1 PIQ-6. In blood samples collected from 3943 randomly selected participants (∼800 per year) the mean (SD) 25(OH)D concentrations were 77 (SD 25) and 115 (SD 30) nmol/L in the placebo and vitamin D groups, respectively. Most (76%) participants were predicted to have 25(OH)D concentration >50 nmol/L at baseline. The mean PIQ-6 was similar in all surveys (∼50.4). The adjusted mean difference in PIQ-6 score (vitamin D cf placebo) was 0.02 (95% CI, -0.20 to 0.25). The proportion of participants with some or more pain impact and with presence of bodily pain was also similar between groups (both prevalence ratios 1.01, 95% CI 0.99 to 1.03). In conclusion, supplementation with 60,000 IU of vitamin D3 per month had negligible effect on bodily pain.