There have been few RCTs assessing the effects of oral vitamin D supplementation on psoriasis so far, especially in Asia, and any such study has had inconclusive results.
As such, the researchers sought to investigate the clinical impact of oral vitamin D2 supplementation on psoriasis.
They recruited 45 psoriasis patients aged 18 to 70 for the trial, whose primary outcome was the improvement of the Psoriasis Area and Severity Index (PASI) score three and six months after treatment.
During the enrolment stage, the patients' mean PASI score was 4.45, and 26.7% of them were vitamin D-deficient.
For six months, 23 of the patients were randomly assigned to receive 60,00IU of vitamin D2 once every fortnight, while the rest were given similar-looking placebo pills at the same dosage and frequency.
At the same time, the researchers monitored their serum levels of 25(OH)D, calcium, phosphate, parathyroid hormone, C-reactive protein, and adverse events.
Subsequently, they reported that three months after treatment had begun, 34.21% of the patients who had been taking vitamin D2 saw significantly greater improvement in PASI, compared to 1.85% in the placebo group.
The intervention group also saw their mean serum 25(OH)D levels rise significantly, and these were inversely correlated with PASI scores during the six-month follow-up.
The researchers reported that there were no major adverse events observed throughout the study, and that oral vitamin D2 supplementation was a safe and efficacious way to increase serum vitamin D levels and improve treatment outcome in psoriasis patients.
Improvements and indications
However, they also said the small number of patients involved in the study might have been responsible for the significant improvements they observed after six months of treatment, and that the non-significant difference observed at this time could have linked to the mild degree of psoriasis severity in the study.
As such, the recommended including more cases of different disease severities with greater inflammation in future studies, as these "may be able to exhibit a statistically significant difference".
Still, they maintained that the inverse correlation between the severity of psoriasis and serum 25(OH)D concentrations was consistent with previous studies.
Vitamin D is known to have numerous clinical benefits, including the regulation of bone and calcium homeostasis, as well as immunomodulatory properties, thanks to an increasing amount of evidence regarding its positive effects on chronic inflammatory, autoimmune and infectious diseases.
In addition, there has been evidence of lower serum 25(OH)D concentrations and a higher prevalence of vitamin D deficiency in psoriatic patients. In this study, the patients' vitamin D deficiency at baseline was nearly five times higher than the prevalence of 5.7% among the general Thai population.
In conclusion, the study's authors wrote: "These findings suggest that psoriatic patients may be at risk of vitamin D deficiency. Some studies have shown associations between vitamin D-binding protein gene polymorphism and the risk of vitamin D deficiency, or vitamin-D receptor gene polymorphism and the degree of response to topical vitamin D analogues.
"The optimal dose of supplementation for inducing the immunomodulatory effect of vitamin D is still unknown and varies in many studies. We chose 60,000IU every two weeks, which equates to 4,285IU per day; this dose is within the 4,000 to 10,000IU/day that is well tolerated and recommended by the Institute of Medicine and Endocrine Society.
"Our study demonstrated improvement of mild psoriasis with oral vitamin D2 supplementation, an increase in serum 25(OH)D concentrations, a reduced rate of vitamin D deficiency, and good tolerability.
"Our data suggests vitamin D2 is a good adjunctive treatment to the standard therapy. Additional studies should examine the efficacy of higher doses and longer duration of vitamin D2 (supplementation) in moderately severe and severe psoriasis to determine whether vitamin D would be a suitable adjunct treatment."
Source: Dermatology Research and Practice
"The Clinical Effect of Oral Vitamin D2 Supplementation on Psoriasis: A Double-Blind, Randomized, Placebo-Controlled Study"
Authors: Wareeporn Disphanurat, et al.