Abstract: Psoriasis is an autoimmune and inflammatory skin disease. Psoriatic patients express
higher levels of plasma homocysteine (Hcy) concentration and pro-inflammatory mediators than
healthy people; this is frequently associated with vitamin D deficiency. The aim of this clinical study
was to investigate the effects of high doses of vitamin D supplementation on the parameters of Hcy
metabolism and cytokines in sera of psoriatic patients. This prospective study was conducted on
40 psoriatic patients who had the vitamin D deficiency. All patients received vitamin D 5000 IU/day
for three months. Clinical and biochemical measurements were taken at baseline and at follow up
(3 months). The results showed that the severity of clinical features, measured by the psoriasis area
severity index (PASI) score, were considerably improved in patients after vitamin D supplementation.
After vitamin D supplementation, most of the patients (n = 25 or 62.5%) had mild clinical form
(p < 0.001). After twelve weeks of intervention period, there were significant increases in vitamin
D and B12 serum levels in comparison to the levels that had been measured at the beginning
of the study (56.77 ± 14.66 nmol/L and 301.08 ± 95.02 pg/mL vs. 103.85 ± 32.20 nmol/L and
362.81 ± 118.56 pg/mL, respectively; p < 0.001). Moreover, serum levels of Hcy and folate were
significantly lower at the end of the study in comparison with the initial levels (12.45 ± 1.92 µmol/L
and 8.01 ± 3.88 mg/mL vs. 10.38 ± 1.66 µmol/L and 6.27 ± 2.60 mg/mL, respectively). High doses of
vitamin D supplementation led to a significant decrease in pro-inflammatory cytokines (IFN-7, TNF-α,
IL-1β, IL-6, IL-8, and IL-17) and high-sensitivity C-reactive protein (hsCRP), whereas the production
of anti-inflammatory cytokines (IL-10, IL-5) was up-regulated. In conclusion, supplementation with
high doses of vitamin D could be one of the possible preventive and therapeutic measures to reduce
systemic inflammation in psoriatic patients.