The relationship between vitamin D and psoriasis is complex and involves multiple functions that help control disease symptoms, the authors explain.
In a nutshell, 25-hydroxy vitamin D downregulates the expression and production of several pro-inflammatory cytokines, “thereby establishing its anti-inflammatory effect on the inflammatory profile of psoriasis”.
“Low concentration of 25-hydroxy vitamin D promotes keratinocyte proliferation and maturation while at higher concentration has an inhibitory effect,” they say.
This activity is strongly supported by comprehensive meta-analysis, including clinical trials, and having observed efficacy and modulatory activity in the current trial, the authors advocate early detection to improve clinical outcomes for patients.
“As per previous studies, oral vitamin D supplementation could decrease psoriasis-related comorbidity and could be used as a treatment option in psoriatic patients.”
Vitamin D is a fat-soluble steroid hormone associated with calcium homeostasis and synthesis of antimicrobial peptides. It also plays an important role in the pathogenesis of different skin diseases, including psoriasis, by inhibiting T-cell proliferation.
The most common clinical variant is Psoriasis Vulgaris, characterised by erythematous lesions with scaly appearance that generally effect the scalp, knees, sacral spine region and elbows.
Prevalence varies by region but is highest in high-income countries, affecting around 1.5% of individuals in western Europe, compared to 0.1% in east Asia.
The disease is triggered by a combination of genetic, environmental, social, and other random factors, including diet, and research suggests higher incidence among men.
As a general rule, patients with psoriasis are more than twice as likely to be smokers, and severity is linked to heavy smoking. Similarly, studies report a positive correlation between alcohol intake and “extent of psoriasis”.
“Alcohol may affect psoriasis through several mechanisms, such as increased susceptibility to infections, stimulation of lymphocyte and keratinocyte proliferation, and production of pro-inflammatory cytokines,” the authors’ comment.
Furthermore, there is strong genetic link to psoriasis incidence. “A large number of genetic loci have been described in psoriasis in the last decade by the genome-wide association studies,” they say.
Two hundred and eighty-five patients were enrolled in the two-year study, along with 317 healthy controls. Subjects were aged 18 years and over and matched with respect to age and gender.
Degree of psoriasis in patients was determined by the Psoriasis Area Severity Index (PASI) score. All subjects were exposed to sunlight on the face and forearms for at least 20 to 30 minutes at midday, two to three times per week, in addition to daily dietary intake of 25-hydroxy vitamin D.
Blood samples were collected to test vitamin D levels and statistical analysis used to compare levels in relation to age, sex, smoking status, for example, between the two groups.
Approximately 11.6% of psoriasis patients had a family history of the disease, and 31.9% a history of alcohol abuse.
A significant proportion of psoriasis patients were found deficient in 25-hydroxy vitamin D, compared to healthy controls.
Of the test subjects, serum vitamin D was insufficient for 28.4% of the cohort and 30.9% were deficient, whereas 82% of the control registered sufficient levels and none were deficient.
Equally, the frequency of insufficient and deficient levels was considerably higher in psoriasis patients, compared to controls, for both men and women.
Low vitamin D was significantly associated with risk of developing psoriasis, irrespective of age or smoking status, although smokers had a “many fold higher” risk of developing psoriasis due to deficiency, compared to non-smokers.
Psoriasis patients with low vitamin D also displayed patterns of alcohol abuse, hypertension, chronic medication, nail changes, and duration of symptoms.
The data shows 25-hydroxy vitamin D deficiency is common in severe forms of psoriasis, therefore “maintenance of levels above 30 ng/ml could contribute to a better evolution when it comes to autoimmune and inflammatory diseases”, the authors assert.
Supplementation did not improve symptoms in psoriatic patients with normal serum 25-hydroxy vitamin D levels.
Source: BMC Nutrition
Published online, October 19, 2022: http://doi.org/10.1186/s40795-022-00610-y
‘Vitamin D status in Psoriasis: impact and clinical correlations’
Authors: G. Hassan Bhat, et al.