Vitamin D and Psoriasis: What's the Connection?

meta-analysis PMID: 37571324

Quick Summary: Research shows people with psoriasis often have low vitamin D levels. Taking vitamin D supplements might help improve psoriasis symptoms.

Vitamin D Deficiency and Psoriasis: What's the Link?

This study looked at many previous studies to see how vitamin D and psoriasis are connected. They found that people with psoriasis, a skin condition causing red, itchy patches, often have lower levels of vitamin D in their blood compared to people without psoriasis.

Study Details

Who was studied: The researchers looked at data from 23 different studies. These studies included a total of 1,876 people with psoriasis and 7,532 people without psoriasis (controls).

How long: The study analyzed existing research, so there wasn't a set "duration" like in a typical study. The research they looked at varied in length.

What they took: Some studies looked at people taking vitamin D supplements. The exact dose varied between studies, but it was taken orally (by mouth).

What This Means For You

Get Tested: If you have psoriasis, talk to your doctor about getting your vitamin D levels checked.

Consider Supplementation: If your vitamin D levels are low, your doctor may recommend taking a vitamin D supplement. This could potentially help improve your psoriasis symptoms.

Not a Cure-All: Vitamin D supplements may help, but they are not a cure for psoriasis. They may be used in conjunction with other treatments.

Talk to Your Doctor: Always discuss any new supplements with your doctor to make sure they are safe for you.

Study Limitations

Dose Differences: The study didn't specify the exact amount of vitamin D people took in the different studies.

Not a Cause: The study shows a link, but it doesn't prove that low vitamin D causes psoriasis to be worse. It could be that people with more severe psoriasis have lower vitamin D levels.

More Research Needed: More research is needed to figure out the best vitamin D dose and how it works to help with psoriasis.

Key Findings

This meta-analysis found that psoriasis patients had significantly lower serum 25-hydroxyvitamin D (25(OH)D) levels compared to controls (21.0 ± 8.3 vs. 27.3 ± 9.8 ng/mL, p < 0.001). Oral vitamin D supplementation demonstrated a moderate but statistically significant improvement in Psoriasis Area and Severity Index (PASI) scores (unstandardized mean difference [UMD] -3.8, 95% CI -6.3 to -1.3, p = 0.002). Subgroup analysis suggested greater efficacy in patients with severe psoriasis or baseline vitamin D deficiency.

Study Design

The study is a systematic review and meta-analysis of observational and interventional research. Researchers analyzed 23 studies (1876 psoriasis patients, 7532 controls) from online databases up to July 2023. Risk of bias was assessed using the Cochrane Collaboration tool for RCTs and the Newcastle-Ottawa scale for case-control studies. The design included two arms: (1) comparing serum 25(OH)D levels between groups and (2) evaluating the efficacy of vitamin D supplementation in RCTs.

Dosage & Administration

The summary did not specify exact vitamin D dosages used in the included RCTs. However, supplementation protocols involved oral administration (likely varying doses and durations). The lack of detailed dosing information limits interpretation of optimal therapeutic regimens.

Results & Efficacy

Psoriasis patients showed a large, significant deficit in 25(OH)D levels (UMD -6.3 ng/mL, 95% CI -8.0 to -4.6, p < 0.001). Oral vitamin D supplementation reduced PASI scores by 3.8 points compared to controls (UMD -3.8, 95% CI -6.3 to -1.3, p = 0.002). Heterogeneity was high across studies (I² not reported), suggesting variability in patient populations, dosing strategies, or study quality.

Limitations

Dosing ambiguity: Specific vitamin D doses, formulations (e.g., D3 vs. D2), and treatment durations were not detailed in the abstract.
Observational data: Lower 25(OH)D levels in psoriasis patients may reflect disease activity rather than causation.
Heterogeneity: Differences in study design, patient demographics, and supplementation protocols may affect result consistency.
Publication bias: Smaller studies with null results might be underrepresented.
Unreported adverse effects: Safety data on supplementation were not summarized.

Clinical Relevance

The findings suggest that vitamin D deficiency may contribute to psoriasis pathogenesis, and correcting this deficiency could improve symptoms. However, the lack of standardized dosing limits direct application. Supplement users with psoriasis should consider:
- Testing 25(OH)D levels: Deficiency (<20 ng/mL) may warrant supplementation.
- Individualized dosing: Clinicians should tailor doses based on baseline levels and disease severity.
- Adjunctive therapy: Vitamin D may support conventional treatments but should not replace them.
Further research is needed to define optimal dosing, long-term safety, and mechanisms linking vitamin D to psoriasis.

Note: The study’s abstract does not specify patient demographics (e.g., age, ethnicity, geographic location), which could influence vitamin D metabolism and psoriasis severity. Always consult a healthcare provider before starting supplementation.