Can an Anti-Inflammatory Diet with Olive Oil Actually Treat Psoriasis?

Psoriasis is not a minor cosmetic inconvenience. It is a chronic, systemic immune-mediated disease affecting approximately 125 million people globally — about 2-3% of the world's population. Its hallmark: painful, scaly, inflamed plaques that appear on the skin when the immune system mistakenly attacks healthy tissue, causing keratinocytes (skin cells) to multiply at 10 times their normal rate.

For decades, treatment followed a predictable escalation ladder: moisturisers, then corticosteroid creams, then phototherapy, then systemic drugs like methotrexate, and — for the most severe cases — biologic agents that cost upwards of £20,000–$30,000 per patient per year. These biologics are extraordinarily effective, but they also suppress the entire immune system, carrying risks of serious infection, tuberculosis reactivation, and in some cases lymphoma.

What has received far less attention — despite compelling epidemiological signals — is whether diet itself could meaningfully treat psoriasis. Observational studies have long noted that Mediterranean populations have lower psoriasis prevalence. Psoriasis patients who adhere closely to Mediterranean dietary patterns consistently report milder disease severity. But correlation is the entry ticket to science, not the conclusion.

In February 2024, a team of dermatologists and nutrition scientists in Madrid, Spain, enrolled their first patient in a randomized controlled trial designed to change that. The MEDIPSO trial — Impact of the Mediterranean Diet on Patients With Psoriasis — would run for 16 weeks and be published in one of dermatology's most prestigious journals. The results were striking enough to warrant this commentary.

Extra virgin olive oil was not a side player in this trial. It was a weekly provision given directly to the intervention group — the fat source that anchors the Mediterranean dietary pattern, the vehicle for hundreds of bioactive polyphenols, and the substance we examine in this commentary.

The MEDIPSO trial screened 45 individuals and enrolled 38 adults with clinically confirmed mild-to-moderate psoriasis, defined as a Psoriasis Area and Severity Index (PASI) score between 2 and 10. Participants were already receiving stable topical therapy — corticosteroids, vitamin D analogues, or emollients — and continued that treatment throughout the trial. The study ran from February 2024 to March 2025. Of the 38 enrolled, 37 completed the trial (97.4% retention — exceptionally high for a dietary intervention study).

Participants were randomized 1:1 to two arms:

The primary outcome was the change in PASI score from baseline to week 16. The PASI (Psoriasis Area and Severity Index) is the gold standard measure of psoriasis severity used in virtually every major clinical drug trial — it quantifies the extent and severity of redness, scaling, and plaque thickness across four body regions, generating a score from 0 (clear skin) to 72 (maximum disease). A score of 2-10 indicates mild-to-moderate disease.

Secondary outcomes included: Mediterranean diet adherence score, anthropometric and metabolic parameters (weight, waist circumference, blood pressure, lipids, glucose, HbA1c), serum inflammatory cytokines (IL-17, IL-22, TNF-α), and patient-reported outcomes including the Dermatology Life Quality Index (DLQI) and the Hospital Anxiety and Depression Scale (HADS).

Critically, the evaluators — the dermatologists who assessed PASI scores — were blinded to group allocation. While the patients themselves couldn't be blinded (they knew what they were eating), the clinicians conducting the primary outcome assessment did not know which arm each patient was in. This is the strongest feasible design for a dietary intervention trial and protects against assessor bias on the primary outcome.

The results were not subtle. The Mediterranean diet group experienced a substantial improvement in psoriasis severity; the control group did not. The between-group gap was statistically overwhelming.

The researchers also observed improvements in Mediterranean diet adherence scores (confirming the intervention worked), and trends toward improvement in inflammatory cytokines and patient-reported quality of life — though the sample size limited statistical power for secondary endpoints.

To understand why olive oil might work against psoriasis, you need to understand what causes psoriasis at the molecular level. And when you do, the rationale for EVOO becomes almost obvious.

Psoriasis is driven primarily by the Th17/IL-17 immune axis. Dysregulated T-helper 17 cells release interleukin-17A (IL-17A), which causes keratinocytes (skin cells) to hyperproliferate and release additional cytokines including TNF-α, IL-6, and IL-1β. This creates a self-amplifying inflammatory loop — plaques form, they recruit more immune cells, which release more cytokines, which create more plaques. At the centre of this loop sits NF-κB — the master transcription factor of inflammation.

The MEDIPSO trial did not emerge from a vacuum. It is the first properly powered RCT to confirm what a growing body of observational and pilot data has suggested for years.

The MEDIPSO trial is the best evidence we have to date — but it has real limitations that scientific honesty demands we name.

Not a paradigm shift yet — but a landmark data point that no serious dermatologist should ignore.

Here is what makes this trial stand out from the noise of nutritional research:

The PASI 75 finding is genuinely extraordinary. Zero patients in the control group achieved PASI 75. Nearly half in the Mediterranean diet group did. In a population receiving stable topical therapy — meaning the control group was already getting standard-of-care treatment — that outcome gap is remarkable. In pharmaceutical terms, the number needed to treat (NNT) would be approximately 2 for the dietary intervention. For context, the NNT for common antidepressants is typically 5-10; statin therapy to prevent one myocardial infarction over 5 years is 20-30. An NNT of 2 for a dietary change in a chronic disease — if it holds up in larger trials — would be extraordinary.

The publication venue matters. JAMA Dermatology is not a fringe journal. It requires rigorous peer review, has an impact factor placing it among the top dermatology publications globally, and is read by practicing dermatologists who make prescribing decisions. When a study of this type clears that bar, it has weight.

The mechanism is coherent and well-supported. This isn't a “we observed an effect without any mechanistic understanding” situation. The anti-inflammatory pathways of EVOO polyphenols — COX inhibition, NF-κB suppression, ROS quenching — align precisely with the known pathophysiology of psoriasis. The HbA1c improvement connects to the well-established psoriasis-metabolic syndrome comorbidity. The story hangs together.

The risk-benefit calculation is almost unambiguously positive. High-polyphenol EVOO consumed daily as part of a Mediterranean pattern has documented cardiovascular benefits (PREDIMED), neuroprotective effects (Harvard 28-year cohort), anti-cancer properties (oleocanthal), and now — anti-psoriatic effects. The “side effects” of adopting this diet include lower blood pressure, improved lipid profiles, better blood sugar control, and reduced dementia risk. The “cost” is approximately £5-15 more per week in food expenditure. The downside scenario of trying this intervention is essentially “you eat a healthier diet for 16 weeks with no skin improvement” — a scenario most people would still consider a net positive.