Adherence to a Mediterranean diet that is high in anti-inflammatory nutrients may lessen the severity of psoriasis, according to a study published online July 25 in JAMA Dermatology.
"We found an association between the Mediterranean diet and the severity of psoriasis. We believe that a healthy diet could improve the severity of psoriasis," said the study’s corresponding author Emilie Sbidian, M.D., Ph.D., of Mondor Hospital in Paris.
Generally, she said, having a healthy diet benefits everyone, especially patients with psoriasis and other inflammatory disorders. "The key point for the Mediterranean diet is a high proportion of fruits and vegetables and extra-virgin olive oil."
Monounsaturated fats and vitamin D may reduce the severity of psoriasis because they are anti-inflammatory nutrients. Conversely, the Mediterranean includes low to moderate amounts of proinflammatory nutrients such as meat, dairy products, eggs and alcohol, although it is not the only diet that has been associated with lowering the severity of psoriasis.
The study included 35,735 patients of which 2.2% had psoriasis, 878 had severe psoriasis, and 299 patients reported incident cases or psoriasis.
The patients participated in an online survey. Investigators assessed their average daily consumption of fruit, vegetables, legumes, meat, fish, cereals, olive oil and dairy products, as well as certain vitamins and supplements, fiber, carbohydrates, omega-3 and omega-6 fatty acids and alcohol. Other factors that were considered included sociodemographic and lifestyle factors, health status, diet and exercise.
Patients reported their dietary intake through a series of three nonconsecutive, validated, web-based 24-hour dietary records, randomly assigned over a two-week period for six months. Food consumption was recorded with MEDI-LITE. MEDI-LITE scores ranged from zero to 18 and were based on the average of three to 15 dietary records gathered during a patient's first two years after study inclusion.
The analysis showed that patients with severe psoriasis were significantly more likely to have a MEDI-LITE score in the lowest tertile (zero through seven) with 339 patients (46 percent) scored in this tertile, signifying low adherence to the Mediterranean diet (p<0.0001). The corresponding figures for patients with no severe psoriasis and no psoriasis were 36 percent each. Investigators also found significant associations between severe psoriasis and female gender (which accounted for 76.9 percent of the severe psoriasis subgroup), body mass index above 30 (15.3 percent), non-smoking status (43.2 percent), cardiovascular disease, arterial hypertension, diabetes, hypertriglyceridemia and depression.
Multivariate analysis, adjusted for the patient-related covariates listed above, revealed a significant inverse relationship between MEDI-LITE scores and psoriasis severity. Sensitivity analyses showed similar patterns, whether psoriasis was diagnosed by a physician or a dermatologist specifically, as well as when researchers analyzed only patients with a history of hospitalization and/or systemic therapy. Multivariate analysis of the 299 incident psoriasis cases revealed odds ratios similar to those of the entire population.
This was an observational study with strengths including its large sample size and the quality of the nutrition reporting, which was validated in other studies. After participants answer detailed questions about the types and quantities of foods they have eaten, Dr. Sbidian explained, a nutritionist breaks down the reported foods into specific nutrients.
"And we performed many sensitivity analyses, so we are confident in our results." Even after adjusting for variables that relate to psoriasis severity, such as age, obesity, depression and cardiovascular disease, the impact of the Mediterranean diet on psoriasis severity persisted.
The small number of incident psoriasis cases uncovered makes it impossible to determine the relationship between the Mediterranean diet and new cases of psoriasis, she said. Repeating the study in around two years may provide insight here, Dr. Sbidian added.
Celine Phan MD, Mathilde Touvier PhD, Emmanuelle Kesse-Guyot PhD, et al. "Association Between Mediterranean Anti-Inflammatory Dietary Profile and Severity of Psoriasis: Results from the NutriNet-Santé Cohort," JAMA Dermatology. July 2018