Psoriasis: Mediterranean diet may slow disease progression

A new study suggests that adhering to a Mediterranean diet may relieve the severity of psoriasis and slow its progression.

Psoriasis is a chronic inflammatory disease that affects about 6.7 million adults in the United States, according to recent estimates.

Some studies have shown that people with psoriasis are more prone to obesity and metabolic syndrome, and some have suggested that inflammation may be the reason behind this link.

Diet can play a key role in inflammatory conditions. Research has shown that pro-inflammatory compounds including saturated fats can worsen conditions such as inflammatory bowel disease and rheumatoid arthritis.

So, researchers led by Dr. Céline Phan — at the Hôpital Mondor in Créteil, France — set out to investigate whether conversely, an anti-inflammatory diet would have appeasing effects on symptoms of psoriasis.

The Mediterranean diet is considered anti-inflammatory because it has been associated with a lower incidence of chronic inflammatory illness.

Its high content of monounsaturated fats (which are found in olive oil and other plant oils), high levels of antioxidants and polyphenols (found in fruits and vegetables), and high content of fiber (from vegetables or wholegrain cereals) may all be responsible for the diet's anti-inflammatory properties.

Also, a Mediterranean diet limits dairy and meat consumption, as well as restricts alcohol use to a moderate level.

Dr. Phan and her colleagues studied the associations between adherence to the Mediterranean diet and the severity of psoriasis symptoms. Their findings were published in the journal JAMA Dermatology.

Mediterranean diet may reduce symptoms

The researchers analyzed the answers of 35,735 people who participated in a web-based questionnaire called NutriNet-Santé. Of those people, 3,557 had psoriasis. Symptoms were self-assessed as severe by 878 of them.

The dietary practices of the respondents were assessed using a MEDI-LITE score ranging from 0 (no adherence) to 18 (maximum adherence).

The researchers found that psoriasis severity correlated inversely with adherence to the Mediterranean diet. In other words, "Patients with severe psoriasis displayed low levels of adherence to the Mediterranean diet," write the authors.

Dr. Phan and colleagues explain:

"[T]his finding supports the hypothesis that the Mediterranean diet may slow the progression of psoriasis. If these findings are confirmed, adherence to a Mediterranean diet should be integrated into the routine management of moderate to severe psoriasis."

Strengths and limitations of the study

Dr. Phan and colleagues also note some strengths and limitations to their research. Firstly, the study sample used in the NutriNet-Santé questionnaire was extensive, which strengthens the results, and the dietary intake was assessed highly accurately by using a minimum of three food surveys.

However, the participants were all volunteers, which makes the results less generalizable to the wider population. People who would volunteer for medical research are presumably more worried about their health than the general population.

Finally, because the study was observational, it cannot establish causality. "Further prospective observational studies and randomized clinical trials are needed to confirm these results," write the researchers, "and experimental data are needed to establish the mechanistic links between psoriasis and diet."

"If these findings are confirmed," they conclude, "an optimized diet should be part of the multidisciplinary management of moderate to severe psoriasis, with a view to increasing therapeutic effectiveness."