Data out of France support a link between psoriasis disease activity and the consumption of ultraprocessed foods like soda and frozen pizza.

In the large NutriNet-Santé cohort, people with active psoriasis more frequently belonged to the top tertile of ultraprocessed food consumption compared with individuals who never had the chronic skin condition (adjusted OR 1.36, 95% CI 1.14-1.63, P<0.001 for trend).

And that was after adjustment for age, BMI, alcohol intake, and comorbidities, reported Emilie Sbidian, MD, PhD, of Hôpital Henri Mondor in Créteil, France, and colleagues in JAMA Dermatology.

“Processed foods, especially ultraprocessed foods, are bad for our health,” said Steven Daveluy, MD, of Wayne State University in Dearborn, Michigan, who was not involved in the research. “The association has been demonstrated for other diseases, but this is the first study for psoriasis.”

Daveluy highlighted the study’s implication that ultraprocessed food intake has a proinflammatory action separate from high BMI. “This means that the foods don’t just impact our bodies by increasing our weight and body fat. The foods themselves are triggering inflammation.”

“This is a really important concept when we consider food as medicine,” he told MedPage Today. “Some foods are healthy and help our immune system function and maintain balance. Other foods, especially ultraprocessed foods, trigger the immune system to cause inflammation.”

Notably, however, Sbidian and colleagues reported that they could not prove a statistically significant association between higher consumption of ultraprocessed foods and active psoriasis when they restricted psoriasis cases to those validated by a dermatologist (adjusted OR 1.32, 95% CI 1.06-1.64, P=0.13 for trend).

Additionally, the people with nonactive psoriasis could not be characterized as eating more or less of these foods compared with people who never had psoriasis.

“More large-scale studies are needed to investigate the role of [ultraprocessed food] intake in psoriasis onset,” the authors wrote.

“The more evidence the better,” Daveluy said. “Studies like this help provide the evidence that we need when we’re trying to inform lawmakers to make policies that are good for everyone’s health. These policies could involve education, like the food pyramid, policies that determine what foods are served in school cafeterias, and even regulations regarding the foods we put into our bodies.”

The French analysis relied on NutriNet-Santé, an ongoing observational cohort that has also been the basis of other observational research suggesting harm from artificial sweeteners and food additive emulsifiers.

Sbidian and colleagues’ study included 18,528 participants with data from November 2021 to June 2022. At inclusion, cohort participants had been asked to complete questionnaires regarding their diet, sociodemographic lifestyle, physical activity, anthropometric factors, and health status.

The researchers classified certain foods as processed or ultraprocessed and applied this to dietary records available from the cohort. Intake of the ultraprocessed food category was extrapolated from the proportion of these foods consumed by weight relative to total weight of food and beverages consumed per person.

Participants self-reported their psoriasis status as never-had (90%), nonactive (6%), or active (4%). The active psoriasis group had fewer women compared with participants in the never-had and nonactive groups (68% vs 74% and 75%, respectively) and more individuals with a BMI over 30 (16% vs 9% and 11%). Individuals with active psoriasis also had more prevalent comorbidities such as cardiovascular disease compared with the never-had group (7% vs 5%), diabetes (6% vs 4%), inflammatory bowel disease (2% vs 1%), and inflammatory rheumatism (9% vs 3%).

Sbidian and co-authors acknowledged the study’s potential underestimation of the link between active psoriasis and ultraprocessed food intake, given the relatively healthier cohort population compared with the French general population. Other limitations are the possible misclassification of psoriasis due to the study’s use of self-report, and the inability to ascertain causality due to the observational nature of the report.

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