Is the severity of psoriasis associated with the consumption of ultra-processed foods?

Biscuits, ready meals, dairy desserts. Ultra-processed foods have invaded our daily diet. According to INSERM, in 2024 they accounted for nearly one third of our daily caloric intake. However, while they appeal for their convenience and taste, their nutritional profile is lacking and raises concerns about health effects. Numerous studies have shown a link between a diet high in ultra-processed products and an increased risk of chronic diseases. Obesity, type 2 diabetes, cardiovascular diseases and even some cancers are associated with these products, which are low in nutrients and high in refined sugars and saturated fats—pro-inflammatory compounds. A recent study led by dermatologist Émilie SBIDIAN and her team suggests ultra-processed foods may play a role in psoriasis.

Researchers examined the profiles of 18,528 individuals aged over 15, enrolled in the NutriNet-Santé database between 2021 and 2022. Among them, 1,825 had psoriasis and 803 had an active form of the condition. Participants reported their daily intake of ultra-processed foods in milligrams (mg), data not disclosed in the study. Researchers adjusted analyses for age, alcohol consumption, body mass index (BMI), and other conditions. They formed three groups based on ultra-processed food intake: low, medium, and high. A correlation emerged between psoriasis and a diet high in ultra-processed foods.

People with active psoriasis had a 36% higher risk of being among the highest consumers of ultra-processed foods compared with those without psoriasis.

While the study does not establish a direct causal link, only a correlation, it opens new perspectives. The results appear to indicate that the association between psoriasis and the intake of ultra-processed foods is not limited to this skin condition’s impact on type 2 diabetes and cardiovascular disease. They suggest that additives and processing steps in these products play a potential role in worsening inflammation. Several studies have shown an association between ultra-processed food consumption and elevated levels of high-sensitivity C-reactive protein (hs-CRP) and tumor necrosis factor alpha (TNF-α), markers of inflammation.

One hypothesis concerns the high carbohydrate content of ultra-processed foods. After ingestion, these carbs trigger an insulin spike, a hormone known to promote pro-inflammatory processes. Insulin stimulates interleukin-6 (IL-6) production, a pro-inflammatory cytokine, and can also activate the insulin-like growth factor 1 (IGF-1) pathway, involved in keratinocyte proliferation. However, the psoriasis being a chronic inflammatory disease characterized by excessive keratinocyte proliferation and immune system activation, this phenomenon could contribute to a vicious cycle. A diet high in carbohydrates could sustain a persistent inflammatory state that may worsen psoriasis flares.

The study has several limitations, as the researchers state. First, psoriasis cases were self-reported, which may lead to misclassification. The cross-sectional design does not allow a causal relationship to be established: it is impossible to know whether the high consumption of ultra-processed foods precedes or follows flare-ups of psoriasis. Another limitation lies in the lack of detail regarding high or low intake of ultra-processed foods, making the results difficult to interpret.

To better understand the role of ultra-processed foods in the development of psoriasis, large-scale prospective studies remain necessary.

Though there is no single Mediterranean diet—each country has its own culinary traditions—Mediterranean cuisine has certain distinguishing features and is characterized by its emphasis on plant-based foods, such as fruits, vegetables, legumes, nuts, and seeds. Most health professionals agree the Mediterranean diet supports health and may help maintain cognitive function, promote cardiovascular health, and regulate blood glucose. It may offer a protective effect in psoriasis.

A study of 257 adults with psoriasis who completed an online survey showed an inverse correlation between adherence to a diet high in fruits and vegetables and the severity of psoriasis. In addition to answering questions about their diet, participants rated lesion severity using a scoring system considering the appearance of psoriasis, the symptoms experienced, and its psychological impact. Researchers then applied statistical adjustments to account for volunteers’ demographic characteristics as well as age, sex, smoking status, height, weight, current treatment, and any associated comorbidities.

The study’s main findings indicate that individuals with little or no adherence to a Mediterranean diet report more severe psoriasis.

However, these results should be qualified. The study relies on self-reported data for dietary habits and psoriasis severity. This methodology may introduce biases related to subjective symptom perception or imperfect dietary recall. Moreover, this is a cross-sectional survey rather than a long-term follow-up, which makes it difficult to establish a causal link between the Mediterranean diet and psoriasis symptoms. Large-scale, controlled clinical trials conducted over an extended period would help confirm or refute these observations.

How can these results be explained?

Several hypotheses may explain the Mediterranean diet’s possible protective effect on psoriasis severity. One of these is based on the anti-inflammatory action of its components. Fruits, vegetables, and oils in this diet are rich in polyphenols, compounds that can modulate inflammation by reducing IL-6 and CRP release. The unsaturated fatty acids abundant in this diet, including omega-3s from fatty fish and olive oil, play a key role in the regulation of immune responses. Studies show omega-3s can inhibit keratinocyte activation and limit immune cell infiltration in the skin, two processes involved in psoriasis plaque formation.

It is important to note that these effects were mainly observed in studies in vitro where the concentrations of omega-3 used were much higher than those achievable through typical dietary intake, even in omega-3–rich foods such as fatty fish or plant oils. In addition, in these foods, omega-3s rarely occur in isolation: they interact with other nutrients, such as antioxidants, proteins, or other fatty acids, which can modulate their bioavailability and effects. Therefore, it is difficult to conclude that omega-3 intake via dietary intake will produce the same effects as those observed in vitro. The most important factor remains maintain homeostasis in the body by following a balanced diet rich in diverse nutrients and adopting a healthy lifestyle that includes regular physical activity, which helps regulate inflammation and support overall health.

To confirm that dietary advice can play a role in managing psoriasis, the next step is to conduct a controlled clinical trial.