A recent study published in JAMA Dermatology has drawn attention. Reported by Vijay Kumar Malesu and reviewed by Benedette Cuffari, M.Sc., the study delved deeply into the association between the intake of ultra-processed foods (UPF) and the status of active psoriasis, providing new evidence for the crucial role of diet in managing this chronic skin disease.
Psoriasis is a chronic inflammatory skin disease caused by a combination of genetic, immune, and environmental factors. Among them, diet – especially foods rich in pro-inflammatory or anti-inflammatory components – has been recognized as a key modifiable factor that affects the level of inflammation and the quality of life of patients with inflammatory diseases. Ultra-processed foods are characterized by high levels of added sugars, fats, and artificial additives, and have previously been linked to various health problems such as obesity, cardiovascular disease, and type 2 diabetes, which share inflammatory pathways with psoriasis. Although there are frequent signs of association, the specific role of UPF in the development of psoriasis remains unclear, and further research is urgently needed to uncover the mystery.
The research team adopted a cross-sectional analysis method, relying on data from the NutriNet-Santé cohort collected between November 29, 2021, and June 6, 2022. Participants aged 15 and older were included and divided into three groups according to their self-reported psoriasis status: never had psoriasis, non-active psoriasis, and active psoriasis.
The intake of UPF was evaluated through dietary records, with the daily consumption of UPF accurately quantified in grams, and the participants were classified into three tertiles according to their intake levels from low to high. Meanwhile, information on demographic, lifestyle, and clinical variables was widely collected, covering age, sex, educational level, body mass index (BMI), smoking status, physical activity, alcohol consumption, as well as comorbidities such as depression, diabetes, and cardiovascular disease.
Multinomial logistic regression models were used to evaluate the association between UPF intake and the status of psoriasis. To minimize bias, potential confounding factors, including sociodemographic factors, BMI, and comorbid conditions, were carefully adjusted. Sensitivity analyses were also carried out, including cases diagnosed by dermatologists and models excluding missing data, to ensure the accuracy of the research results. Statistical significance was determined by two-sided tests, and a P-value less than 0.05 was considered statistically significant. The data analysis was performed using SAS version 9.4. The entire study obtained ethical approval from the Institutional Review Board of the French Institute of Health and Medical Research, and all participants signed electronic informed consent forms.
A total of 18,528 participants were included in this study, with a median age of 62 years and 74% being female. Ten percent of the study cohort reported having psoriasis, with 4% and 6% of the cases classified as active and non-active, respectively.
The proportion of females in the active psoriasis group was 68%, lower than 75% in the non-active group and 74% in the group that had never had psoriasis. The prevalence of obesity among patients with active psoriasis was 16%, higher than 11% in the non-active group and 9% in the group that had never had psoriasis. Compared with those without a history of psoriasis (42%), the reporting rates of high-intensity physical activities were lower among patients with active and non-active psoriasis, at 38% and 39% respectively.
Comorbidities were more common among patients with active psoriasis than among those who had never had psoriasis. For example, the reporting rate of cardiovascular disease was 7% among patients with active psoriasis, while it was only 5% in the group that had never had psoriasis. The prevalence rates of diabetes and inflammatory rheumatism in the active group were 6% and 9% respectively, while in the group that had never had psoriasis, they were 4% and 3% respectively.
The unadjusted analysis showed a significant difference in UPF intake, with higher intake reported among patients with active psoriasis. After adjusting for confounding factors, participants in the highest tertile of UPF intake were 36% more likely to have active psoriasis than those in the lowest tertile. The results of the sensitivity analyses were consistent with this, but these associations were not statistically significant in the analysis of psoriasis cases diagnosed by dermatologists.
Further analysis indicated that the association between UPF intake and active psoriasis remained significant after taking BMI into account, which means that UPF intake has an independent impact on the activity of psoriasis. However, no significant association was observed between UPF intake and non-active psoriasis in both univariate and adjusted models.
The current study has conclusively confirmed that high UPF intake is significantly associated with active psoriasis, independent of confounding factors such as BMI, age, and comorbidities. In addition, patients with active psoriasis have a higher prevalence of obesity and comorbidities such as cardiovascular disease and diabetes compared to those without psoriasis. Taken together, these findings suggest that UPF intake may trigger the pro-inflammatory mechanisms underlying active psoriasis, providing a new direction for the prevention and treatment strategies of this disease.
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