November 27, 2024

expert reaction to a study looking at the association between Ultraprocessed Food Intake and Psoriasis

A study published in JAMA Dermatology looks at association between ultra-processed food (UPF) intake and Psoriasis. 

Prof Wendy Hall, Department of Nutritional Sciences, King’s College London, said:

“The study is a cross-sectional study in a French cohort, where participants who have never had psoriasis are compared with those who have active psoriasis and those who have had psoriasis but it is not currently active in terms of their dietary intakes of ultra-processed foods (UPF). This type of study can only tell us if diet is associated with a health outcome, not the direction of effect (e.g. having active psoriasis may impact mental health and consequently food choices) nor if diet is actually causing a health outcome. Although this type of study is commonly conducted and is useful for indicating aspects of diet that might be linked with health it does not yield evidence that is strong enough to form the basis of dietary guidelines without additional controlled intervention trials to confirm a causal link. The authors report that participants with active psoriasis are more like to have higher intakes of UPF compared to individuals who have never has psoriasis. There is no difference in UPF intakes in the group with non-active psoriasis compared to the group who have never had psoriasis. No comparison between the non-active and active psoriasis groups has been included in the report.

“The article is a brief research letter rather than a full article, and therefore limited information is provided on methodology used to assess UPF intake. A strength of the analysis is that the analysis was adjusted for confounding factors including body mass index (BMI), which is important as a high BMI is a result of high intake of energy-dense foods and is also a risk factor for psoriasis. The topic of diet and psoriasis has been relatively understudied so it is important that associations are explored in large cohorts such as this one in order to generate hypotheses that can be tested in randomised controlled trials, and then eventually support development of clinical dietary guidelines.

“It isn’t clear how UPF were classified but the same authors have previously published a similar cross-sectional analysis in the same Nutri-Net-Santé cohort using the NOVA system¹, an imprecise and controversial attempt to classify foods according to their degree of processing. Although this report underlines recent headlines about UPF intakes being associated with a wide range of chronic disease risks, it does not add particularly new information to the poorly researched area of diet and psoriasis. The authors’ previous work has already reported that individuals from the Nutri-Net- Santé cohort with severe psoriasis have low adherence to a Mediterranean diet, a healthy dietary pattern (rich in fruits and vegetables, unsaturated fats, nuts, whole grains and oily fish) that is known to be protective against inflammatory diseases such as heart disease². The reported findings that study participants with active psoriasis are more likely to consume higher amounts of UPF compared to those who have never had psoriasis likely reflects the fact that the majority of foods classified as UPF are also high-sugar, high-fat, high-salt, energy-dense and low in micronutrients, fibre and non-nutrient bioactives, and by definition are not food groups that are encouraged in dietary guidelines e.g. fruits and vegetables, oily fish, nuts. Overall UPF is generally a rather vague proxy for a poor nutritional profile and is not well-defined in terms of other aspects such as additives or the type/level of physical processing. In summary, these findings indicate that a calorie-dense dietary pattern characterised by high-sugar/high-fat/high-salt foods is associated with increased likelihood of having active psoriasis compared to those who have never had psoriasis. There is no indication whether there is any association with likelihood of having active psoriasis compared with those who have non-active psoriasis. In terms of generating evidence to help inform the development of tangible, achievable advice for patients with psoriasis it would be more helpful to have observational analyses based on food groups and precisely defined dietary patterns that are easy to communicate to patients and achievable for most people.”

1 – Srour B, Fezeu LK, Kesse-Guyot E, et al. Ultraprocessed Food Consumption and Risk of Type 2 Diabetes Among Participants of the NutriNet-Santé Prospective Cohort. JAMA Intern Med. 2020;180(2):283–291. doi:10.1001/jamainternmed.2019.5942

2 – Phan C, Touvier M, Kesse-Guyot E, et al. Association Between Mediterranean Anti-inflammatory Dietary Profile and Severity of Psoriasis: Results From the NutriNet-Santé Cohort. JAMA Dermatol. 2018;154(9):1017–1024. doi:10.1001/jamadermatol.2018.2127

‘Ultraprocessed Food Intake and Psoriasis’ by Penso et al., 2024 was published in JAMA Dermatology at 16:00 UK time on Wednesday 27^th November 2024. 

DOI: 10.1001/jamadermatol.2024.4832

Declared interests:

Prof Wendy Hall “Trustee of the Nutrition Society. Consultant to Zoe Ltd. Research funding from Psoriasis Association, British Skin Foundation, Almond Board of California, Alliance for Potato Research & Education. Research collaboration with Yakult and funding to attend a scientific conference from Yakult. Previous research collaboration and funding from Lucozade Ribena Suntory and Diana Foods Ltd.”