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During medical school, a patient was described who had eluded diagnosis and was presented as a true medical mystery. She had been healthy her entire life before developing diarrhea, weight loss, fatigue, and an itchy rash on her elbows and knees. She saw doctor after doctor, but none could solve her case. Finally, a dermatologist figured it out: it was dermatitis herpetiformis, the rash associated with celiac disease. At the time, this diagnosis was portrayed as rare and the treatment nearly impossible: avoiding all gluten in the diet. That case made a huge impression on us. It shined a spotlight on the importance of diet and how it was so easily overlooked by so many. While dramatic in this case, it also hinted that diet could be playing a role in other cases, perhaps in a less dramatic, but still potentially important way.
Fast forward 20 years, and now we have whole sections of supermarkets and entire restaurants that tout a bonanza of gluten-free delights. What was once obscure has become truly mainstream, and we are now living in an era of much more sophisticated discussion around the role of diet in both health and disease. And it goes far beyond just thinking about gluten. Psoriasis, perhaps more than most other dermatologic diseases, has some important dietary considerations that are worth thinking about. While diet is generally not the main cause or triggering event for psoriasis, it seems that it can certainly play an important role.
Before we get into some of the evidence, it’s important to point out two things: First, having a good dermatologist or experienced healthcare professional as a guide is critical to success with many skin conditions. One size does not fit all, and there are many considerations, not the least of which is ensuring that the original diagnosis is correct. There are many patients who are referred to me with an incorrect diagnosis and that often explains why they were not improving–they were barking up the wrong tree. Second, while making some dietary and lifestyle changes is generally not dangerous–the thousands of diet books on the bookshelves attest to this–it is not without some risk. Dietary changes, especially the more extreme ones, can have very real and very significant health effects, including things like nutritional deficiencies. It’s very important to work with someone who is experienced and knowledgeable before undertaking significant dietary changes.
Patients with psoriasis have been found to have a higher prevalence of autoimmune conditions including celiac disease, the condition marked by sensitivity to eating gluten. Several studies suggest that psoriasis and celiac disease share common inflammatory pathways as well. Undoubtedly, for those with both psoriasis and celiac disease, avoiding gluten seems to help with both problems and is even specifically mentioned in the guidelines of the American Academy of Dermatology from 2021. While this can be a very difficult undertaking, many of my own patients have found that going gluten-free has helped their skin and their overall wellbeing. Many of them also have lost weight while being gluten free, and that leads to our next point…
Being overweight, although less specifically related to diet perhaps, is very much associated with worsening psoriasis. Generally speaking, obesity drives a number of systemic inflammatory markers like VEGF, CRP, and leptin, which seem to contribute to psoriasis. Importantly, weight loss has been convincingly shown to help improve psoriasis in a wonderful meta-analysis from 2015. And, while it is important to lose weight safely, for those of us who are overweight, there is no doubt that this can be a general key to overall health in addition to the psoriasis.
A number of studies have looked at removing foods from the diet, and while these tend to be reported by the patients themselves and not studied more rigorously, many patients (more than half, in fact) report that avoiding alcohol improved or even fully cleared their psoriasis! Other foods that are reported to lead to improvement when removed include nightshades (such as tomatoes, potatoes, eggplant, and bell peppers), products containing white flour, “junk foods” in general, dairy, and shellfish.
On the other side, patients reported that adding certain foods to the diet helped the psoriasis or even cleared their skin. These include fish oil, more vegetables, oral vitamin D supplementation, probiotics, organic foods, and fruits. (Affi et al, 2017)
In summary, diet will probably not ‘make or break’ psoriasis for most patients, but it sure seems like it can play a role for many. Losing weight if overweight, cutting out alcohol and junk foods, and eating more fruits and vegetables all seem like very reasonable advice that are difficult to argue against and really do seem to have solid evidence in their favor. Adding vitamin D supplementation, fish oil, and probiotics may also have a role in improving psoriasis, and these tend to be inexpensive and readily available.
In time we will hopefully continue to unravel the mysteries of psoriasis, but a focus on healthy eating, healthy weight, and balanced nutrition seem like invariably good advice for pretty much everyone!