Psoriasis is a chronic inflammatory disorder affecting more than 2-8% of United Kingdom population. (Springate et al., 2017) It is characterized by erythematous, well-demarcated, scaly plaques that are prominent on visual inspection, psychologically depressing and disfiguring for the patients. This disease has been known to have close relationship with metabolic syndrome, obesity, and cardiovascular diseases to name a few. The exact mechanism is not clearly understood but we know that adipocytes do release pro-inflammatory cytokines for example IL-6, TNF-alpha and MCP-1. IL-17 and IL-23 have been found elevated in obese patients with psoriasis. Now we even have drugs targeting these particular cytokine receptors. These are the very mediators that are released in obese psoriasis patient as compared to patients that have low body fat that make the disease worsen. In this paper I will try to discuss the effect of weight loss and dietary change in psoriasis severity. (Debbaneh et al., 2014)
Body mass index and psoriasis: Several studies conducted in the past decade has compared the relation between psoriasis and body mass index. One of the case-control studies of around 373 psoriasis patients compared with healthy control found a 9% increased risk for psoriasis onset and 7% higher risk of increased PASI score for every one unit increase in body mass index. (Wolk et al., 2009). The Nurses’ Health Study prospectively studied around 67,300 female nurses and found a 1.63 times increased risk for psoriasis incidence in nurses with BMI more than 35. (Kumar et al., 2012). A large population study of 75,395 patients found that obesity was a risk factor for developing psoriatic arthritis. The pathophysiology of TNF-alpha in psoriatic arthritis and release of the very cytokine by adipocytes make it have a strong correlation. (Jon Love et al., 2012)
Diet changes on the severity of psoriasis:
- Low-calorie diet (LCD): Di Minno et. al have shown that low-calorie diet is able to reduce the severity of psoriasis if weight loss is more than 5% of baseline. (Di Minno et al., 2014) In another study, calorie restriction with topical steroids was given to 40 patients for four weeks and compared to control. The patients in treatment group had a more significant decrease in psoriasis severity, serum triglyceride, cholesterol, and LDL as compared to the control group. (Rucević et al., 2003)
- Gluten-free diet (GFD): Patients with psoriasis and anti-gliadin antibodies have shown some improvements in their psoriasis severity (Chalmers and Kirby, 2000) however patients without having anti-gliadin antibodies if put on gluten free diet showed no or minimal improvement in their psoriasis. (Zamani et al., 2010)
- Mediterranean diet: Barrea L. et al did a cross-sectional case-control observational study in 2015 that patients on a Mediterranean diet showed a lower PREDIMED score and improved PASI scores. The concluded that Mediterranean food pattern rich in extra virgin olive oil, fruits, vegetables, fish, chicken and whole grains could be a cheap alternative in addition to medications for improvement in psoriatic patients. (Barrea et al., 2015).
- Fish oil: Most of the trials from 1980s to 1990s showed that addition of fish oil in the diet of psoriasis patients improved their PASI scores and increased their favorable neutrophilic cytokines. The docosahexanoic acid dose with most effect was found out to be 1.2 g or more. (Bittiner et al., 1988; Grimminger et al., 1993; Mayser et al., 1998)
- Vitamin D: Vitamin D deficiency has been reported to be linked with psoriasis and psoriatic arthritis. (El-Moaty Zaher et al., 2013) There have been few studies done on the linkage between supplementation of Vitamin D in psoriasis and its effects. The trials varied from using 1,25-dihydroxyvitamin D3 to 1-alpha-hydroxyvitamin D3. The results varied from 12% patients (el-Azhary et al., 1993) showing improvement all the way to 76% showing improvement. (Morimoto et al., 1986)
- Gastric bypass surgery: Hossler et. al conducted a retrospective study on 34 patients and found that 62% of respondents reported improvement in their psoriasis after surgery. (Hossler et al., 2013). A case series done by Farias et. al on patients with a BMI of 38.3 kg/m2 undergoing bariatric surgery seventy percent reported complete resolution of their psoriasis lesions. (Farias et al., 2012) Al though bariatric surgery is not the first line treatment in psoriatic patients but patients undergoing this procedure for other indications and had psoriasis showed these observations.