Psoriasis
Psoriasis is an autoimmune skin condition that has an annual prevalence ranging from approximately 1% to 9% in adults residing in Western countries.28,29 Some have argued that due to decreased bacterial diversity and increased bacterial growth in the small bowel, psoriatic patients are exposed to higher levels of bacterial peptidoglycans and endotoxins.30 To combat the absorption of these substances in psoriasis patients, we advocate for a vegetarian diet with low fats, limited alcohol consumption, and supplements of bile acids and bioflavonoid.
The effects of very long chain fatty acids also have been examined. A 4-month, double-blind, multicenter RCT compared the effects of daily supplementation with 6 g of either omega-3 fatty acids or omega-6 fatty acids in patients with mild to moderate plaque psoriasis.31 Psoriasis area and severity index scores and patient subjective scores did not change significantly in either group; however, scaling was reduced in both groups (P<.01). The group receiving omega-3 fatty acids had decreased cellular infiltration (P<.01), and the group receiving omega-6 fatty acids had decreased desquamation and redness (P<.05). In the omega-6 group, there was a significant correlation between clinical improvement (decrease in clinical score) and increase in serum eicosapentaenoic acid (r=−0.34; P<.05) and total omega-3 fatty acids (r=−0.36; P<.05). Overall, the authors concluded that supplementation with omega-3 fatty acids (fish oil) was no better than omega-6 fatty acids (corn oil) for treatment of psoriasis.31
Some dermatologists have advocated for the use of oral vitamin D supplementation as an adjunctive treatment of psoriasis, given that it is inexpensive and also may play a role in reducing the risk for cancer and cardiovascular events.32 One study evaluated the level of 25-hydroxy vitamin D in 43 psoriasis patients compared to 43 healthy controls. Mean (SD) vitamin D levels were significantly lower in psoriasis patients (13.3 [6.9]) compared to controls (22.4 [18.4])(P=.004).33 A cross-sectional study similarly found significantly higher rates of vitamin D deficiency (25-hydroxy vitamin D <20 ng/mL) in psoriatic patients (57.8%) compared to patients with rheumatoid arthritis (37.5%) and healthy controls (29.7%)(P<.001). Interestingly, during winter the prevalence of vitamin D deficiency increased to 80.9%, 41.3%, and 30.3% in the 3 groups, respectively; however, no significant correlation was seen between psoriasis severity, as measured by psoriasis area and severity index, and serum vitamin D levels.34 Although vitamin D deficiency may be more prevalent among patients with psoriasis, data regarding the efficacy of treating psoriasis with oral vitamin D supplementation is still lacking.
Conclusion
Our understanding of the link between diet and dermatologic conditions continues to evolve. Recent data for several dietary supplements and therapies showed promising results in repairing signs of photoaging, as well as treating AV, AD, and psoriasis. As patients seek these adjunctive therapies, it is important for physicians to be well informed on the benefits and risks to appropriately counsel patients.
Globally, physicians advocate for a low-glycemic diet rich in fruits and vegetables. Furthermore, the cosmetic diet can be enhanced by the consumption of dietary supplements such as beta-carotene, collagen peptides, zinc, and fat-soluble vitamins such as vitamins D and E. However, prospective RCTs are needed to further investigate the role of these dietary elements in treating and improving dermatologic conditions.