Medical nutrition therapy as a potential complementary treatment for psoriasis—five case reports

Alternative Medicine Review, Sept, 2004 by Amy C. Brown, Michelle Hairfield, Douglas G. Richards, David L. McMillin, Eric A. Mein, Carl D. Nelson

In addition, allergic reactions often occur due to dietary proteins. If a compromised gastrointestinal tract allows protein substances larger than amino acids to pass into the bloodstream, then the body may react in an allergic-type fashion, resulting in one of the symptoms of allergies--a skin manifestation. Since allergic reactions are inflammatory responses involving the immune system, it is interesting to note psoriasis is an inflammatory condition that appears to benefit from newer immune therapies. The fact that a gluten-free diet improves the condition of some people with psoriasis (8) indicates the gastrointestinal tract may be involved.

Another important aspect of this diet was elimination of alcohol. Consumption of alcohol is a known trigger of psoriasis flare-ups. Although the mechanism is unknown, possible reasons for an alcohol trigger include stress on the liver or alcohol-induced increase in gut permeability. The fact that dialysis is effective in the treatment of psoriasis (34-37) indicates there may be substances in the blood, removed through dialysis, that can exacerbate psoriasis, such as endotoxins, immune complexes, or other substances related to the body's immune reaction. The authors believe this elusive mechanism involving the gastrointestinal tract, liver, and bloodstream holds the key to the core cause, and therefore effective treatment, for psoriasis. If this is the case, topical treatments or systemic anti-inflammatory medications are doing little to treat the cause of psoriasis. Perhaps this is why so few psoriasis treatments are successful.

Generous consumption of fresh fruits and vegetables was also a significant feature of the diet of the test subjects. The resulting boost in consumption of fiber may have aided in diminishing psoriasis symptoms. Both bacteria and yeasts inhabit the bowels and produce byproducts that may be carried away by fiber components (52) for elimination. Further hypothesizing the autointoxication theory, some of these byproducts from the intestine, such as endotoxins, may enter the systemic circulation due to intestinal hyperpermeability, leading to higher skin cGMP levels and the resulting rapid skin cell proliferation seen in psoriatics. (52) By increasing daily fiber intake it is possible to decrease the absorption of endotoxins, which could reduce cGMP levels in skin. Some researchers suggest a high-fiber, vegetarian diet also supports a healthy balance of normal intestinal microflora. Conversely, a diet high in animal protein encourages the growth of the microorganisms that produce endotoxins. (53,54)

Another aspect of diet that has been researched among psoriasis patients is the use of omega-3 fatty acid supplementation. Overall, fish oil consumption results in mild-to-modest improvement in psoriatic symptoms, (66,55-57) although some studies show fish oil was not superior to corn oil (58) or olive oil. (59) Psoriatic plaques have been shown to increase arachidonic acid and leukotriene levels (60) compared to normal skin. Arachidonic acid is an omega-6 fatty acid contained in animal products that, when metabolized, produces potent inflammatory leukotrienes. Leukotrienes are promoters of increased cGMP levels. (16,60) On the other hand, eicosapentaenoic acid (EPA), one of the active components offish oil, serves as a substrate for the production of anti-inflammatory prostaglandins. (61) In most of the studies employing fish oil supplementation, the diets of the subjects involved were not altered (55,57,62) and results have shown only slight improvement. This may have been due to the fact that study subjects continued to eat red meat; hence, arachidonic acid was in competition with the EPA. In the present study, however, all meat from sources other than fish, fowl, and lamb were excluded. Although arachidonic acid levels were not measured in this study, decreasing the intake of red meat and therefore arachidonic acid, and substituting protein from fish, consequently increasing EPA levels, may have contributed to decreased levels of leukotrienes, cGMP, and cellular proliferation.