The Role of Fish Oil in Psoriasis

In a randomized, double-blind, placebo-controlled study, patients received 10 fish or olive oil capsules three times daily for the whole study in addition to applying betamethasone diproprionate to their psoriatic plaques for the first 3 weeks. Most patients gradually worsened upon discontinuation of corticosteroids. Using survival analysis methods, no significant difference was found between the fish and olive oil groups. The authors attempt to put the role of fish oil in the therapy of psoriasis Into perspective and discuss the efficacy of fish oil when used alone versus in combination therapy. There has been recent interest in the role of dietary fish oils (omega-3 polyunsaturated fatty acids) in the protection against certain conditions. These include cardiovascular disease,^ inflammatory conditions^ (eg, rheumatoid arthritis), and cutaneous diseases^"'" (psoriasis and atopic dermatitis) (Table 1). Polyunsaturated fatty acids (PUFAs) can be divided into three main groups: omega-3 fatty acids derived maitily from marine oils, omega-6 fatty acids found principally in vegetable oils (Fig. 1), and omega-9 fatty acids obtained mainly frotn animals. In the epidermis of psoriatic plaques, levels of arachidonic acid (AA) and its metabolites are markedly elevated compared to clinically uninvolved skin," In particular, tnetabolites of the 5and 12-lipoxygenase pathways such as leukotriene B4 (LTB4) and 12 hydroxyeicosatetraenoic (12 HETE) acid, both of which are chemotactic for neutrophils, are thought to Supported in part by the Babcock Endowment Fund, Address correspondence to: Aditya K, Cupta, M,D,, F,R,C,P,(C), Department of Dermatology, University of Michigan Medical Center, Room 1910TC, 1500 E, Medical Center Drive, Ann Arbor, Ml 48109-0314, Frotv the Depattment of Dermatology, University of Michigan Medical Center, Ann Arbor, Michigan play a role in psoriasis. When exogenous supplements of omega-3 PUFAs are consumed for the treatment of psoriasis, they are incorporated into cell tnembranes and compete with omega-6 PUFAs as substrates for the same 5-, 12-, and 15-lipoxygenase and cyclooxygenase pathways (Fig, 1), This results in the increased production of less biologically active leukotrienes (LTs) of the 5-series, prostaglandins (PCs) of the 3series, and 12 HEPE, with a decreased production of the LTs of the 4-series, PCs of the 2-series, and 12 HETE,'' Ptostaglandins are involved in the feedback regulation of interleukin-1 (IL-1),'^ IL-1 may be involved in keratinocyte proliferation'"* and is markedly dysregulated in psoriasis,'^ Because the antiinflammatory effects of omega-3 PUFAs may be due to decreased mononuclear cell IL-1 production,"" omega-3 PUFAs might affect the dysregulated IL-1 production by psoriatic keratinocytes. In the past we have been able to achieve only modest improvement in psoriasis using a relative high dose of eicosapentaenoic acid (EPA, 10,8-13.5 g/day) as a monotherapy with strict dietary control. Fish oil appears to be mote effective as a combination therapy with ultraviolet B̂ -" (Table 1). We decided to investigate whether fish oil would be more beneficial in combination with other standard therapies for psoriasis, compared to monotherapy, A double-blind, randomized, placebo-controlled study was therefore performed in which we used fish oil at a lower dose than our earlier study (EPA, 5,4 g/day) with a moderate potency corticosteroid (betamethasone dipro-