EFFECT OF DIETARY SUPPLEMENTATION WITH VERY-LONG-CHAIN N-3 FATTY-ACIDS IN PATIENTS WITH PSORIASIS

Background. In several studies dietary fish oil has been found to have a beneficial effect on psoriasis, but the results are contradictory a nd based mainly on open studies or studies of small numbers of patient s. Methods. In a four-month double-blind, multicenter trial, we random ly assigned 145 patients with moderate-to-severe psoriasis to receive in their diet either highly purified ethyl esters of n-3 fatty acids ( ''fish oil''; 6 g of oil per day, containing 5 g of eicosapentaenoic a nd docosahexaenoic acid) or an isoenergetic amount of corn oil contain ing mainly n-6 fatty acids. All the patients were advised to reduce th eir intake of saturated fatty acids. A 48-hour dietary recall was perf ormed, and the fatty-acid pattern in the serum phospholipids was monit ored in a subgroup of patients. Results. In the fish-oil group, n-3 fa tty acids were increased in serum phospholipids (P<0.001), the ratio o f arachidonic acid to eicosapentaenoic acid decreased (P<0.001), and t he level of n-6 fatty acids decreased (P<0.001). In the corn-oil group , only docosahexaenoic acid increased significantly (P<0.05). The rati o of polyunsaturated to saturated fatty acids increased in both groups . Plasma concentrations of triacylglycerol decreased from base line in the fish-oil group (P<0.05). The score on the Psoriasis Area and Seve rity Index, as evaluated by the physicians, did not change significant ly during the trial in either group. This was also true of a total sub jective score reported by the patients, but a selected area of skin in the corn-oil group showed a significant reduction in the clinical sig ns (P<0.05). Scaling was reduced from base line in both groups (P<0.01 ). The fish-oil group had less cellular infiltration (P<0.01), and the corn-oil group had improvement in desquamation and redness (P<0.05). There was no clinically important difference between the two study gro ups. Among the patients in the fish-oil group, an increase in the conc entration of n-3 fatty acids in serum phospholipids was not accompanie d by clinical improvement, whereas in the corn-oil group there was a s ignificant correlation between clinical improvement and an increase in eicosapentaenoic acid and total n-3 fatty acids. Conclusions. Dietary supplementation with very-long-chain n-3 fatty acids was no better th an corn-oil supplementation in treating psoriasis. Clinical improvemen t was not correlated with an increase in the concentration of n-3 fatt y acids in serum phospholipids among the patients in the fish-oil grou p, whereas there was a significant correlation between clinical improv ement and an increase in eicosapentaenoic acid and total n-3 fatty aci ds in the corn-oil group.