1. The effects of essential fatty acids (γ-linolenic acid, eicosapentaenoic acid, docosahexaenoic acid), at a dose of 4.8 g/day, given in combination as dietary supplements, on cytokine production were investigated in patients with colorectal cancer.
2. Total serum cytokines - interleukin (interleukin-1β, 2, 4 and 6), tumour necrosis factor-α and interferon-γ - were analysed using the enzyme-linked immunosorbent assay technique at different time intervals during the course of essential fatty acid supplementation.
3. Fatty acid uptake and patient compliance were confirmed by a significant increase in serum levels of γ-linolenic acid, eicosapentaenoic acid and docosahexaenoic acid in all three fractions: triacylglycerol, cholesterol and phospholipid.
4. There was no significant alteration in total serum cytokine concentration/levels in the first 2 months of essential fatty acid ingestion, but the levels of serum cytokines steadily declined thereafter, reaching minimum levels after 6 months of essential fatty acid supplementation.
5. Essential fatty acids, at the dose and duration (6 months) used in this study, reduced total serum interleukin-1β levels by 61% (P = 0.044), interleukin-2 by 63% (P = 0.05), interleukin-4 by 69% (P = 0.025), interleukin-6 by 83% (P = 0.030), tumour necrosis factor-α by 73% (P = 0.040) and interferon-γ by 67% (P = 0.050).
6. Three months after cessation of essential fatty acid intake, however, these cytokine levels returned to presupplementation values.
7. This present study has shown that long-term n-3 and n-6 EFA ingestion results in a significant reduction in circulating key cytokines. The precise mechanism of this reduction is unclear.