Limited effect of eicosapentaenoic acid on T-lymphocyte and natural killer cell numbers and functions in healthy young males

Objective Greatly increasing the amount of long-chain ω-3 polyunsaturated fatty acids in the diet has been reported in some studies to decrease T-lymphocyte and natural killer functions. However, dose-response relations have not been identified. The objective of this study was to determine the effect of supplementing the diet of young male subjects with different amounts of an oil rich in eicosapentaenoic acid (EPA) on T-lymphocyte proliferation, cytokine production by T lymphocytes, and natural killer cell activity. Methods In a placebo-controlled, double-blind, parallel study, healthy young (18 to 42 y) males were randomized to one of four supplements. These were placebo (no additional ω-3 polyunsaturated fatty acids) or different amounts of an EPA-rich oil that provided 1.35, 2.7, or 4.05 g/d of EPA for 12 wk. Blood samples were taken at baseline and after 12 wk. Results Eicosapentaenoic acid was incorporated in a linear dose-response fashion into mononuclear cell phospholipids. EPA did not alter the proportions of T lymphocytes, helper T lymphocytes, cytotoxic T lymphocytes, B lymphocytes, or natural killer cells in the bloodstream. T-lymphocyte proliferation in response to concanavalin A and the production of the cytokines interleukin-2, interferon-γ, and interleukin-10 were not affected by the different treatments. However, interleukin-4 production was increased with increasing intake of EPA. Natural killer cell activity was little affected by the treatments, although there was a trend for EPA to increase activity at a low effector-to-target cell ratio. Conclusion T-lymphocyte and natural killer cell numbers and function in healthy young males are little affected by supplemental EPA intakes up to 4 g/d.