N-3 polyunsaturated fatty acids, inflammation and immunity:: pouring oil on troubled waters or another fishy tale?

Studies which have investigated the influence of increased consumption of n-3 polyunsaturated fatty acids (PUFA) upon indices of immune function in healthy humans are reviewed. Four studies have investigated the effects of alpha -linolenic acid (ALNA; 2 to 18 g per day). Over 25 studies have investigated the effects of the long chain n-3 PUFA and these have used 0.55 to 14.4 g eicosapentaenoic acid (EPA) plus docosahexanoic acid (DHA) per day. Studies have been of 3 to 52 weeks duration. Most studies have examined the functions of immune cells ex vivo; there are a limited number of studies reporting in vivo measures of immune status/responses. High levels of either ALNA or EPA + DHA decrease chemotaxis of neutrophils and monocytes, production of reactive oxygen species by neutrophils and monocytes, production of pro-inflammatory cytokines by monocytes and T lymphocytes, and T lymphocyte proliferation. For most of these functions it is not possible to determine dose-response relationships because of experimental differences among studies. Thus, it is not clear what the level of n-3 PUFA required to exert the different effects is. The immunological effects of large amounts of n-3 PUFA suggest that they might be useful as therapies for diseases characterized by immune dysfunction. Evidence for beneficial effects of long chain n-3 PUFA in rheumatoid arthritis is strong and there is less strong evidence for benefit in Crohn's disease, ulcerative colitis and psoriasis and among some adult asthmatics. (C) 2001 Elsevier Science Inc. All rights reserved.