N-3 polyunsaturated fatty acids, inflammation and immunity: pouring oil ontroubled 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 he althy humans are reviewed. Four studies have investigated the effects of al pha -linolenic acid (ALNA; 2 to 18 g per day). Over 25 studies have investi gated 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. St udies have been of 3 to 52 weeks duration. Most studies have examined the f unctions of immune cells ex vivo; there are a limited number of studies rep orting in vivo measures of immune status/responses. High levels of either A LNA or EPA + DHA decrease chemotaxis of neutrophils and monocytes, producti on of reactive oxygen species by neutrophils and monocytes, production of p ro-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 studi es. 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 PUF A suggest that they might be useful as therapies for diseases characterized by immune dysfunction. Evidence for beneficial effects of long chain n-3 P UFA in rheumatoid arthritis is strong and there is less strong evidence for benefit in Crohn's disease, ulcerative colitis and psoriasis and among som e adult asthmatics. (C) 2001 Elsevier Science Inc. All rights reserved.