Inflammation is part of the normal host response to infection and injury. However, excessive or inappropriate inflammation contributes to a range of acute and chronic human diseases and is characterized by the production of inflammatory cytokines, arachidonic acid-derived eicosanoids (prostaglandins, thromboxanes, leukotrienes, and other oxidized derivatives), other inflammatory agents (eg, reactive oxygen species), and adhesion molecules. At sufficiently high intakes, long-chain nҀ3 polyunsaturated fatty acids (PUFAs), as found in oily fish and fish oils, decrease the production of inflammatory eicosanoids, cytokines, and reactive oxygen species and the expression of adhesion molecules. Long-chain nҀ3 PUFAs act both directly (eg, by replacing arachidonic acid as an eicosanoid substrate and inhibiting arachidonic acid metabolism) and indirectly (eg, by altering the expression of inflammatory genes through effects on transcription factor activation). Long-chain nҀ3 PUFAs also give rise to a family of antiinflammatory mediators termed resolvins. Thus, nҀ3 PUFAs are potentially potent antiinflammatory agents. As such, they may be of therapeutic use in a variety of acute and chronic inflammatory settings. Evidence of their clinical efficacy is reasonably strong in some settings (eg, in rheumatoid arthritis) but is weak in others (eg, in inflammatory bowel diseases and asthma). More, better designed, and larger trials are required to assess the therapeutic potential of long-chain nҀ3 PUFAs in inflammatory diseases. The precursor nҀ3 PUFA ␣-linolenic acid does not appear to exert antiinflammatory effects at achievable intakes.Am J Clin Nutr 2006;83(suppl):1505S-19S.

Total parenteral nutrition is the final option for nutritional support of patients with severe intestinal failure. Lipid emulsions constitute the main source of fuel calories and fatty acids (FAs) in parenteral nutrition formulations. However, adverse effects on patient outcomes have been attributed to the use of lipids, mostly in relation to impaired immune defenses and altered inflammatory responses. Over the years, this issue has remained in the limelight, also because technical advances have provided no safeguard against the most daunting problems, ie, infectious complications. Nevertheless, numerous investigations have failed to produce a clear picture of the immunologic characteristics of the most commonly used soybean oil-derived lipid emulsions, although their high content of n-6 polyunsaturated FAs (PUFAs) has been considered a drawback because of their proinflammatory potential. This concern initiated the development of emulsions in which part of the n-6 FA component is replaced by less bioactive FAs, such as coconut oil (rich in medium-chain saturated FAs) or olive oil (rich in the n-9 monounsaturated FA oleic acid). Another approach has been to use fish oil (rich in n-3 PUFA), the FAs of which have biological activities different from those of n-6 PUFAs. Recent studies on the modulation of host defenses and inflammation by fish-oil emulsions have yielded consistent data, which indicate that these emulsions may provide a tool to beneficially alter the course of immune-mediated conditions. Although most of these lipids have not yet become available on the US market, this review synthesizes available information on immunologic characteristics of the different lipids that currently can be applied via parenteral nutrition support.

Older subjects incorporate EPA into plasma and MNC phospholipids more readily than do younger subjects. Other than prostaglandin E2 production, innate immune responses in young subjects are not affected by an EPA intake of < or =4.05 g/d. Older subjects are more sensitive to the immunologic effects of EPA, and the neutrophil respiratory burst is lower at higher EPA intakes.

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Supplementation of the diet with 3.2 g EPA plus DHA per day markedly alters plasma phospholipid and PBMC fatty acid compositions. The lack of effect of FO upon PBMC functions may relate to the level of alpha-tocopherol included in the supplements.

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There has been a great deal of research in recent years regarding the biological processes by which fatty acids influence inflammation. The findings indicate one connection between the human diet and many common chronic conditions, including arthritis, inflammatory bowel diseases, asthma, multiple sclerosis, and neurodegeneration. Studies indicate that increased intake of certain fatty acids, such as those found in fish oils, may help to reduce inflammation and thereby reduce symptoms associated with these chronic diseases.In this chapter, the variety of fatty acids in the human diet is described, along with naming conventions and the metabolic relationships between the different types. Next, the effects of omega-3 (n-3) polyunsaturated fatty acids (PUFAs) on several components of the inflammatory process are described. These components include leukocyte chemotaxis (i.e, the process of movement of cells toward a site of inflammatoty activity in response to chemicals released at that site). The second component is expression of adhesion molecules that allow leukocytes to interact with the endothelium and so to move from the bloodstream into tissue sites of inflammatory activity.

Divergent effects of cis-9,trans-11 CLA and trans-10,cis-12 CLA appear on the blood lipid profile in healthy humans: trans-10,cis-12 CLA increases LDL:HDL cholesterol and total:HDL cholesterol, whereas cis-9,trans-11 CLA decreases them.