Lipid emulsions in parenteral nutrition: does one size fits all?

Dietary lipids significantly contribute to preserve the efficiency of human metabolism and restore it during disease. Therefore, in the absence of absolute contraindications, it would not appear reasonable to exclude lipid emulsions when prescribing parenteral nutrition (PN). The metabolic role of lipids has been elucidated, and is far more complex than a mere energy-dense source. Indeed, it is now clear that fatty acids impact differently on the inflammatory and immune responses, either promoting or blunting them. Omega-6 fatty acids are the substrate for the production of potent mediators of inflammation, whereas omega-3 fatty acids promote the synthesis of less active factors. Omega-9 fatty acids exert a more neutral impact on immune and inflammatory responses. These specific metabolic activities should therefore be considered when prescribing lipid emulsions in PN. Ideally, the metabolic profile of patients should guide the prescription of lipid emulsions in order to promote the inflammatory response or blunt it according to the clinical needs. This new approach would wholly exploit the metabolic activities of lipid emulsions by providing patients not only with an energy-dense source, but also by priming and/or modulating the immune and inflammatory responses in order to favour healing.Keywords: lipid emulsions; metabolism; parenteral nutrition; immune response; inflammatio