"A pesar de extensas investigaciones que se han llevado a cabo a lo largo de esto últimos 30 años sobre los efectos promovidos por los lípidos en la dieta sobre el sistema inmune tanto del ser humano como de los animales, avances recientes han revelado numerosas discrepancias apoyados por los datos experimentales y clínicos. Estas investigaciones han corroborado que la acción de ciertos lípidos de la dieta sobre las funciones del sistema inmune depende de diferentes factoers, como el tipo de microorganismo, la clase del ácido graso, la concentración, la metodología del estudio, la dosis, o la vía de infección...."
Despite extensive investigations during the last 30 years into the effects promoted by dietary lipids on the immune system of both humans and animals, recent advances have revealed numerous discrepancies supported by experimental and clinical data. These investigations have corroborated that the action of certain dietary lipids on immune system functions depends on different factors, such as type of microorganism, class of fatty acid, concentration, methodology of the study, dose, or route of infection.
Therefore, in the light of current experimental observations, it is clear that certain fatty acids modulate the immune system in both animals and humans, and various immunological parameters are considerably altered. Thus, it is generally accepted that lymphocyte proliferation, cytokine synthesis, NK cell activity, or adhesion molecules are affected after the administration of diets containing n-3 polyunsaturated fatty acids or n-9 monounsaturated fatty acids. As a direct consequence of these events, certain fatty acids have been applied in the reduction of inflammatory disorders, which are characteristics of autoimmune diseases.
Nevertheless, the immunosuppression carried out by certain unsaturated fatty acids (particularly long-chain n-3 polyunsaturated fatty acids, the most immunosuppressive fatty acids) may lead to a significant increase of susceptibility to different infectious microorganisms, or in other words, to a loss of host immune resistance against viruses, bacteria, or parasites. In contrast, other studies have suggested that long-chain n-3 polyunsaturated fatty acids improve the immune resistance, and therefore significantly reduce the susceptibility of both animals and humans to infection.
Therefore, it is clear that future investigations should be focused on the relationship between certain fatty acids and the potential consequences in the clinical application of these nutrients, because several parenteral lipid emulsions (administered to patients at risk of sepsis) are currently applied in clinical nutrition as a potential alternative to others which have classically been used.
Nowadays, the administration of an olive oil–containing emulsion (ClinOleic or SMOFLipid) appears to be more beneficial to immune system functions than soybean oil–based emulsions, because it does not alter inflammatory cytokine production. Despite optimistic results, the effect of olive oil–containing emulsion needs to be corroborated by more, randomized clinical trials. Similarly, enteral immunonutrient mixtures (which include arginine, nucleotides, and long-chain n-3 polyunsaturated fatty acids) have been applied in surgical and critically ill patients. Nevertheless, the efficacy of these immunonutrient mixtures remains controversial, particularly in critically ill patients. Cautious use of these new lipid emulsions is essential to establish the impact of these lipid emulsions on the immune system.