Modulation of immune and inflammatory responses by dietary lipids

PURPOSE OF REVIEW: There continues to be considerable interest in the modulating effect of dietary lipids on immune and inflammatory responses. Although controversy still exists in research in this area, new concepts and approaches have emerged providing useful suggestions. Analysis of the recent findings will help in understanding certain paradoxical findings as well as introducing new strategies to guide future studies. RECENT FINDINGS: The tissue polyunsaturated fatty acid composition was found to be correlated with changes in certain indices of immune function in individuals consuming habitual diets. It seems that individuals or animals with disordered immune systems are more reactive to polyunsaturated fatty acid supplementation, and genetic variation is also a determinant. N-3 polyunsaturated fatty acids were shown to reduce both resistance to bacterial infection and host survival. The studies on other non-classic fatty acids also demonstrated interesting findings. A proposed immuno-enhancing effect of conjugated linoleic acid has not been confirmed by studies and even an adverse effect has been implied. Trans fatty acids have been shown to increase the production of inflammatory cytokines, which may contribute to their pro-atherogenic property. SUMMARY: Current data suggest that the intake of polyunsaturated fatty acids, particularly n-3 polyunsaturated fatty acids, can modulate immune and inflammatory responses, although a discrepancy is still present. Some recent studies have provided useful information explaining possible underlying reasons. Factors such as genetic variation, health status, disease, immune response stage, stimulation type, and possibly age, all contribute to the responsiveness to polyunsaturated fatty acid supplementation in terms of immune function.