N-3 fatty acids and diabetes.

Fatty acids of the omega-3 series (n-3 fatty acids) are a well established dietary component affecting plasma lipids (mainly triglycerides) and also major cardiovascular parameters, such as arrhythmogenesis. In view of their peculiar metabolic handling, it has been suggested that they may reduce glucose tolerance in patients predisposed to diabetes. On the other hand, insulin is required for the endogenous synthesis of the long chain n-3 fatty acids from precursors; the heart may thus be particularly susceptible to their depletion in diabetes. This review examines large population studies, carried out particularly by this research group, evaluating the risk of developing glucose intolerance/clearcut diabetes in large series of patients with predisposing conditions. While diabetes development was in no way accelerated in any of these studies, there was, instead, clear evidence of a significant hypotriglyceridemic activity of the supplements. In long-term treatments, there was also a tendency toward a significant reduction of low density lipoprotein (LDL) cholesterolemia, with positive effects on high density lipoprotein (HDL). These findings fit well with cellular changes indicative of improved glucose handling. Finally, recent data suggest an improvement of heart rate variability by fish intake in coronary patients, that is also exerted by the n-3 fatty acids given as ethyl esters, thus providing further indication for the potential benefit of such treatments in diabetic patients.