THE NEW DIETARY FATS IN HEALTH AND DISEASE

Lipids are an integral part of the routine diet of patients and the ge neral public. Ln this article, the physiologic properties of various d ietary lipids are reviewed, beginning with those most commonly consume d - the long-chain triglycerides (LCTs) and extending to those with sp ecial purposes: the short- and medium-chain triglycerides. The nutriti onal dietary management of patients typically includes physical mixtur es of lipids. Recently, structured triglycerides (STs), which combine advantages from conventional fats with those of special purposes, have become available. STs are currently developed Gy interesterifying a m ixture of conventional fats and oils. usually with medium-chain trigly cerides, to achieve a specific fatty acid profile. This results in a t riglyceride containing combinations of short-, medium-, and long-chain fatty acids on a single glycerol backbone. They have unique chemical. physical, or physiologic properties that are not observed by simply b lending mixtures of the starting fats and oils. A number of STs are un der intense laboratory and clinical investigation in models of cancer, burns, and immune dysfunction. Much interest in the fatty acids resid es in the sn-2 position on the glycerol molecule. This is because the fatty acid in the sn-2 position of triglycerides is preferentially abs orbed as the 2-monoglyceride and selves as the template for reesterifi cation by intestinal cells to re-form triglycerides. The sn-2 fatty ac ids are also preferentially preserved as components of chylomicrons an d very-low-density lipoprotein particles for ultimate incorporation in tissue membranes. Technology is evolving to create STs with a selecte d fatty acid in this sn-2 position. For instance, incorporating linole ic, arachidonic. or eicosapentaenoic acid at the sn-2 position is bein g evaluated for the specific objective of modulating serum cholesterol concentrations and essential fatty acid absorption (a review of this work is included).