Effects of stereospecific positioning of fatty acids in triacylglycerol structures in native and randomized fats: a review of their nutritional implications

Abstract

Most studies on lipid lowering diets have focused on the total content of saturated, polyunsaturated and monounsaturated fatty acids. However, the distribution of these fatty acids on the triacylglycerol (TAG) molecule and the molecular TAG species generated by this stereospecificity are characteristic for various native dietary TAGs. Fat randomization or interesterification is a process involving the positional redistribution of fatty acids, which leads to the generation of new TAG molecular species. A comparison between native and randomized TAGs is the subject of this review with regards to the role of stereospecificity of fatty acids in metabolic processing and effects on fasting lipids and postprandial lipemia. The positioning of unsaturated versus saturated fatty acids in the sn-2 position of TAGs indicate differences in early metabolic processing and postprandial clearance, which may explain modulatory effects on atherogenecity and thrombogenecity. Both human and animal studies are discussed with implications for human health.

Figure 1

Triacylglycerol molecule structure before and after interesterification. An example of a triacylglycerol molecule (POL) that occurs in oils and fats is depicted in which palmitic (P), oleic (O) and linoleic (L) fatty acids occupy the Sn1, 2 and 3 positions respectively. Following interesterification (IE) by either chemical or enzymatic methods, these fatty acids are rearranged and take new forms, which would include LPO (linoleic-palmitic-oleic), OLP (oleic-linoleic-palmitic) and PLO (palmitic-linoleic-oleic) among the various permutations that are possible. Since natural oils and fats are made up of a variety of triacylglycerol molecules, interesterification will result in a large number of new triacylglycerol molecules.