Abstract/Summary

Background: Interesterified (IE) fats are widely used in place of trans fats; however, little is known about their metabolism. Objective: To test the impact of a commonly consumed IE versus a non-IE equivalent fat on in vivo postprandial and in vitro lipid metabolism, compared with a reference oil (rapeseed oil; RO). Design: A double-blinded, 3-phase crossover, randomized controlled trial was performed in healthy adults (n=20) aged 45-75 years. Postprandial plasma triacylglycerol (TG) and lipoprotein responses (including stable isotope tracing) to a test meal (50g fat) were evaluated over 8 hours. The test fats were IE 80:20 palm stearin/palm kernel fat, an identical non-IE fat, and RO (control). In vitro, mechanisms of digestion were explored using a dynamic gastric model (DGM). Results: Plasma TG 8h incremental area under the curves were lower following non-IE versus RO (-1.7 mmol/L.h (95% confidence interval -3.3, -0.0)), but there were no differences between IE and RO nor IE and non-IE. Low density lipoprotein (LDL) particles were smaller following IE and non-IE versus RO (P=0.005). Extra, extra large (XXL)-, extra large (XL)- and large (L)- VLDL particle concentrations were higher following IE and non-IE versus RO at 6-8 h (P <0.05). No differences in the appearance of [13C]palmitic acid in plasma TG was observed between IE and non-IE fats. DGM revealed differences in phase separation of the IE and non-IE meals and delayed release of saturated fatty acids (SFA) versus RO. Conclusions: Interesterification did not modify fat digestion, postprandial lipemia or lipid metabolism measured by stable isotope and DGM analysis. Despite the lower lipemia following the SFA rich fats, increased pro-atherogenic large TG-rich lipoprotein remnant and small LDL particles following the SFA rich fats relative to RO adds a new postprandial dimension to the mechanistic evidence linking SFA to cardiovascular disease risk.