High Trans‐Fat but not Saturated Fat Beverage Causes an Acute Reduction in Vascular Endothelial Function and Insulin Sensitivity in Humans

Abstract

A diet high in trans‐fatty acids (TFA) is associated with increased cardiovascular disease risk, mediated in part from dyslipidemia, endothelial dysfunction and insulin resistance. A high‐fat meal causes a transient (3‐4 hrs postprandial) reduction in endothelial function and insulin sensitivity, but studies are often confounded by meals high in carbohydrate, saturated fatty acids (SFAs) and/or TFAs. We hypothesized that a beverage high in TFA (but low in carbohydrate, SFA) would cause a larger acute reduction in endothelial function (brachial artery flow‐mediated dilation, FMD) and insulin sensitivity compared with SFA (but low in carbohydrate, TFA). Healthy non‐obese adults (n=11; 9M/2F; age=47±3 yrs) ingested a warm beverage (520kcal, 56g total fat, 5g carbohydrate), high in either TFA (42%TFA, 23%SFA; partially hydrogenated soybean oil), SFA (88%SFA, 0.2%TFA; coconut oil) or placebo (2g total fat, 5g carbohydrate) in a randomized, cross‐over study. TFA (0.19±0.02 to 0.06±0.03mm, P<0.01), but not SFA (0.14±0.03 vs. 0.11±0.04mm, P=0.49) or placebo (0.08±0.04 to 0.062±0.03mm, P=0.52), caused a reduction in FMD at 3‐4 hours (P<0.01 for time; p=0.02 for interaction effects). Postprandial glucose was reduced across groups (P<0.001), whereas the homeostasis model of insulin resistance (HOMA‐IR) decreased in SFA and placebo (P<0.001) but not TFA (1.4±0.2 vs 1.2±0.2, P=0.08, interaction P=0.02). These data suggest that ingestion of a beverage high in TFA, but not SFA, results in an acute reduction in endothelial function and insulin sensitivity in healthy adults. Supported by NIH 5T32HL007638‐28, 5T32HL007121‐3, U54TR001013.