Arterial Stiffness Interferes with LDL‐cholesterol Lowering by Canola Oil in Persons with Mild Hypercholesterolemia

Background Consumption of canola oil has been shown to lower blood cholesterol in individuals with hypercholesterolemia, which has led to investigations examining the effect of canola oil on cholesterol metabolism. However, little is known about how vascular function influences the response to canola oil on LDL‐cholesterol lowering and other risk factors associated with the metabolic syndrome (MetS). Objective To investigate the interactions among LDL‐cholesterol, vascular function and parameters of MetS (adiposity, blood glucose, triglycerides, HDL‐cholesterol, blood pressure) in individuals consuming canola oil versus a fat mixture representative of Western‐type diets. Methods Participants (n=80, 55±12 years old) invited to join the randomized controlled trial had at least two characteristics of MetS, were not taking medications for blood lipids or glucose or body weight management, and refrained from consuming omega‐3 fatty acid (FA) rich foods and supplements. They were randomized to study foods providing 25 g/d of either traditional canola oil (low SFA, high MUFA and omega‐3 FA) or a fat mixture (high SFA and omega‐6 FA, low MUFA and omega‐3 FA) to incorporate into their usual diet for 12 weeks. Assessments were conducted at baseline, 6 and 12 weeks for adiposity (dual x‐ray absorptiometry), fasting serum biochemistry, blood pressure, and non‐invasive assessments of vascular function (arterial stiffness by augmentation index at heart rate of 75 beats per minute [APGH@75] and by the small artery elasticity index [SAEI]) and advanced glycation end‐products [AGEs] (by skin autofluorescence). Results The Canola Oil Group had a significantly lower (P=0.0257) fasting total cholesterol at weeks 6 and 12 and a trend (P=0.0755) for a reduction in fasting LDL‐cholesterol at week 12. Although blood pressure and blood vessel function were not altered over the 12 week study, individuals with healthier blood vessel function (as indicated by APGH@75 ≤27% or SAEI >4.5%) had a 11–13% reduction in LDL‐cholesterol following canola oil consumption compared to 0–4% LDL‐cholesterol lowering in individuals with stiffer arteries (as indicated by APGH@75 >27% or SAEI ≤4.5%). Body fat and body composition were not altered except there was a trend (P=0.09) for those in the Canola Oil Group with a smaller waist circumference (≤101 cm) to have less android fat at 12 weeks versus baseline. Fasting blood glucose was not changed at 12 weeks, however, canola oil consumption reduced AGEs in individuals with a smaller waist circumference as compared to those consuming the fat mixture representative of a Western‐type diet. Conclusions This study has verified that dietary canola oil can lower blood cholesterol in individuals with MetS characteristics. At the same time, we observed that arterial stiffness was sufficient to make individuals resistant to cholesterol lowering by dietary canola oil. These are the first data to implicate blood vessel elasticity as a factor that influences LDL‐cholesterol lowering, and further studies are warranted to examine the mechanistic relationships underlying these unique observations. Support or Funding Information Alberta Canola Producers, Alberta Innovates Bio Solutions, and Alberta Crop Industry Development Fund

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