DHA-enriched high-oleic acid canola oil improves lipid profile and lowers predicted cardiovascular disease risk in the canola oil multicenter randomized controlled trial

Abstract

Background: It is well recognized that amounts of trans and saturated fats should be minimized in Western diets; however, considerable debate remains regarding optimal amounts of dietary n-9, n-6, and n-3 fatty acids.

Objective: The objective was to examine the effects of varying n-9, n-6, and longer-chain n-3 fatty acid composition on markers of coronary heart disease (CHD) risk.

Design: A randomized, double-blind, 5-period, crossover design was used. Each 4-wk treatment period was separated by 4-wk washout intervals. Volunteers with abdominal obesity consumed each of 5 identical weight-maintaining, fixed-composition diets with one of the following treatment oils (60 g/3000 kcal) in beverages: 1) conventional canola oil (Canola; n-9 rich), 2) high-oleic acid canola oil with docosahexaenoic acid (CanolaDHA; n-9 and n-3 rich), 3) a blend of corn and safflower oil (25:75) (CornSaff; n-6 rich), 4) a blend of flax and safflower oils (60:40) (FlaxSaff; n-6 and short-chain n-3 rich), or 5) high-oleic acid canola oil (CanolaOleic; highest in n-9).

Results: One hundred thirty individuals completed the trial. At endpoint, total cholesterol (TC) was lowest after the FlaxSaff phase (P < 0.05 compared with Canola and CanolaDHA) and highest after the CanolaDHA phase (P < 0.05 compared with CornSaff, FlaxSaff, and CanolaOleic). Low-density lipoprotein (LDL) cholesterol and high-density lipoprotein (HDL) cholesterol were highest, and triglycerides were lowest, after CanolaDHA (P < 0.05 compared with the other diets). All diets decreased TC and LDL cholesterol from baseline to treatment endpoint (P < 0.05). CanolaDHA was the only diet that increased HDL cholesterol from baseline (3.5 ± 1.8%; P < 0.05) and produced the greatest reduction in triglycerides (-20.7 ± 3.8%; P < 0.001) and in systolic blood pressure (-3.3 ± 0.8%; P < 0.001) compared with the other diets (P < 0.05). Percentage reductions in Framingham 10-y CHD risk scores (FRS) from baseline were greatest after CanolaDHA (-19.0 ± 3.1%; P < 0.001) than after other treatments (P < 0.05).

Conclusion: Consumption of CanolaDHA, a novel DHA-rich canola oil, improves HDL cholesterol, triglycerides, and blood pressure, thereby reducing FRS compared with other oils varying in unsaturated fatty acid composition. This trial was registered at www.clinicaltrials.gov as NCT01351012.

FIGURE 1.

Flow of participants throughout the study.

FIGURE 2.

Percentage change in serum lipids from treatment-specific baseline in response to 5 treatment diets. Percentage change was calculated from the baseline value of each dietary phase. The bars represent least-squares means for n = 130. The error bars reflect SEMs. The treatment effect was analyzed by using a mixed model with repeated measures adjusted by Tukey's test for multiple comparisions. Mean values with different lowercase letters are significantly different, P < 0.05. Canola, conventional canola oil (Richardson Oilseed Ltd); CanolaDHA, high–oleic acid canola oil (Richardson Oilseed Ltd) with DHA (Martek Biosciences Corporation); CanolaOleic, high–oleic acid canola oil; CornSaff, corn oil (Loblaws Inc) and safflower oil (Loblaws Inc) blend; FlaxSaff, flax oil (Shape Foods Inc) and safflower oil blend; HDL-C, HDL cholesterol; LDL-C, LDL cholesterol; TC, total cholesterol; TG, triglycerides.

FIGURE 3.

Comparison of percentage changes in Framingham 10-y coronary heart disease risk scores after 5 treatment diets. Percentage changes were calculated from baseline Framingham 10-y coronary heart disease risk scores of each dietary phase. The bars reflect the least-squares means (n = 130). The error bars reflect SEMs. The treatment effects were analyzed by using a mixed model with repeated measures adjusted by Tukey's test. Mean values with different lowercase letters are significantly different, P < 0.05. Canola, conventional canola oil (Richardson Oilseed Ltd); CanolaDHA, high–oleic acid canola oil (Richardson Oilseed Ltd) with DHA (Martek Biosciences Corporation); CanolaOleic, high–oleic acid canola oil; CornSaff, corn oil (Loblaws Inc) and safflower oil (Loblaws Inc) blend; FlaxSaff, flax oil (Shape Foods Inc) and safflower oil blend.