Effects of Diets Enriched with Conventional or High-Oleic Canola Oils on Vascular Endothelial Function: A Sub-Study of the Canola Oil Multi-Centre Intervention Trial 2 (COMIT-2), a Randomized Crossover Controlled Feeding Study.

Partial replacement of saturated fatty acids (SFA) with unsaturated fatty acids is recommended to reduce cardiovascular disease (CVD) risk. Monounsaturated fatty acids (MUFA), including oleic acid, are associated with lower CVD risk. Measurement of flow-mediated dilation of the brachial artery (FMD) is the gold standard for measuring endothelial function and predicts CVD risk. This study examined the effect of partially replacing SFA with MUFA from conventional canola oil and high-oleic acid canola oil on FMD. Participants (n = 31) with an elevated waist circumference plus ≥1 additional metabolic syndrome criterion completed FMD measures as part of the Canola Oil Multi-Centre Intervention Trial 2 (COMIT-2), a multi-center, double-blind, three-period crossover, controlled feeding randomized trial. Diet periods were 6 weeks, separated by ≥4-week washouts. Experimental diets were provided during all feeding periods. Diets only differed by the fatty acid profile of the oils: canola oil (CO; 17.5% energy from MUFA, 9.2% polyunsaturated fatty acids (PUFA), 6.6% SFA), high-oleic acid canola oil (HOCO; 19.1% MUFA, 7.0% PUFA, 6.4% SFA), and a control oil blend (CON; 11% MUFA, 10% PUFA, 12% SFA). Multilevel models were used to examine the effect of the diets on FMD. No significant between-diet differences were observed for average brachial artery diameter (CO: 6.70 ± 0.15 mm, HOCO: 6.57 ± 0.15 mm, CON: 6.73 ± 0.14 mm; p = 0.72), peak brachial artery diameter (CO: 7.11 ± 0.15 mm, HOCO: 7.02 ± 0.15 mm, CON: 6.41 ± 0.48 mm; p = 0.80), or FMD (CO: 6.32 ± 0.51%, HOCO: 6.96 ± 0.49%, CON: 6.41 ± 0.48%; p = 0.81). Partial replacement of SFA with MUFA from CO and HOCO had no effect on FMD in participants with or at risk of metabolic syndrome.

Polymorphisms in the stearoyl-CoA desaturase gene modify blood glucose response to dietary oils varying in MUFA content in adults with obesity.

Diets varying in SFA and MUFA content can impact glycaemic control; however, whether underlying differences in genetic make-up can influence blood glucose responses to these dietary fatty acids is unknown. We examined the impact of dietary oils varying in SFA/MUFA content on changes in blood glucose levels (primary outcome) and whether these changes were modified by variants in the stearoyl-CoA desaturase (SCD) gene (secondary outcome). Obese men and women participating in the randomised, crossover, isoenergetic, controlled-feeding Canola Oil Multicenter Intervention Trial II consumed three dietary oils for 6 weeks, with washout periods of ˜6 weeks between each treatment. Diets studied included a high SFA/low MUFA Control oil (36·6 % SFA/28·2 % MUFA), a conventional canola oil (6·2 % SFA/63·1 % MUFA) and a high-oleic acid canola oil (5·8 % SFA/74·7 % MUFA). No differences in fasting blood glucose were observed following the consumption of the dietary oils. However, when stratified by SCD genotypes, significant SNP-by-treatment interactions on blood glucose response were found with additive models for rs1502593 (P = 0·01), rs3071 (P = 0·02) and rs522951 (P = 0·03). The interaction for rs3071 remained significant (P = 0·005) when analysed with a recessive model, where individuals carrying the CC genotype showed an increase (0·14 (sem 0·09) mmol/l) in blood glucose levels with the Control oil diet, but reductions in blood glucose with both MUFA oil diets. Individuals carrying the AA and AC genotypes experienced reductions in blood glucose in response to all three oils. These findings identify a potential new target for personalised nutrition approaches aimed at improving glycaemic control.

Recent Clinical Trials Shed New Light on the Cardiovascular Benefits of Omega-3 Fatty Acids.

Three recent clinical trials have demonstrated the benefits of marine omega-3 fatty acids on cardiovascular disease end points. In the Vitamin D and Omega-3 Trial (VITAL), 840 mg/d of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) resulted in a 28% reduced risk for heart attacks, 50% reduced risk for fatal heart attacks, and 17% reduced risk for total coronary heart disease events. In the ASCEND trial (A Study of Cardiovascular Events in Diabetes), cardiovascular disease death was significantly reduced by 19% with 840 mg/d of EPA and DHA. However, the primary composite end points were not significantly reduced in either study. In REDUCE-IT (the Reduction of Cardiovascular Events with Icosapent Ethyl-Intervention Trial), there was a 25% decrease in the primary end point of major cardiovascular events with 4 g/d EPA (icosapent ethyl) in patients with elevated triglycerides (135-499 mg/dL) who also were taking a statin drug. For clinical practice, we now have compelling evidence of the cardiovascular benefits of omega-3 fatty acids. The findings of REDUCE-IT provide a strong rationale for prescribing icosapent ethyl for patients with hypertriglyceridemia who are on a statin. For primary prevention, the goal is to increase the population intake of omega-3 fatty acids to levels currently recommended, which translates to consuming at least one to two servings of fish/seafood per week. For individuals who prefer taking omega-3 fatty acid supplements, recent findings from clinical trials support the benefits for primary prevention.

Diets Enriched with Conventional or High-Oleic Acid Canola Oils Lower Atherogenic Lipids and Lipoproteins Compared to a Diet with a Western Fatty Acid Profile in Adults with Central Adiposity.

BACKGROUND: Novel oils high in monounsaturated fatty acids (MUFAs) and low in saturated fatty acids (SFAs) are an alternative to partially hydrogenated oils high in trans-unsaturated fatty acids. There is widespread use of high-MUFA oils across the food industry; however, limited knowledge of their cardiovascular impact exists. OBJECTIVES: We investigated the effects of diets containing canola oil, high-oleic acid canola oil (HOCO), and a control oil blend (diet formulated to emulate a Western fat profile) on lipids, lipoproteins, and apolipoproteins (apos), as secondary outcomes of the trial. METHODS: In a multi-center, double-blind, randomized, 3-period crossover, controlled feeding trial, men (n = 44) and women (n = 75) with a mean age of 44 y, mean body mass index (BMI; in kg/m2) of 31.7, and an increased waist circumference plus ≥1 metabolic syndrome criteria consumed prepared, weight-maintenance diets containing canola oil [17.5% MUFAs, 9.2% polyunsaturated fatty acids (PUFAs), 6.6% SFAs], HOCO (19.1% MUFAs, 7.0% PUFAs, 6.4% SFAs), or control oil (10.5% MUFAs, 10.0% PUFAs, 12.3% SFAs) for 6 wk with ≥4-wk washouts. Fasting serum lipids were assessed at baseline and 6 wk. Diet effects were examined using a repeated measures mixed model. RESULTS: Compared with the control, canola and HOCO diets resulted in lower endpoint total cholesterol (TC; -4.2% and -3.4%; P < 0.0001), LDL cholesterol (-6.6% and -5.6%; P < 0.0001), apoB (-3.7% and -3.4%; P = 0.002), and non-HDL cholesterol (-4.5% and -4.0%; P = 0.001), with no differences between canola diets. The TC:HDL cholesterol and apoB:apoA1 ratios were lower after the HOCO diet than after the control diet (-3.7% and -3.4%, respectively). There were no diet effects on triglyceride, HDL cholesterol, or apoA1 concentrations. CONCLUSIONS: HOCO, with increased MUFAs at the expense of decreased PUFAs, elicited beneficial effects on lipids and lipoproteins comparable to conventional canola oil and consistent with reduced cardiovascular disease risk in adults with central adiposity. This trial was registered at www.clinicaltrials.gov as NCT02029833.

Projected Long-Chain n-3 Fatty Acid Intake Post-Replacement of Vegetables Oils with Stearidonic Acid-Modified Varieties: Results from a National Health and Nutrition Examination Survey 2003-2008 Analysis.

Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) intake is well below the amount recommended by the 2015-2020 Dietary Guidelines for Americans (0.25 g/day), supporting the need for alternative dietary sources. Stearidonic acid (SDA)-enriched soybeans were bioengineered to endogenously synthesize SDA, which can be readily metabolized to EPA in humans; thus, incorporating the derived SDA-enriched soybean oil into the food supply is a potential strategy to increase EPA. We performed a dietary modeling exercise using National Health and Nutrition Examination Survey 2003-2008 repeat 24-h dietary recall data (n = 24,621) to estimate the potential contribution of SDA-enriched oils to total long-chain n-3 fatty acid intake (defined as EPA + DHA + EPA-equivalents) following two hypothetical scenarios: (1) replacement of regular soybean oil with SDA soybean oil and (2) replacement of four common vegetable oils (corn, canola, cottonseed, and soybean) with respective SDA-modified varieties. Estimated median daily intakes increased from 0.11 to 0.16 g/day post-replacement of regular soybean oil with SDA-modified soybean oil, and to 0.21 g/day post-replacement of four oils with SDA-modified oil; the corresponding mean intakes were 0.17, 0.27, and 0.44 g/day, respectively. The percent of the population who met the 0.25 g/day recommendation increased from at least 10% to at least 30% and 40% in scenarios 1 and 2, respectively. Additional strategies are needed to ensure the majority of the US population achieve EPA and DHA recommendations, and should be assessed using methods designed to estimate the distribution of usual intake of these episodically consumed nutrients.

Total Long-Chain n-3 Fatty Acid Intake and Food Sources in the United States Compared to Recommended Intakes: NHANES 2003-2008.

The American Heart Association recommends consuming fish (particularly oily fish) at least two times per week, which would provide ≈ 0.5 g/day of eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA) for cardiovascular disease risk reduction. Previous analyses indicate that this recommendation is not being met; however, few studies have assessed different ethnicities, subpopulations requiring additional n-3 fatty acid intake (i.e., children and pregnant and/or lactating women), or deciles of intake. Data from the National Health and Nutrition Examination Survey 2003-2008 was used to assess n-3 fatty acid intake from foods and supplements in the US population, according to age, sex, and ethnicity. A unique "EPA equivalents" factor, which accounts for potential conversion of shorter-chain n-3 fatty acids, was used to calculate total long-chain n-3 fatty acid intake. Data are reported for 24,621 individuals. More than 90% consumed less than the recommended 0.5 g/day from food sources (median = 0.11 g/day; mean = 0.17 g/day). Among the top 15% of n-3 fatty acid consumers, fish was the largest dietary contributor (71.2%). Intake was highest in men aged 20 years or more, and lowest in children and women who are or may become pregnant and/or are lactating. Among ethnicities, intake was lowest in Mexican-Americans. Only 6.2% of the total population reported n-3 fatty acid supplement use, and this did not alter median daily intake. Additional strategies are needed to increase awareness of health benefits (particularly among Mexican-Americans and women of childbearing age) and promote consumption of oily fish or alternative dietary sources to meet current recommendations.

Omega-3 Fatty Acids and Cardiovascular Disease: Are There Benefits?

OPINION STATEMENT: Early secondary prevention trials of fish and omega-3 polyunsaturated fatty acid (PUFA) capsules reported beneficial effects on cardiovascular disease (CVD) outcomes, including all-cause mortality and sudden cardiac death. These clinical findings, as well as observational and experimental data, demonstrated that omega-3 PUFAs reduced the risk of coronary outcomes and overall mortality and were the basis for recommendations made in the early 2000s to increase omega-3 PUFA intake. In the last 6 years, however, results from both primary and secondary prevention trials have generally failed to show a beneficial effect of omega-3 PUFA supplementation, bringing current recommendations into question. Several possible reasons for these null findings have been proposed, including short treatment periods, relatively low doses of omega-3 PUFAs, small sample sizes, higher background omega-3 intakes, and the concurrent use of modern pharmacotherapy for CVD prevention. At least one of these caveats is being assessed in major clinical trials, with two omega-3 PUFA pharmacological agents being tested at doses of 4 g/day (instead of the more common <1 g/day). These null findings, however, do not necessarily mean that omega-3 PUFAs "are ineffective" in general, only that they were not effective in the context in which they were tested. Accordingly, higher intakes of omega-3 PUFAs, either from fatty fish or from supplements, if continued for decades (as the epidemiological data support) are likely to contribute towards lower risk for CVD. At this time, evidence supports the consumption of a healthy dietary pattern with at least two servings per week of fatty fish. Omega-3 PUFA supplementation is a reasonable alternative for those who do not consume fish, although fish is the preferred source of omega-3 PUFAs because it also provides additional nutrients, some of which are often under-consumed.