Abstract
ABSTRACTThe 2015 Dietary Guidelines for Americans recommend limiting the intake of saturated fatty acids (SFAs) to <10% of energy/d and replacing dietary SFAs with unsaturated fatty acids. A Presidential Advisory from the American Heart Association recently released its evaluation of the relation between dietary fats and cardiovascular disease (CVD), and also recommended a shift from SFAs to unsaturated fatty acids, especially polyunsaturated fatty acids (PUFAs), in conjunction with a healthy dietary pattern. However, the suggestion to increase the intake of PUFAs in general, and omega-6 (n–6) PUFAs in particular, continues to be controversial. This review was undertaken to provide an overview of the evidence and controversies regarding the effects of ω-6 PUFAs on cardiometabolic health, with emphasis on risks and risk factors for CVD (coronary heart disease and stroke) and type 2 diabetes mellitus (T2D). Results from observational studies show that higher intake of ω-6 PUFAs, when compared with SFAs or carbohydrate, is associated with lower risks for CVD events (10–30%), CVD and total mortality (10–40%), and T2D (20–50%). Findings from intervention studies on cardiometabolic risk factors suggest that ω-6 PUFAs reduce concentrations of LDL cholesterol and non-HDL cholesterol in a dose-dependent manner compared with dietary carbohydrate, and have a neutral effect on blood pressure. Despite the concern that ω-6 fatty acids increase inflammation, current evidence from studies in humans does not support this view. In conclusion, these findings support current recommendations to emphasize consumption of ω-6 PUFAs as a replacement of SFAs; additional randomized controlled trials with cardiometabolic disease outcomes will help to more clearly define the benefits and risks of this policy.
Highlights
According to the AHA’s 2018 Heart Disease and Stroke Statistics Update, cardiovascular disease [CVD; including coronary artery disease (CAD), hypertension, and stroke] is the number 1 cause of death in the United States, accounting for ∼1 of every 3 deaths [1]
The review focused on the evidence considered by the Dietary Guidelines for Americans (DGA) 2015 [2] and the 2017 AHA Presidential Advisory on Dietary Fats and Cardiovascular Disease [13], new results published since that time, and an appraisal of dissenting viewpoints expressed by experts in the field of diet and cardiometabolic health
In our view, the data from randomized controlled trial (RCT) regarding the replacement of SFAs with ω-6 polyunsaturated fatty acids (PUFAs) on CVD outcomes suggest potential benefits, but are far from conclusive
Summary
According to the AHA’s 2018 Heart Disease and Stroke Statistics Update, cardiovascular disease [CVD; including coronary artery disease (CAD), hypertension, and stroke] is the number 1 cause of death in the United States, accounting for ∼1 of every 3 deaths [1]. A Presidential Advisory from the AHA recently released its evaluation of the relation between dietary fats and CVD [13] They concluded that prospective observational studies have consistently found a lower risk of CAD, as well as CVD and all-cause mortality, with lower SFA consumption and higher intakes of PUFAs or MUFAs. PUFAs include mainly omega-3 and omega-6 fatty acids. Ω-3 PUFAs, the marine-based fatty acids of EPA (20:5 ω-3 fatty acid) and DHA (22:6 ω-3 fatty acid), have been shown to possess a variety of potentially cardioprotective effects, including effects on blood lipids, hemodynamics, platelets, and fibrinolysis, and markers of inflammation and oxidative stress [14,15,16,17,18] This makes the increased consumption of ω-3 fatty acids as a replacement of SFAs an attractive approach, because the average American diet has less than the recommended intake of 8 oz seafood/wk. Despite the fact that most dietary recommendations agree that SFAs should be at least partially replaced by UFAs, in particular vegetable PUFAs, the suggestion to increase the intake of PUFAs in general, and ω-6 PUFAs in particular, continues to be controversial [2, 13, 25]
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