Journal Article

The effect of replacing saturated fat with mostly n-6 polyunsaturated fat on coronary heart disease: a meta-analysis of randomised controlled trials

Hamley, Steven

2017

Overview

Background A cornerstone of conventional dietary advice is the recommendation to replace saturated fatty acids (SFA) with mostly n-6 polyunsaturated fatty acids (PUFA) to reduce the risk of coronary heart disease (CHD). Many clinical trials aimed to test this advice and have had their results pooled in several meta-analyses. However, earlier meta-analyses did not sufficiently account for major confounding variables that were present in some of those trials. Therefore, the aim of the study was to account for the major confounding variables in the diet heart trials, and emphasise the results from those trials that most accurately test the effect of replacing SFA with mostly n-6 PUFA. Design Clinical trials were identified from earlier meta-analyses. Relevant trials were categorised as ‘adequately controlled’ or ‘inadequately controlled’ depending on whether there were substantial dietary or non-dietary differences between the experimental and control groups that were not related to SFA or mostly n-6 PUFA intake, then were subject to different subgroup analyses. Results When pooling results from only the adequately controlled trials there was no effect for major CHD events (RR = 1.06, CI = 0.86–1.31), total CHD events (RR = 1.02, CI = 0.84–1.23), CHD mortality (RR = 1.13, CI = 0.91–1.40) and total mortality (RR = 1.07, CI = 0.90–1.26). Whereas, the pooled results from all trials, including the inadequately controlled trials, suggested that replacing SFA with mostly n-6 PUFA would significantly reduce the risk of total CHD events (RR = 0.80, CI = 0.65–0.98, P  = 0.03), but not major CHD events (RR = 0.87, CI = 0.70–1.07), CHD mortality (RR = 0.90, CI = 0.70–1.17) and total mortality (RR = 1.00, CI = 0.90–1.10). Conclusion Available evidence from adequately controlled randomised controlled trials suggest replacing SFA with mostly n-6 PUFA is unlikely to reduce CHD events, CHD mortality or total mortality. The suggestion of benefits reported in earlier meta-analyses is due to the inclusion of inadequately controlled trials. These findings have implications for current dietary recommendations.

• Publisher: BioMed Central,Springer Nature B.V,BMC
• Subject: Cardiovascular disease / Cardiovascular diseases / Cholesterol - blood / Clinical Nutrition / Clinical trial / Clinical trials / Coronary artery disease / coronary disease / Coronary Disease - epidemiology / Coronary Disease - mortality / Coronary heart disease / Diet / Diet heart hypothesis / Dietary Fats / dietary recommendations / Fatty Acids - administration & dosage / Fatty Acids - blood / Fatty Acids, Omega-6 - administration & dosage / Fatty Acids, Omega-6 - blood / Health Promotion and Disease Prevention / Health risk assessment / heart / Heart diseases / Humans / Low density lipoprotein / Medicine / Medicine & Public Health / Meta-analysis / Mortality / Nutrition / Observational Studies as Topic / Omega 6 / omega-6 fatty acids / Polyunsaturated fat / Polyunsaturated fatty acids / randomized clinical trials / Randomized Controlled Trials as Topic / Review / Risk Factors / risk reduction / Saturated fat / saturated fats / saturated fatty acids / unsaturated fats / Xenografts