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Review
. 2017 May 19;16(1):30.
doi: 10.1186/s12937-017-0254-5.

The Effect of Replacing Saturated Fat With Mostly n-6 Polyunsaturated Fat on Coronary Heart Disease: A Meta-Analysis of Randomised Controlled Trials

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Free PMC article
Review

The Effect of Replacing Saturated Fat With Mostly n-6 Polyunsaturated Fat on Coronary Heart Disease: A Meta-Analysis of Randomised Controlled Trials

Steven Hamley. Nutr J. .
Free PMC article

Abstract

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.

Keywords: Clinical trial; Coronary heart disease; Diet heart hypothesis; Meta-analysis; Omega 6; Polyunsaturated fat; Randomised controlled trial; Saturated fat.

Figures

Fig. 1
Fig. 1
Forest plot showing pooled RR with 95% CI for the number of major CHD events
Fig. 2
Fig. 2
Forest plot showing pooled RR with 95% CI for the number of total CHD events
Fig. 3
Fig. 3
Forest plot showing pooled RR with 95% CI for CHD mortality
Fig. 4
Fig. 4
Forest plot showing pooled RR with 95% CI for total mortality

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References

    1. Siri-Tarino PW, Sun Q, Hu FB, Krauss RM. Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease. Am J Clin Nutr. 2010;91:535–546. doi: 10.3945/ajcn.2009.27725. - DOI - PMC - PubMed
    1. Ramsden CE, Hibbeln JR, Majchrzak SF, Davis JM. N-6 fatty acid-specific and mixed polyunsaturate dietary interventions have different effects on chd risk: a meta-analysis of randomised controlled trials. Br J Nutr. 2010;104:1586–1600. doi: 10.1017/S0007114510004010. - DOI - PubMed
    1. Chowdhury R, Warnakula S, Kunutsor S, Crowe F, Ward HA, Johnson L, et al. Association of dietary, circulating, and supplement fatty acids with coronary risk: a systematic review and meta-analysis. Ann Intern Med. 2014;160:398–406. doi: 10.7326/M13-1788. - DOI - PubMed
    1. Harcombe Z, Baker J, Cooper S, Davies B, Sculthorpe N, DiNicolantonio J, et al. Evidence from randomised controlled trials did not support the introduction of dietary fat guidelines in 1977 and 1983: A systematic review and meta-analysis. Open Heart. 2015;2:e000196. - PMC - PubMed
    1. Ramsden CE, Zamora D, Majchrzak-Hong S, Faurot KR, Broste SK, Frantz RP, et al. Re-evaluation of the traditional diet-heart hypothesis: Analysis of recovered data from minnesota coronary experiment (1968–73) BMJ. 2016;353:i1246. doi: 10.1136/bmj.i1246. - DOI - PMC - PubMed
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