Journal Article

n-6 Fatty acid-specific and mixed polyunsaturate dietary interventions have different effects on CHD risk: a meta-analysis of randomised controlled trials

Majchrzak, Sharon F., Ramsden, Christopher E., Hibbeln, Joseph R., Davis, John M.

2010

Overview

Randomised controlled trials (RCT) of mixed n-6 and n-3 PUFA diets, and meta-analyses of their CHD outcomes, have been considered decisive evidence in specifically advising consumption of ‘at least 5–10 % of energy as n-6 PUFA’. Here we (1) performed an extensive literature search and extracted detailed dietary and outcome data enabling a critical examination of all RCT that increased PUFA and reported relevant CHD outcomes; (2) determined if dietary interventions increased n-6 PUFA with specificity, or increased both n-3 and n-6 PUFA (i.e. mixed n-3/n-6 PUFA diets); (3) compared mixed n-3/n-6 PUFA to n-6 specific PUFA diets on relevant CHD outcomes in meta-analyses; (4) evaluated the potential confounding role of trans-fatty acids (TFA). n-3 PUFA intakes were increased substantially in four of eight datasets, and the n-6 PUFA linoleic acid was raised with specificity in four datasets. n-3 and n-6 PUFA replaced a combination of TFA and SFA in all eight datasets. For non-fatal myocardial infarction (MI)+CHD death, the pooled risk reduction for mixed n-3/n-6 PUFA diets was 22 % (risk ratio (RR) 0·78; 95 % CI 0·65, 0·93) compared to an increased risk of 13 % for n-6 specific PUFA diets (RR 1·13; 95 % CI 0·84, 1·53). Risk of non-fatal MI+CHD death was significantly higher in n-6 specific PUFA diets compared to mixed n-3/n-6 PUFA diets (P = 0·02). RCT that substituted n-6 PUFA for TFA and SFA without simultaneously increasing n-3 PUFA produced an increase in risk of death that approached statistical significance (RR 1·16; 95 % CI 0·95, 1·42). Advice to specifically increase n-6 PUFA intake, based on mixed n-3/n-6 RCT data, is unlikely to provide the intended benefits, and may actually increase the risks of CHD and death.

• Publisher: Cambridge University Press
• Subject: Biological and medical sciences / cardiovascular diseases / Clinical trials / Coronary Disease - etiology / Coronary Disease - mortality / Coronary Disease - prevention & control / Diet / diet-related diseases / dietary fat / Dietary Fats - administration & dosage / Fatty acids / Fatty Acids, Omega-3 - therapeutic use / Fatty Acids, Omega-6 - adverse effects / Fatty Acids, Omega-6 - therapeutic use / Feeding. Feeding behavior / Fundamental and applied biological sciences. Psychology / human diseases / human nutrition / Humans / Linoleic acid / Linoleic Acid - administration & dosage / Meta-analysis / Mortality / Myocardial infarction / Myocardial Infarction - etiology / Myocardial Infarction - prevention & control / n-6 Fatty acids / nutritional intervention / omega-3 fatty acids / omega-6 fatty acids / polyunsaturated fatty acids / PUFA / Randomised controlled trials / randomized clinical trials / Randomized Controlled Trials as Topic / relative risk / Risk Factors / Risk reduction / trans fatty acids / Vertebrates: anatomy and physiology, studies on body, several organs or systems