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 Dec;104(11):1586-600. doi: 10.1017/S0007114510004010.

Abstract

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.

Publication types

  • Meta-Analysis
  • Research Support, N.I.H., Intramural

MeSH terms

  • Coronary Disease / etiology
  • Coronary Disease / mortality
  • Coronary Disease / prevention & control*
  • Dietary Fats / administration & dosage*
  • Fatty Acids, Omega-3 / therapeutic use*
  • Fatty Acids, Omega-6 / adverse effects
  • Fatty Acids, Omega-6 / therapeutic use*
  • Humans
  • Linoleic Acid / administration & dosage
  • Myocardial Infarction / etiology
  • Myocardial Infarction / prevention & control*
  • Randomized Controlled Trials as Topic
  • Risk Factors

Substances

  • Dietary Fats
  • Fatty Acids, Omega-3
  • Fatty Acids, Omega-6
  • Linoleic Acid