CARDIOVASCULAR MEDICINE

Effect of linolenic acid on cardiovascular risk markers: a systematic review

E Wendland¹, A Farmer², P Glasziou², A Neil²

¹ Graduate Studies Program in Epidemiology, Federal University of Rio Grande do Sul, Porto Alegre, Brazil
² Division of Public Health and Primary Health Care, University of Oxford, Institute of Health Sciences, Oxford, UK

Correspondence to:
Dr Andrew Farmer
Division of Public Health and Primary Care, University of Oxford, Old Road Campus, Headington, Oxford OX3 7LF, UK; andrew.farmer{at}dphpc.ox.ac.uk

Objective: To determine whether dietary supplementation with linolenic acid (ALA) can modify established and emerging cardiovascular risk markers.

Design: Systematic review and meta-analysis of randomised controlled trials identified by a search of Medline, Embase, Cochrane Controlled Trials Register (CENTRAL), and the metaRegister of Controlled Trials (mRCT).

Patients: All human studies were reviewed.

Main outcome measures: Changes in concentrations of total cholesterol, low density lipoprotein (LDL) cholesterol, high density lipoprotein (HDL) cholesterol, very low density lipoprotein (VLDL) cholesterol, triglyceride, fibrinogen, and fasting plasma glucose, and changes in body mass index, weight, and systolic and diastolic blood pressure.

Results: 14 studies with minimum treatment duration of four weeks were reviewed. ALA had a significant effect on three of the 32 outcomes examined in these studies. Concentrations of fibrinogen (0.17 µmol/l, 95% confidence interval (CI) –0.30 to –0.04, p = 0.01) and fasting plasma glucose (0.20 mmol/l, 95% CI –0.30 to –0.10, p < 0.01) were reduced. There was a small but clinically unimportant decrease in HDL (0.01 mmol/l, 95% CI –0.02 to 0.00, p < 0.01). Treatment with ALA did not significantly modify total cholesterol, triglycerides, weight, body mass index, LDL, diastolic blood pressure, systolic blood pressure, VLDL, and apolipoprotein B.

Conclusions: Although ALA supplementation may cause small decreases in fibrinogen concentrations and fasting plasma glucose, most cardiovascular risk markers do not appear to be affected. Further trials are needed, but dietary supplementation with ALA to reduce cardiovascular disease cannot be recommended.

Abbreviations: ALA, linolenic acid; CENTRAL, Cochrane Controlled Trials Register; DHA, docosahexaenoic acid; EPA, eicosapentaenoic acid; HDL, high density lipoprotein; LDL, low density lipoprotein; mRCT, metaRegister of Controlled Trials; VLDL, very low density lipoprotein

Keywords: linolenic acid; cardiovascular prevention; systematic review

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