Effect of alpha-linolenic acid on cardiovascular risks markers: a systematic review

Eliana Wendland ¹, Andrew J Farmer ^2*, Glasziou Paul ³ and Andrew Neil ³

¹ Federal University of Rio Grande do Sul, Porto Alegre, Brazil
² University of Oxford, Division of Public Health and Primary Care, University of Oxford, United Kingdom
³ Division of Public Health and Primary Care, University of Oxford, United Kingdom

^* To whom correspondence should be addressed. E-mail: andrew.farmer{at}dphpc.ox.ac.uk.

Accepted 4 May 2005

Abstract

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

Design: Systematic review and meta-analysis of randomised controlled trials.

Setting: MEDLINE, Embase, Cochrane register of controlled trials and the metaRegister of controlled trials were searched.

Patients: All studies carried out in humans were included in the review.

Main outcome measures: Total cholesterol, LDL cholesterol, HDL cholesterol, VLDL cholesterol, triglyceride, fibrinogen and fasting plasma glucose, changes in body mass index, weight, and systolic and diastolic blood pressure.

Results: Fourteen studies with minimum treatment duration of 4 weeks were included. ALA had a significant effect on three of the 32 outcomes examined in these studies reducing the levels of fibrinogen (0.17 µmol/l [95% 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), and there was a small but clinically unimportant increase in high-density lipoprotein (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, low-density lipoprotein, diastolic blood pressure, systolic blood pressure, very low-density lipoprotein (VLDL) and apolipoprotein-B.

Conclusions: Although ALA supplementation may causes small decreases in fibrinogen levels and fasting plasma glucose, there appears to be no effect on most cardiovascular risk markers. Further trials are needed, but dietary supplementation with ALA to reduce cardiovascular disease cannot currently be recommended.

Keywords: alpha-linolenic acid, cardiovascular risk factors, meta-analysis, systematic review

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