A Cochrane review [Abstract] 1 included 9 studies with a total of 425 subjects. All studies compared omega-3 fatty acid supplementation with placebo lasting from 4 weeks to 2 years. Three studies with long treatment periods administered additional substances, making any observed effects impossible to attribute to omega-3 fatty acids and were excluded from the statistical analyses.
No significant differences between intervention and control groups were observed in pain-free walking distance (MD 11.62 m, 95% CI -67.74 to 90.98), maximal walking distance (MD 16.99 m, 95% CI -72.14 to 106.11), ankle brachial pressure index (MD -0.02, 95% CI -0.09 to 0.05), total cholesterol levels (MD 0.27 mmol/L, 95% CI -0.48 to 1.01), high-density lipoprotein cholesterol levels (MD 0.00 mmol/L, 95% CI -0.16 to 0.15), low-density lipoprotein cholesterol levels (MD 0.44 mmol/L, 95% CI -0.31 to 1.19), triglyceride levels (MD -0.39 mmol/L, 95% CI -1.10 to 0.33), systolic blood pressure (MD 5.00 mmHg, 95% CI -11.59 to 21.59) or plasma viscosity (MD 0.03 mPa/s, 95% CI -0.02 to 0.08).
There was some limited evidence that blood but not plasma viscosity levels decreased with treatment and gastrointestinal side effects such as nausea, diarrhoea and flatulence were observed in two studies.
Comment: The quality of evidence is downgraded by study limitations (inadequate follow up and active placebo: oleic acid and linoleic acid used as placebo), by imprecise results (limited study size for each comparison) and by heterogeneity (variability in results across studies).
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