Omega‐3 fatty acids for intermittent claudication
Abstract
Background
Omega‐3 fatty acids are established as being effective in the treatment and prevention of coronary artery disease. It is possible that they may also benefit people with peripheral arterial disease, since the pathogenesis of the two conditions is similar.
Objectives
To determine the clinical and haematological effects of omega‐3 supplementation in people with intermittent claudication.
Search methods
Trials were identified from the Cochrane Peripheral Vascular Diseases Group Specialised Register (last searched August 2007), and the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library (last searched Issue 3, 2007). In addition, we searched literature from pharmaceutical companies, manufacturers of omega‐3 rich foods and web sites of nutritional organisations dedicated to omega‐3 fatty acids.
Selection criteria
Randomised controlled trials of omega‐3 fatty acids versus placebo or non‐omega‐3 fatty acids in people with intermittent claudication.
Data collection and analysis
One author identified potential trials. Two authors independently assessed trial quality and extracted data. We contacted study authors for additional information if necessary.
Main results
Six studies were included representing 313 participants. All studies compared omega‐3 fatty acid supplementation with placebo lasting from 4 weeks to 2 years. Two studies with long treatment periods administered additional substances, making any observed effects impossible to attribute to omega‐3 fatty acids and were therefore excluded from the statistical analyses.
No significant differences between intervention and control groups were observed in ankle brachial pressure index (ABPI) (weighted mean difference (WMD) ‐0.02; 95% CI ‐0.09 to 0.05), systolic blood pressure (WMD 5.00 mmHg; 95% CI ‐11.59 to 21.59), plasma viscosity (WMD 0.03 mPa/s; 95% CI ‐0.02 to 0.08), pain‐free walking distance (PFWD) (WMD 7.46 m; 95% CI ‐25.47 to 40.39), or maximal walking distance (MWD) (WMD 0.27 m; 95% CI ‐39.59 to 40.13).
Blood viscosity levels decreased. Gastrointestinal side effects were observed in two studies. Omega‐3 fatty acid supplementation increased (low‐density lipoprotein) LDL cholesterol levels (WMD 0.80 mmol/litre; 95% CI 0.34 to 1.26) and total cholesterol levels (WMD 0.64 mmol/litre; 95% CI 0.08 to 1.20).
Authors' conclusions
Omega‐3 fatty acids appear to have limited haematological benefits in people with intermittent claudication but there is no evidence of consistent improved clinical outcomes which are the primary outcomes of this review (quality of life, PFWD, MWD, ABPI, angiographic findings). Supplementation may also cause adverse effects such as increased total and LDL cholesterol levels. Further research is needed in this area, to evaluate short‐ and long‐term effects on more clinically relevant outcomes.
PICOs
Plain language summary
Omega‐3 fatty acid supplementation for intermittent claudication
Intermittent claudication is a tightening sensation in the calf due to a lack of blood needed to supply those muscles with oxygen during exercise or movement, ultimately resulting in the patient to slow or stop movement. It is the most common presenting symptom for people with chronic lower limb arterial disease resulting from atherosclerosis due to a narrowing of the arteries that supply the lower limbs with blood. People with mild lower limb arterial disease are advised to stop smoking, exercise, and take low‐dose aspirin to prevent heart attack or stroke. There is no widely accepted medication to treat claudication.
Omega‐3 fatty acids are polyunsaturated fatty acids found in fish oils, eggs, fruits and vegetables. They are essential nutrients in that the body cannot synthesize omega‐3 fatty acids de novo.
The review included six studies representing a total of 313 participants, comparing omega‐3 fatty acid supplementation with other fatty acids. On the basis of these studies, omega‐3 fatty acid supplementation did not improve ankle brachial pressure index or walking distance. Blood viscosity was also reduced with seven weeks to two years of supplementation. There appear to be some haematological benefits but there is little evidence for improved clinical outcomes. Notably, LDL cholesterol and total cholesterol were slightly increased after omega‐3 fatty acid supplementation with four week to four months supplementation.
The benefits of omega‐3 fatty acids must be considered in light of potential increases in blood cholesterol levels.
