Meta-Analysis: Omega-3 Fatty Acids Reduce Artery Stiffness

Arterial Stiffness and Cardiovascular Events

Arteries stiffen and become less flexible as a consequence of aging and arteriosclerosis. Age-related stiffness occurs when the elastic fibers within the arterial wall (elastin) begin to fray due to mechanical stress. Stiffer arteries require a greater amount of force in order to expand and take up the blood ejected from the heart. This, in turn, causes the heart to contract harder to accommodate the artery.

Arterial stiffness, in fact, has recently emerged as a significant predictor of cardiovascular disease. For example, a recent meta-analysis of 17 longitudinal studies confirmed that aortic stiffness is a significant predictor of future cardiovascular events and all-cause mortality (1). Thus, evidence-based approaches to reducing arterial stiffness are of significant clinical importance.

Omega-3 Fatty Acids and Arterial Flexibility

One candidate for helping to alleviate arterial stiffness is the omega-3 fatty acids found in fish oil – EPA and DHA. Fish oils have long been known to mildly reduce elevated blood pressure, and evidence suggests that they may lower heart rate and prevent arrhythmia. They are also known to benefit those with coronary heart disease by reducing mortality. But do they have an effect on arterial stiffness?

Although current evidence from randomized and controlled human clinical trials suggests that fish oils may be beneficial in reducing arterial stiffness, no quantitative synthesis of this data has been conducted. This gap in knowledge led a team of researchers from Melbourne, Australia to conduct the first systematic review and meta-analysis of controlled trials to assess whether fish oils are of benefit in arterial stiffness (2).

Study Design

Multiple databases and clinical trial registries were systematically searched up until September 2010 for randomized and controlled adult human clinical trials to investigate the effects of long-chain n-3 fatty acids on arterial stiffness. No limits were set on dosage sizes or sample characteristics.

A total of 10 omega-3 trials met the final inclusion criteria; 4 using pulse wave velocity and 6 using arterial compliance, measured as capacitive compliance or systemic arterial compliance, as respective outcome measures.

Results

Meta-analysis revealed that omega-3 was statistically significant in effectively improving both pulse wave velocity (P<0.01) and arterial compliance (P<0.001). There was no evidence of heterogeneity or publication bias. Results were not influenced by changes in blood pressure, heart rate or BMI.

Comments

The findings of the present analysis suggest that high dose supplementation with EPA and DHA offers a scientifically supported means of reducing arterial stiffness, and may account for some of the cardio-protective effects of these omega-3 fatty acids, according to the authors.

One possible limitation of this analysis is that none of the studies included used carotid-femoral pulse wave velocity, which is regarded as the ‘gold standard’ in the measurement of arterial stiffness. However, the measures used in the present meta-analysis such as brachial-ankle pulse wave velocity and systemic arterial compliance are also valid and predictive of CVD and or mortality.

In terms of any potential impact on ocular health, associations between arterial stiffness and AMD and arterial stiffness and glaucoma have been reported in some epidemiologic investigations, though not others.

References

1. Vlachopoulos C, et al. Prediction of cardiovascular events and all-cause mortality with arterial stiffness. A systematic review and meta-analysis. Journal of American College of Cardiology 55:1318–27, 2010.
2. Pase M, et al. Review Article. Do long-chain n-3 fatty acids reduce arterial stiffness? A meta-analysis of randomised controlled trials. British Journal of Nutrition, Epub July 6, 2011.