Low doses of the omega-3 fatty acids docosahexaenoic acid (DHA) successfully reduced diastolic blood pressure by 3.3 mmHg in a clinical trial, backing up previous results with higher doses. //
"A significant reduction in diastolic BP was noted which is likely to be of clinical significance with regard to risk of future vascular events in middle-aged subjects," wrote lead author Hannah Theobald from King's College London.
Omega-3 has been identified as one of the super-nutrients taking the food and supplements industry by storm. Much of its healthy reputation that is seeping into consumer consciousness is based largely on evidence that it can aid cognitive function and may help protect the heart against cardiovascular disease.
Several intervention trials have reported positive benefits on blood pressure and cardiovascular disease using omega-3 fatty acids. Indeed, Theobald noted that a meta-analysis of randomized, controlled trials showed significant decreases in both systolic and diastolic blood pressure with omega-3 doses in the region of two to three grams per day.
To test if lower doses also conferred a positive effect, the King's College researchers recruited 38 middle-aged subjects (average age 48.6, average BMI 24 kg per sq.m, baseline average blood pressure 121.6/79.15 mmHg) to randomly receive either a 0.7 gram daily dose of DHA derived from Crypthecodinium cohnii (Martek Biosciences) or an olive oil placebo for three months. A four-month washout period separated the cross-over to the alternative intervention.
Writing in the current issue of the Journal of Nutrition Theobald states that the daily DHA supplement increased DHA levels in red blood cells (erythrocytes) by 58 per cent.
Diastolic blood pressure decreased by an average of 3.3 mmHg, while no significant differences occurred for systolic blood pressure, she said.
Other measures of cardiovascular function, like the markers o
f inflammation, C-reactive protein and interleukin-6 (IL-6), were not affected significantly by supplemental DHA.
The potential mechanism behind these effects was not studied directly, but the researchers state that other studies have proposed a direct effect of the omega-3 fatty acids on the electrophysiology of the heart by affecting the sinus node (the heart's natural pacemaker) or efficiency of the ventricles.
"Future work is needed to confirm these findings and to investigate further the effects of DHA on cardiac function," concluded the researchers.
Hypertension, defined as having a systolic and diastolic BP greater than 140 and 90 mmHg, affects about 600 million people worldwide and is associated with over seven million deaths.
Commenting independently on the study, June Davidson, a cardiac nurse from UK charity, the British Heart Foundation (BHF) told NutraIngredients.com: "This study shows that low dose supplements with long chain omega-3 can lower diastolic blood pressure. However we need further research to show whether such low doses could reduce cardiovascular events, such as heart attacks or strokes.
"Diets rich in long chain omega-3 fats are beneficial for heart health. The best source of these omega -3s is oily fish, such as mackerel, sardines, salmon, trout and fresh tuna."
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