Blueberries could lower blood pressure: RCT data
Results from the randomised, double-blind, placebo controlled trial, showed that consumption of blueberries for eight weeks significantly reduced blood pressure measures in postmenopausal women with pre- and stage 1-hypertension (high blood pressure).
Writing in the Journal of the Academy of Nutrition and Dietetics, the US-based research team randomly assigned 48 women to receive either 22 grams of freeze-dried blueberry powder or 22 grams of a control powder every day for eight weeks – finding that blueberry consumption may reduce blood pressure and arterial stiffness.
"These findings suggest that blueberries may prevent the progression to full-blown hypertension,” said corresponding author Professor Bahram H. Arjmandi of Florida State University.
"The changes in blood pressure noted in this study are of clinical significance as they demonstrate that blood pressure can be favourably altered by the addition of a single dietary component (e.g. blueberries)," added lead author, Dr Sarah Johnson.
"Considering the prevalence of HTN [hypertension] in … preventive strategies such as dietary modifications (e.g. functional foods and dietary supplements) that aim to improve HTN and its related complications are warranted."
The team noted that although the prevalence of HTN is associated with aging in both sexes, the increased incidence of high blood pressure, particularly systolic blood pressure (SBP), in women after menopause exceeds that of men.
Forty-eight women with pre- and stage 1-HTN who met all inclusion criteria were recruited to participate in the eight-week, randomised, double-blind, placebo-controlled clinical trial.
Johnson and her colleagues found that consumption of freeze-dried blueberry powder - equating to one cup of fresh blueberries per day - into the diet improved blood pressure and arterial stiffness potentially through enhanced nitric oxide (NO)-mediated vasodilation.
At the conclusion of the study, mean SBP was lower by 5.1% and mean diastolic blood pressure (DBP) was lower by 6.3% in the subjects in the blueberry group, with no corresponding lowering in the placebo group.
In addition, NO measurements were significantly increased in the blueberry group, rising from 9.11 to 15.35 μM - with no change in the control group.
Brachial ankle pulse wave velocity (baPWV), which is a composite measure of central (aortic) and peripheral arterial stiffness, was significantly reduced after eight weeks in the blueberry-treated group, whereas there were no changes in the control group, said the team. However, they noted that carotid-femoral pulse wave velocity (cfPWV), the best measure of aortic stiffness, did not change in either group.
Johnson and colleagues commented that this finding suggests that peripheral arteries may be more responsive to dietary interventions than central arteries.
Source: Journal of the Academy of Nutrition and Dietetics
Published online ahead of print, doi: 10.1016/j.jand.2014.11.001
“Daily Blueberry Consumption Improves Blood Pressure and Arterial Stiffness in Postmenopausal Women with Pre- and Stage 1-Hypertension: A Randomized, Double-Blind, Placebo-Controlled Clinical Trial”
Authors: Sarah A. Johnson, Arturo Figueroa, et al