Eight weeks of consuming a daily dose of 22 grams of freeze-dried blueberry powder resulted in 5.1% and 6.3% reductions in systolic and diastolic blood pressure, wrote the researchers in the Journal of the Academy of Nutrition and Dietetics .
The benefits were linked to an increase in levels of nitric oxide, which were found to increase from 9.11 to 15.35 micromoles over the course of the study. NO is a potent vasodilator, helping to relax the walls of blood vessels and lower blood pressure.
“To our knowledge, this is the first study to evaluate the effects of blueberries on arterial function as was done in this study, as well as in this study population,” said corresponding author Bahram Arjmandi, PhD. “These findings suggest that blueberries may prevent the progression to full-blown hypertension.”
“Considering the prevalence of hypertension in the US, preventive strategies such as dietary modifications (e.g. functional foods and dietary supplements) that aim to improve hypertension and its related complications are warranted.”
The beneficial effects of the blueberries are thought to be linked to their flavonoid content - in particular anthocyanins and flavanols.
Consumer interest in blueberries and the compounds they contain has increased in recent years, following results from studies reporting a wide range of health benefits, most notably for brain health and reducing the risk of cognitive decline.
“Compelling” data published recently in the American Journal of Clinical Nutrition indicated that blueberry flavonoids could boost endothelial function and enhance heart health.
Endothelial dysfunction may play an important role in the increases in blood pressure that occur after menopause. Further, endothelial dysfunction is known to increase arterial stiffness, which is involved in the development and progression of both hypertension and cardiovascular disease.
The Florida State researchers recruited 48 women to participate in their eight-week, randomized, double-blind, placebo-controlled clinical trial. Participants were randomly assigned to receive either 22 grams per day of freeze-dried blueberry powder or 22 grams of a control powder for eight weeks. This dose was equivalent to one cup of fresh blueberries.
The data showed that the blueberry powder was associated with significant reductions in systolic and diastolic blood pressure.
“The changes in blood pressure noted in this study are of clinical significance as they demonstrate that blood pressure can be favorably altered by the addition of a single dietary component (e.g. blueberries),” said lead author Sarah Johnson, PhD.
In addition, improvements in brachial-ankle pulse wave velocity were also reported. Pulse wave velocity is a non-invasive method for assessing arterial stiffness and has been shown to predict future cardiovascular events. In the current study, 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.
On the other hand, carotid-femoral pulse wave velocity (cfPWV), the best measure of aortic stiffness, did not change in either group. This suggests that peripheral arteries may be more responsive to dietary interventions than central arteries.
“This [study] suggests that regular consumption of blueberries over the long term could potentially delay the progression of hypertension and reduce cardiovascular risk in postmenopausal women,” concluded the researchers.
The study was supported by the US Highbush Blueberry Council and the US Department of Agriculture.
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: S.A. Johnson, A. Figueroa, N. Navaei, et al.