A small study involving 48 post-menopausal women with pre- and stage 1 hypertension found that daily consumption of freeze-dried blueberry powder for eight weeks improved blood pressure and arterial stiffness. The amount of powder (22g) equated to one cup of fresh blueberries.
The improvement is thought to occur partly by helping nitric oxide-mediated vasodilation. Nitric oxide bioavailability is believed to increase endothelial-dependent vasodilation, leading to lower blood pressure.
After eight weeks those taking the blueberry powder showed a mean systolic blood pressure that was lower by 7 mmHg (5.1%) and mean diastolic blood pressure lower by 5 mmHg (6.3%), with no corresponding lowering in those taking a placebo. Nitric oxide measurements were significantly increased (68.5%) in the blueberry group. Arterial stiffness, measured by brachial ankle pulse wave velocity was significantly reduced (6.5%) after eight weeks in the blueberry-treated group, with, again, no changes in the control group. Aortic stiffness, measured by the carotid-femoral pulse wave velocity, did not change in either group, suggesting that peripheral arteries may be more responsive to dietary interventions than central arteries.
Among all fruits, blueberries are one of the richest sources of phenolic compounds. While previous studies have found positive effects on cardiovascular risk factors, they have all used large amounts of blueberry powder. These findings suggest that regular consumption of blueberries in quite moderate amounts could prevent or delay the progression of prehypertension to hypertension.
Johnson, S. A., Figueroa, A., Navaei, N., Wong, A., Kalfon, R., Ormsbee, L. T., … Arjmandi, B. H. (2015). 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. Journal of the Academy of Nutrition and Dietetics, 115(3), 369–377. http://doi.org/10.1016/j.jand.2014.11.001