Abundant in the flavonoids anthocyanin and flavanol, blueberries have been shown in previous studies to improve cognitive performance and brain health. Steven R. McAnulty, from Appalachian State University (North Carolina, USA), and colleagues enrolled 25 men and postmenopausal women, to receive a daily supplement of blueberry powder (equivalent of 250 gm of blueberries), or placebo, for six weeks. Among those receiving the supplement, the researchers observed that natural killer cells rose by 4%. As well, among pre-hypertensive subjects, the blueberry powder caused significant reduction of diastolic blood pressure.
The study authors write that: “blueberry ingestion for six weeks increases natural killer cells and reduces augmentation index, aortic systolic pressure, and diastolic pressures in sedentary males and females.”