Six weeks daily ingestion of whole blueberry powder increases natural killer cell counts and reduces arterial stiffness in sedentary males and females

Evidence suggests that berries contain bioactive compounds, which reduce certain cancers and hypertension. Our hypothesis was that daily blueberry (BB) consumption would increase natural killer (NK) cells and plasma redox capacity and reduce blood pressure, augmentation index (AIx), central pulse wave velocity, and aortic systolic pressures (ASPs). Twenty-five men and postmenopausal women aged 18 to 50 years were recruited and randomized to BB (n, 13) or placebo groups (n, 12). Participants were provided with BB (equivalent to 250 g berries) or placebo powders each day for 6 weeks. Blood pressure, vascular performance testing, and blood samples were taken at baseline (presupplementation). Participants returned after 6 weeks and repeated all procedures. Presupplementation to postsupplementation comparisons for the main effects of treatment, time, and treatment-time interaction were made using a 2 (treatment) × 2 (times) repeated-measures analysis of variance for all vascular measures, redox status, and NK cell counts. Anthropometric measures were compared using t tests. Body mass, composition, and overall blood pressures were not affected in either group. Overall, AIx and ASPs were decreased in BB (treatment effect, P = .024 and P = .046, respectively). Plasma redox was not affected. Absolute NK cells were increased in BB (time, P = .001 and interaction, P = .012). Subjects (n, 9) with prehypertensive pressures (≥120/80 mm Hg, respectively) were examined as a subset using t tests and exhibited significant reductions in diastolic pressure (P = .038) from presupplementation to postsupplementation in BB. We conclude that BB ingestion for 6 weeks increases NK cells and reduces AIx, ASP, and diastolic pressures in sedentary males and females.