NK cells levels increased by about 4% after six weeks of daily supplementation with the equivalent of 250 grams of blueberries, compared to placebo, according to findings published in Nutrition Research.
“As a demonstration of the potential of berries to modulate the immune system, we have observed significant increases in NK cells in highly fit athletes after 6-wks of 250g per day of whole blueberries. Interestingly, this difference was maintained throughout a 2.5 hour treadmill run versus non-supplemented subjects,” wrote researchers from the Appalachian State University in Boone, North Carolina.
“To our knowledge, our studies represent the first to investigate the effect of blueberry ingestion directly on NK cell counts in humans.”
The US Highbush Blueberry Council provided the blueberry powder used in the supplements, which were produced by Mercer Foods, while Van Drunen/FutureCeuticals produced the placebos.
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.
The new study, led by Professor Steven McAnulty from ASU’s Department of Health and Exercise Science, supports the potential heart health benefits of the berries. Data from 25 men and postmenopausal women indicated that aortic systolic pressures were significantly decreased in the participants receiving the blueberry powder supplements, compared with placebo.
In addition, participants who were classified as pre-hypertensive, defined as blood pressures over 120/80 mmHg, exhibited significant decreases in diastolic pressure after six weeks of supplementation, compared to baseline values.
“We accept our hypothesis that daily blueberry consumption increases natural killer cells and reduces augmentation index and central pulse wave velocity,” wrote the researchers. “However, we reject our hypothesized increase in redox capacity and reduction of aortic systolic pressure and overall blood pressures.
“Future investigations should aim for determining thresholds of timing of ingestion and quantity of berries that must be ingested for these positive changes to occur.”
Source: Nutrition Research
Published online ahead of print, doi: 10.1016/j.nutres.2014.07.002
“Six weeks daily ingestion of whole blueberry powder increases natural killer cell counts and reduces arterial stiffness in sedentary males and females”
Authors: L.S. McAnulty, S.R. Collier, M.J. Landram, D.S. Whittaker, S.E. Isaacs, J.M. Klemka, S.L. Cheek, J.C. Arms, S.R. McAnulty