So-called ‘superfoods’, such as blueberries, are currently generating a great deal of interest due to their potential to improve health. Whilst the majority of new research looks to access the impact of these nutrient-dense foods on general health and disease risk, a new study by Dr Lisa McAnulty and colleagues has investigated the effect of habitual and acute ingestion of blueberries on responses to exercise training.
The study found that consuming blueberries before exercise suppressed levels of oxidative stress during exercise. Blueberries and other berries, such as cranberries and blackberries, are rich in flavonoids, which have powerful antioxidant properties. Antioxidants are known to reduce oxidative damage and destruction of cells due to their ability to neutralise reactive oxygen species.
Interestingly it was also found that the performers that consumed a daily intake of blueberries for 6 weeks had a higher number of natural killer cells in their blood. Natural killer cells, a type of white blood cell, play a major role in the innate and adaptive immune systems. Although this is an exciting finding, additional studies are required to substantiate any relationship between the intake of blueberries and host immunity.
Twenty-five males completed the study. Thirteen were placed in the blueberry (BB) group and twelve in the control (C) group. Both groups were asked to follow their normal diet for 6 weeks however the BB group were asked to consume an additional 250g of blueberries each day. After the 6 weeks the men reported to back to the lab where they performed a 2.5 hour treadmill run at ~72% VO2max. One hour before completing the run the BB group only, consumed 375g of blueberries. Blood and urine samples were taken pre-exercise, immediately post-exercise and 1 hour post-exercise. Muscle biopsies were taken from the vastus lateralis muscle, pre-exercise and immediately post-exercise. Samples were analysed for a variety of measures to access oxidative stress, inflammation and immune function.