Latest Science

Should performers harness the power of berries?

March 11, 2014

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.

Main findings

  • Consuming 375g of blueberries 1 hour before exercise reduced measures of oxidative stress, as demonstrated by a smaller rise of plasma F2-isoprostanes and lesser modification of RNA in urine, and increased levels of anti-inflammatory cytokine IL-10, in comparison to the control group.
  • The men that consumed an additional 250g of blueberries each day for 6 weeks had a significantly higher natural killer cell count than those that did not consume blueberries.

Significant methodology

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.

Take home message

Consuming blueberries (albeit a large portion!) before training appears to reduce exercise-induced oxidative stress and inflammation. Furthermore, previous research has shown that antioxidant supplementation (using different antioxidant fruits) may reduce muscle damage following heavy training.

But a word of caution: there is currently huge debate over whether a reduction in oxidative stress during exercise is beneficial or detrimental to long term training adaptations.

At present, chronic supplementation during training should be avoided. Performers might however, consider utilising antioxidants during repeated periods of competition, when reducing metabolic stress and maintaining muscle function may improve performance.

© Performance Nutrition 2016