Polyphenol supplementation boosts aerobic endurance in athletes: systematic review.

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• Polyphenols may have specific benefits on exercise performance and metabolism in both performance and recreational athletes.
• It is important to understand that this is only seen at specific doses for sustained periods of time and compliance is essential for results.

Introduction

Extreme exercise can lead to oxidative stress in the body, which can affect muscle function and impact training and performance in athletes. Polyphenols present in plants have antioxidant properties and have emerged as potential candidates to improve exercise performance. They also promote antioxidant defences and nuclear factor erythroid 2-related factor 2 (Nrf2) signalling, which is involved in mitochondrial biogenesis. Finally, they may also alter vascular function through promoting endothelial nitric oxide synthesis, which leads to vasodilation and increased blood flow. This systematic review aimed to summarise the current research on the effects of polyphenols on endurance exercise performance.

Methods

• The inclusion criteria involved randomised control trials on healthy athletes and sports people who were supplemented with polyphenols and compared to a placebo group both before and after tests of athletic or sports performance.
• No meta-analysis was conducted.

Results

• 11 studies with 220 participants were included in the systematic review. 164 were recreational and 56 professional athletes.
• Polyphenols assessed were grape seed extract, green tea extract, olive fruit water phytocomplex, Montmorency cherry powder, carob pods, Haskap berries, Vinitrox™ (polyphenols from grape and apple), Cardiose®, and grape juice.
• Substantial improvements were seen in the time taken to complete an exercise and fatigue times.
• Mixed results were seen in time to peak power output, endurance running distance, power output, exercise intensity, rate of perceived exertion, and speed.
• Improvements were seen in flow mediated dilation and tissue oxygenation index, but only one trial was found that assessed each of these.
• Heart rate and blood pressure showed no improvements with polyphenols and mixed results were seen with VO2, VCO2 lactate level, and carbohydrate oxidation.
• Prolonged use of polyphenols were shown to promote whole body fat oxidation.
• No improvements were seen in measures of antioxidant levels but only one study looked at these.
• Long-term rather than acute polyphenol supplementation was more beneficial.

Conclusion

Polyphenols improved aerobic endurance and exercise performance. However, there is insufficient evidence to support their use for improvements to several physiological and metabolic measures.

• Practitioners may like to consider the recommendation of long-term polyphenol supplementation to healthy athletes to improve aerobic endurance and promote fat oxidation.
• 208mg of polyphenols and flavonoids in a 14.4mg per 40g in a soluble form may have optimal effects.
• However, there may be limited effects on recovery times.

• Further research could determine exercise specific dosage recommendations.