Plain language summary
Prolonged high-intensity endurance training and competition can lead to exercise-induced fatigue, muscle function decline, and oxidative stress. Natural plant extracts, including polyphenols, have gained attention for their potential to enhance athletic performance and aid recovery. This study aimed to examine the role of polyphenol supplementation in improving aerobic endurance among athletes and individuals with regular exercise habits. This study was a systematic review of 11 studies, focusing on the impact of polyphenols on aerobic endurance. Results showed that flavonoid-rich compounds, providing 208 mg of polyphenols and 14.4 mg of flavonoids per 40 g in a water-soluble form, showed the most noticeable improvement in exercise performance during a 6-week supplementation period. Authors concluded that even though polyphenol supplementation demonstrated enhancements in several indicators of aerobic endurance exercise performance, it’s essential to interpret these findings cautiously due to the limited number of available studies.
Expert Review
Conflicts of interest:
None
Take Home Message:
- 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.
Evidence Category:
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X
A: Meta-analyses, position-stands, randomized-controlled trials (RCTs)
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B: Systematic reviews including RCTs of limited number
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C: Non-randomized trials, observational studies, narrative reviews
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D: Case-reports, evidence-based clinical findings
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E: Opinion piece, other
Summary Review:
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.
Clinical practice applications:
- 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.
Considerations for future research:
- Further research could determine exercise specific dosage recommendations.
Abstract
In recent years, an increasing trend has been observed in the consumption of specific polyphenols, such as flavonoids and phenolic acids, derived from green tea, berries, and other similar sources. These compounds are believed to alleviate oxidative stress and inflammation resulting from exercise, potentially enhancing athletic performance. This systematic review critically examines the role of polyphenol supplementation in improving aerobic endurance among athletes and individuals with regular exercise habits. The review involved a thorough search of major literature databases, including PubMed, Web of Science, SCOPUS, SPORTDiscus, and Embase, covering re-search up to the year 2023. Out of 491 initially identified articles, 11 met the strict inclusion criteria for this review. These studies specifically focused on the incorporation of polyphenols or polyphenol-containing complexes in their experimental design, assessing their impact on aerobic endurance. The methodology adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, and the risk of bias was evaluated using the Cochrane bias risk assessment tool. While this review suggests that polyphenol supplementation might enhance certain aspects of aerobic endurance and promote fat oxidation, it is important to interpret these findings with caution, considering the limited number of studies available. Systematic Review Registration: https://www.crd.york.ac.uk/PROSPERO/, identifier CRD42023453321.
Methodological quality
Jadad score
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Not applicable
Allocation concealment
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Not applicable