Polyphenols and Performance: Natural Supplements That Can Boost Endurance
Summary: For those on the move
The article discusses how polyphenols, natural compounds in plants, can affect training and recovery. Research shows that polyphenol supplements – for example, from berries, green tea, and grapes – can enhance aerobic endurance, increase fat oxidation, and reduce oxidative stress. The results suggest that regular intake can offer small but measurable performance improvements, especially during longer training periods. At the same time, it is emphasized that the exact dosage and the balance between benefits and excessive antioxidant effects have yet to be fully determined.
What are polyphenols and why are they important?
Polyphenols — it sounds like something from the plastics industry, but it’s quite the opposite. Polyphenols are natural substances found in plants and act as their own defense. They help plants withstand frost, pests, rot, sun, or simply make them taste so bad that nothing eats them (hello nettles). Some of these substances are actually toxins to keep hungry pests away — nicotine and caffeine are well-known examples from the tobacco and coffee plant.
Polyphenols also give berries and fruits their color, taste, and aroma. They are divided into several subgroups — flavonoids, anthocyanins, quercetin, and tannins (the stuff that makes grapes astringent) — but we won’t get tangled in chemistry trees here. What's important is that you're already consuming polyphenols daily through your diet: a cup of coffee or tea, a glass of wine, fruits, and berries.
Polyphenols, ROS, and the balancing act of training
We know that other phytochemicals like caffeine and nicotine have well-documented performance-enhancing effects in the right doses. But where do polyphenols fit on that scale? We have previously highlighted this area more specifically through studies on blackcurrant powder and cherries, while this article is broader and looks at polyphenols as a group.
Research on polyphenols is developing rapidly, and previous perceptions may need adjusting. Polyphenols are not the same as antioxidants, but they affect the management of ROS (Reactive Oxygen Species), essentially the "oxygen damage" that arises when we train. During an intense session, mitochondria need to handle up to 200 times more oxygen than at rest, so they are extremely adaptable — but even they have their limits. ROS) also function as signaling molecules for muscles and vessels, instructing the body to adapt (stronger muscles, more capillaries, etc.). Too much ROS leads to oxidative stress and cell damage, too little ROS prevents adaptations — hormesis in a nutshell. The same principle applies to training: moderation is best.
If you feel recovery is lagging despite sleep and nutrition, polyphenols may be a tool to shift you from "subpar" to "moderate" recovery, thus gaining more from training #fasterbetterstronger.
Okay, that was a long intro — now let’s dive into the studies 🙂
About the Study: Polyphenol Supplements and Endurance in Athletes
The article titled “Polyphenol supplementation boosts aerobic endurance in athletes: systematic review” examines the effects of polyphenol supplements on aerobic endurance in athletes and active individuals.
Polyphenols occur naturally in plants like green tea, berries, and grapes and are known for their antioxidant and anti-inflammatory effects. This study explores whether supplements can enhance endurance and mitigate the negative impacts of intense training – such as oxidative stress and inflammation– which influence muscle function and recovery.
Researchers' Approach
The review is based on 491 initially identified articles, of which 11 met the inclusion criteria. A total of 221 people participated, 56 of whom were elite athletes. Only 5 women were included. The age range was 18–48 years.
Among the 11 studies, various polyphenol sources were used:
- Grape extract
- Blackcurrants
- Decaf green tea
- Carob powder
- Citrus extract
- Haskap berries
- Cherry powder
- Whole berries: intake often around 6 g/day over 6–7 days
- Extracts/powders: intake 300–571 mg/day, with setups ranging from an acute dose before/after sessions to continuous intake over 1–6 weeks.
- Polyphenol-rich shots (2 studies): 6–8 ml/day over 1–2 weeks.
Put this in perspective: in a Western diet, we consume about 900 mg of polyphenols per 1,000 kcal, which for an active person amounts to around 2–3 g of polyphenols/day, mainly from tea/coffee and fruit. So we already get quite a lot — the question is whether more is beneficial and performance-enhancing?
Results: Increased Endurance and Improved Recovery
The studies varied in design but jointly focused on endurance and performance. Common polyphenols were flavonoids and anthocyanins. The review results showed that polyphenol supplementation generally improved certain endurance parameters, including:
- Increased time to exhaustion
- Improved competition speed (shorter race completion time)
- Increased fat oxidation compared to the control group
For instance, in a study with 14 males who received either a placebo or green tea extract for 4 weeks, fat oxidation increased by 25% in the extract group (from 0.24 g/min to 0.30 g/min), while the placebo group showed no change. The effect in absolute terms was small, but over longer distances where glycogen runs low, increased fat oxidation can be valuable.
Overall, the majority of studies showed positive effects on performance, including increased lactate threshold and delayed exhaustion. Similar doses have been noted in previous reviews (500–1,000 mg/day) and a commonly studied polyphenol is quercetin, which is already present in many dietary supplements.
Mechanisms Behind the Effects
The proposed mechanisms include:
- Increased production of nitric oxide (NO) which dilates blood vessels and improves blood flow to working muscles, potentially enhancing oxygen delivery.
- Reduced production of reactive oxygen species (ROS) through antioxidant effects.
- Activation of the body's own antioxidant systems, particularly via the Nrf2 signaling pathway, linked to mitochondrial biogenesis and training adaptation.
In tests, performance increases often range around 2–5 percent with daily intake, preferably for at least six weeks. Acute intake or very short intervention periods (1–2 weeks) often appear too brief to provide clear performance gains — the trend suggests that longer intake yields greater effects.
Summary: Small Effect — but Clear Trend
The review suggests that polyphenol supplements may have a beneficial effect on aerobic endurance, primarily through improved blood flow, oxygen transport, and reduced oxidative stress. The results support the idea that polyphenols can act as natural performance enhancers, but more research is needed to determine optimal dosing and which specific polyphenols are most effective for different training forms.
Nonetheless, we emphasize that the “perfect” level of ROS has not yet been established. Even if an optimal level is found in a study group, it may be challenging to generalize it to all athletes and active individuals.