Green tea has been a component of the diet since ancient times. Because of its popularity and nutrient-dense profile, this delicious beverage is also well-researched. From metabolism to mood to longevity, green tea proves to have multiple powerful effects on the body. Lately, green tea extract supplements, a potent form of green tea, have become popular for their beneficial, antioxidant impact on exercise recovery. But does research support using this potent pill for training gains? We take a deep dive into the scientific literature here. 

What properties does green tea extract contain that make it so desirable?

Green tea extract, also known as Camellia Sinensis, is a concentrated form of the beneficial compounds found in green tea leaves. The impact of drinking green tea on health and longevity is well established—drinking green tea daily is associated with a 5% reduction in all-cause mortality and a reduction in the risk of age-related cognitive decline. [1] But what is responsible for the life-sustaining properties of green tea? Green tea is antioxidant-rich and specifically contains the catechin epigallocatechin-3-gallate (EGCG). EGCG can reduce cellular damage and plays a fundamental role in glucose and lipid metabolism. Scientists speculate that EGCG’s antioxidant properties contribute to longevity because glucose and lipid metabolism are critical indicators of aging. [1] 

Understanding the connection between strenuous exercise and oxidative stress

These antioxidant properties in green tea may be also relevant for exercise. Oxidative stress, a type of cellular damage, is caused by several factors, including high-intensity exercise—strenuous exercise increases the generation of reactive oxygen species (ROS) by cells, particularly by activation of the xanthine oxidase (XO) pathway, which increase oxidative stress and cellular damage.[2] [3] However, the cellular damage caused by ROS during exercise is critical for training adaptations—this damage is what enables muscles to get stronger over time. 

Oxidative stress during exercise also causes creatine kinase (CK), an enzymatic protein found in muscle cells that aids in energy production during the onset of exercise, to leak into the bloodstream. When muscle cells get damaged from oxidative stress during exercise, CK escapes the cell and can end up traveling around the body. Therefore, after a challenging workout, a high blood CK level is expected. However, chronically elevated blood CK levels indicate overtraining and trigger the body into a protective mode to preserve muscle tissue and reduce the risk of injury. High levels of CK can also leave you feeling fatigued and sore. [4] 

The role (and paradox) of antioxidant supplements like green tea extract in post-workout recovery

Oxidative stress and blood CK levels have complicated relationships with exercise and training adaptations. On the one hand, an over-presence of either can indicate overtraining and can result in harmful damage to the cells and tissues in the body. But on the other hand, their absence can prevent an athlete from making meaningful progressions in their training.

Exercise scientists hypothesize that antioxidant-rich foods and supplements that decrease CK post-exercise can improve recovery after a strenuous workout via their impact on oxidative stress reduction. But while antioxidant-rich foods and beverages can diminish exercise-induced oxidative stress in the short term, scientists debate whether or not this interferes with long-term training adaptations.[2] [5]

This need for balance is of special interest to researchers, and the antioxidant properties in green tea extract have sparked enthusiasm from exercise physiologists for its potential recovery benefits. [3] For this reason, studies have looked at whether green tea extract can combat exercise-induced oxidative stress and whether it could impact athletic performance. Here are some key findings.

A summary of the research on green tea extract on athletic performance

A trial of 14 men following a weight training program found that drinking green tea three times per day was associated with an attenuated rise in plasma CK and XO levels post-exercise after just one week. Participants in the green tea group also had higher total polyphenol and glutathione levels (two key antioxidants) than the control group. This data shows that drinking green tea may offer a protective effect against exercise-induced oxidative stress. [5]

A separate supplement study in 16 male athletes found that supplementing with 500 mg/day of green tea extract resulted in significantly lower fatigue and oxidative stress levels post cycling than a control group. Cyclists in the green tea extract supplement group also displayed improved measures of neuromuscular function compared to the control group, likely a result of reduced fatigue levels. [6]

Another study in 40 untrained males investigated the impact of green tea extract supplements on CK levels and endurance capacity. Researchers found that the 250 mg/day supplement attenuated the rise in CK and malondialdehyde (MDA, a marker of oxidative stress) levels post-exercise and increased total antioxidant status by 11%. Participants in the green tea extract supplement group had a 17% increased maximal oxygen uptake compared to control, showing that this supplement may actually improve endurance capacity. [7]

Finally, another study investigated the impact of a 980 mg/day green tea extract supplement on exercise performance in male sprinters. Sprinters taking a green tea extract supplement had increased total antioxidant capacity, and decreased MDA levels compared to the control group. But interestingly, the supplementation group did not produce significant improvements in sprint performance. [2]

As a whole, current research seems to indicate that green tea extract supplements can improve molecular markers of antioxidant status and muscle recovery without impairing performance outcomes. Further research is warranted to measure the impact of green tea supplements in females.

When is the best time to take a green tea extract supplement?

Taking a 500mg green tea extract supplement can benefit exercise performance when taken just prior to or between athletic events. Of note, this recommendation is similar to that for vitamins C and E, other common antioxidant supplements—they should only be taken in the short-term before athletic events. InsideTracker dietitians also recommend taking a green tea extract supplement with food to optimize its beneficial effects.

InsideTracker does not recommend taking green tea extract supplements for an extended period of time, though, as the potent antioxidant effect may reduce the body’s adaptive response to training and, at high doses, they can lead to stomach upset and potential liver damage. 

Summary of key points

• Green tea is antioxidant-rich and specifically contains the catechin epigallocatechin-3-gallate (EGCG), known for its impact on healthy aging. 
• Exercise induces oxidative stress, but there is debate around whether or not antioxidants, known to improve oxidative stress, impair training adaptations.
• Prolonged high levels of creatine kinase (CK) can impair recovery from workouts. 
• Green tea extract supplements reduce high levels of CK  and improve antioxidant status post-exercise compared to control exercise groups. 
• Green tea extract supplements should only be taken short-term, immediately before athletic events, with food.
• InsideTracker does not advise long-term antioxidant supplementation based on its impact on training adaptation.

Michelle Darian, MS, MPH, RD

References

[1] https://pubmed.ncbi.nlm.nih.gov/31544736/ 

[2] https://pubmed.ncbi.nlm.nih.gov/25120110/ 

[3] https://pubmed.ncbi.nlm.nih.gov/28819546/ 

[4] https://pubmed.ncbi.nlm.nih.gov/17569697/ 

[5] https://pubmed.ncbi.nlm.nih.gov/18337059/ 

[6] https://pubmed.ncbi.nlm.nih.gov/30174618/ 

[7] https://pubmed.ncbi.nlm.nih.gov/26319566/