Green Tea Extract: 5 Evidence-Based Health Benefits

The magical benefits of green tea extract have long been used in ancient cultures. As per Healthline, the most popular advantages of this tea include:

• High in antioxidants;
• May promote heart health;
• Good for the brain;
• Can help with weight loss;
• Might benefit liver function;
• May reduce the risk of cancer;
• Its components may be good for the skin;
• May benefit exercise performance and recovery;
• May help lower blood sugar;
• Easy to add to your diet.

Thumbs up if you noticed that every second benefit contains “may/might” modal verbs. So, the author is not confident whether these points are real.

Therefore, we decided to gather all the information given from the latest researches to dot the “I’s” and cross the “T’s.”

Let’s see what the true evidence-based benefits of green tea extract are.

Green Tea to Fight Fatigue

Muscle fatigue is considered a limiting factor in athletic performance. Its origins are multifactorial, but fatigue has been accepted to include ATP depletion, muscle damage, and increased production of reactive oxygen species (ROS), leading to a state of oxidative stress.

In general, fatigue negatively affects force production. In the case of cycling, pedal force, power output, and cadence are impaired. Repeated sessions of strenuous physical activity lead to a state of cumulative fatigue, in which the ability to develop effort is reduced. For the quadriceps muscles, recovery from fatigue can take up to 3 days.

In addition to the acute (one-time) effect of fatigue on performance, successive fatigue exercise sessions can lead to poor performance during training and competition.

Cumulative fatigue conditions can also increase the risk of injury and contribute to negative psychobiological adaptations. However, there are many situations in which athletes have no choice but to maintain their performance when tired.

Therefore, strategies to minimize fatigue’s effect on performance during repeated sessions of physical activity are of interest to both coaches and athletes. A realistic strategy for achieving this goal is to promote faster recovery from exercise.

Why Use Green Tea Extract

In this regard, supplementation with natural products has attracted the interest of athletes of various competitive levels.

Given that oxidative stress and muscle damage are important in fatigue and its effect on performance during repetitive exercise sessions, there is a lot of interest in antioxidant supplements such as green tea extract (GTE) from Camellia sinensis.

Green tea extract is rich in polyphenols, including epigallocatechin gallate, epicatechin, epigallocatechin, and epicatechin gallate, which lead to potent antioxidant (antioxidant) activity.

Previous research has shown that GTE supplementation can reduce oxidative stress and help to improve maximum oxygen uptake while cycling to exhaustion.

In addition, GTE may reduce muscle soreness resulting from eccentric exercise and reduce markers of muscle damage after eccentric training, intense aerobic exercise, and strength training.

However, no similar effects were found when a single dose of GTE was taken prior to intense muscle-endurance tests.

Research on the Effect of Green Tea Extract on Muscle Damage

The effects listed for regularly taken green tea extract supplements on muscle damage and oxidative stress suggest that GTE may be an effective strategy to maintain performance during repetitive bouts of exercise leading to cumulative fatigue.

To address this issue, a study (triple-blind, placebo-controlled experiment) described below was conducted, the main goal of which was to determine whether the addition of green tea extract (GTE) from Camellia sinensis minimizes muscle damage and oxidative stress in trained athletes undergoing sequential exercise sessions leading to cumulative fatigue, whether it will contribute to the preservation of neuromuscular function.

Sixteen trained male recreational athletes were randomly assigned to either the GTE group supplemented (500 mg extract/day – one capsule daily, before breakfast with a glass of water) or placebo consumed for 15 days.

The effects of the supplement were tested in repeated trials of submaximal cycling on a bicycle ergometer at 60% peak power output, performed following a protocol of cumulative hip extensor muscle fatigue.

Cumulative fatigue was here defined as the state of the subject after completing knee extension workouts to complete exhaustion for two consecutive days before the submaximal cyclic test.

Green Tea Extract Reduced Muscle Damage

Muscle damage and oxidative stress showed lower values ​​in response to fatigue after GTE supplementation.

The placebo group showed impaired neuromuscular activity and higher muscle damage (plasma CK) and oxidative stress (byproducts of lipid peroxidation – TBARS) compared with the GTE group during the cycling test for cumulative fatigue.

Cardiovascular responses assessed by heart rate showed that the GTE group had a lower heart load (HR) than the placebo group.

Green Tea Supports Neuromuscular Communication

Neuromuscular activation from the left vastus lateralis (LVL) of the placebo group showed significant worsening of fatigue. Fatigue had an impact on the magnitude of neuromuscular activity, assessed by the rms values, which showed a decrease in neuromuscular activation by the end of the exercise in fatigue in the placebo group but not in the GTE group.

Thus, GTE’s addition has been shown to have a positive effect on neuromuscular function in response to the state of cumulative fatigue. It suggests that the addition of GTE can serve as a strategy to improve and maintain performance in the face of cumulative fatigue.

Findings

“Supplementing green tea extract prior to a cumulative fatigue event will minimize muscle damage and oxidative stress in trained athletes. 

Green tea extract also has a positive effect on neuromuscular parameters associated with muscle activation and muscle fatigue. 

Therefore, supplementation can be seen as the right strategy in the context of competitive endurance sports, when the goal is to prevent a decline in performance,” the researchers concluded.

Green Tea vs Cortisol

Green tea is a cortisol inhibitor and can be very effective. Pharmacologists at the University School of Medicine Schleswig-Holstein in Germany discovered this when they conducted an in vitro study. Unfortunately, it is too early to tell what the dosage should be.

11-Beta-HSD-1 (11β-hydroxysteroid Dehydrogenase Type 1)

There are several enzymes in the human body that regulate the metabolism of cortisol. The enzyme 11-Beta-HSD-1 converts the inactive hormone cortisone into the stress hormone cortisol. And an enzyme, 11-Beta-HSD-2, converts cortisol back to inactive cortisone.

In studies on laboratory animals, it has been found that when the activity of 11-Beta-HSD-1 is reduced, animals lose visceral fat. Their cells become more sensitive to insulin, their cholesterol levels rise, and their blood pressure drops.

The 11-Beta blockers of HSD-1 may be of interest for the manufacture of drugs for the treatment of type 2 diabetes.

Which Tea Is Healthier: Green, Black, or White

The tea plant occurs naturally in southern China but is currently cultivated in many other regions of the world’s major tea producing countries such as India, Japan, Sri Lanka, Indonesia, and Kenya.

In general, tea can be divided into three types (percentage of world tea production):

1. unfermented green tea (20%), 
2. semi-fermented tea (such as oolong and white tea) (2%),
3. fermented black tea (78%). 

In addition, there are over 300 different types of tea that differ with respect to the production process.

The most popular type of tea consumed in the world is black tea, while green tea is mainly consumed in China and Japan.

Recently, there have been many commercial drinks on the market that contain tea extracts or catechins from tea.

Today, the daily consumption of tea or drinks containing tea extracts is considered a lifestyle that can support health and long life, as evidenced by a number of laboratory, epidemiological studies, and interventional studies in humans [11] – [15].

In particular, green tea consumption has been associated with a reduced risk of cardiovascular disease, some forms of cancer, and in promoting oral hygiene and other physiological functions such as antibacterial and antiviral activity, neuroprotective properties, hypotensive effects, body weight control, and prevention. type 2 diabetes [16], [17].

The latter diseases are risk factors for metabolic syndrome (obesity, insulin resistance, arterial hypertension, type 2 diabetes mellitus, dyslipidemia), against which the therapeutic potential of tea has been demonstrated in humans and model organisms in numerous studies [18] – [22].

In traditional Chinese medicine, tea has long been used to treat type 2 diabetes. Could tea be an 11-Beta-HSD-1 inhibitor?

Scientists to Answer The Question

To try and answer this question, German researchers exposed liver cells to green, black, and white tea extracts, added cortisone to the liver cells, and then measured how much cortisol was produced.

All three teas significantly suppressed cortisol production, but green tea worked best.

Green tea contains a lot of biologically active substances.

Researchers exposed liver cells to the most important of them and then measured how well they inhibit the conversion of cortisone to cortisol. Two substances, epigallocatechin gallate [EGCG] and gallocatechin [GC] were found to be cortisol inhibitors. Moreover, the first was more effective.

The researchers used spatial models of 11-beta-HSD-1 to figure out how EGCG deactivates the enzyme.

EGCG was found to bind to the active site of the 11-beta-HSD-1 enzyme, which targets cortisone. As a result, the conversion of cortisone to cortisol cannot occur.

Effectiveness of Green Tea for Stress

“We conclude with evidence that aqueous extracts of tea (Camellia sinensis) are able to inhibit the production of cortisol by the 11β-HSD1 enzyme. Of the several abundant components of tea, the main phenolic compound EGCG can be identified as the most potent inhibitor of human 11β-HSD1 with inhibition constants Ki = 22.68 μm in microsomes and Ki = 18.74 μm for the purified enzyme, respectively. 

The mechanism of inhibition of EGCG is most likely direct binding to the active site 11β-HSD1, as supported by kinetic studies of enzymes and a computerized model of docking. Our results decipher the mechanism by which catechins such as EGCG or green tea, in general, have been successfully consumed for thousands of years for overall health benefits. 

These polyphenolic compounds may serve as model structures for the development of new drugs for the treatment of metabolic syndrome and related diseases.” the researchers conclude. [23]

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