Green tea is one of the most widely consumed herbs in the world.
It has been used for thousands of years. Historically, green tea was used as a daily beverage and in Traditional Chinese Medicine (TCM) for treating various ailments.
Modern research has shown that green tea and its compounds may offer numerous health benefits, especially for metabolism, brain health, inflammation, heart health, and more.
This article will detail the health benefits of green tea, its major bioactive compounds, and how to incorporate it into one’s diet.
Table of Contents
- What is Green Tea?
- Health Benefits of Green Tea:
- Green Tea Safety:
- Naming & Taxonomy:
- History & Traditional Use:
What is Green Tea?
Green tea comes from the leaves of the tea tree, which is scientifically known as Camelia sinensis.
The tea plant is a small, evergreen shrub native to the mountainous regions of Japan and China.
Green tea is rich in many different bioactive compounds, such as:
- Flavonols, especially the catechins
- Phenolic acids
- Vitamins, including vitamin C, vitamin E, and beta-carotene
- Potassium and other minerals
Out of all of these compounds, the ones with the most researched health benefits are the catechins, a group of natural antioxidants.
There are four primary catechins that are found in green tea, they include:
- epigallocatechin-3 gallate (EGCG)
- epigallocatechin (EGC)
- epicatechin gallate (ECG)
- epicatechin (EC).
Among these, EGCG takes up nearly 60% of the total catechin content, and it also appears to be the most beneficial catechin in terms of health effects. It has been shown to benefit weight loss, antioxidant function, and more.
Health Benefits of Green Tea:
Green tea and its compounds, especially EGCG and other catechins, have received a lot of research attention in recent years. Many studies, including tremendous clinical evidence, show that green tea benefits the body in a number of different ways.
In particular, green tea is associated with the following health benefits:
1. May Support Weight Loss
A substantial amount of research shows that green tea benefits weight loss and metabolism.
In one clinical trial of 115 women with obesity, those who took a high-dose green tea extract lost significantly more weight compared to the placebo. Additionally, the green tea group had significantly lower levels of ghrelin, a hormone involved in feelings of hunger and metabolism, among other things.
In another clinical trial in 120 overweight adults, supplementing with a green tea meal replacement formula for 12 weeks helped with weight loss and body fat reduction compared to the placebo. Moreover, those who received the green tea formula had significantly lower cholesterol levels.
Also, a clinical study done on 70 women with metabolic syndrome showed that the women who were given green tea daily for eight weeks had significantly lower waist circumference, body mass index (BMI), and waist-to-hip ratio compared to the placebo. Those who consumed green tea also significantly improved systolic blood pressure, blood sugar, and LDL cholesterol.
Another clinical trial in 60 obese subjects found that those who supplemented with green tea for 12 weeks had significant weight loss compared to the control group. The researchers also noted that individuals who consumed green tea had significantly higher resting energy expenditure and fat oxidation. These factors increase calorie burning, which makes losing weight easier.
To be fair, not all studies have shown benefits, however. For example, one clinical trial involving 78 obese women found no significant difference in weight loss, BMI, and waist circumference in women who were supplemented with green tea extract or a placebo for 12 weeks.
Summary:Clinical human research has found that green tea supplementation may be beneficial for reducing body fat and aiding in weight loss.
2. May Support Blood Pressure and Heart Health
In a clinical trial involving 20 obese women with high blood pressure, those who were given 500mg of green tea extract for four weeks had significant reductions (2 to 5mmHg) in systolic blood pressure compared to the placebo group.
In another clinical trial in 58 obese, hypertensive individuals, supplementation with 379mg of green tea extract for three months was associated with significant reductions in systolic and diastolic blood pressure. Those who took green tea also had significantly improved cholesterol, triglyceride, inflammation, and antioxidant profiles.
In a 12-week clinical trial in 240 adults with obesity, those who were given a high-dose green tea extract (583mg of catechins) had significant reductions in systolic blood pressure, body fat, and LDL cholesterol compared to the placebo. Altogether, green tea extract supplementation appeared to reduce key cardiovascular risk factors.
Additionally, a clinical study in 111 healthy adults showed that supplementation with Camellia sinensis capsules was associated with significant reductions in numerous cardiovascular risk factors compared to placebo. For example, the treatment group had significantly lower blood pressure, cholesterol levels, and inflammation compared to the control group.
However, another clinical study in 51 healthy subjects found no significant difference in blood pressure, cholesterol, or other heart health risk factors after supplementing with either a low (100mg) or high (400mg) dose of green tea catechins. One possible explanation is that the participants were from Japan and, thus, may have already been consuming green tea regularly, which could make the effects less significant.
Summary:Human studies indicate that green tea may benefit heart health by lowering blood pressure and supporting heart health.
3. May Support Skin Protection
A number of studies also show the potential protective benefits of green tea on skin damage from the sun.
In one clinical study, volunteers were treated with an extract of green tea or one of its four catechins on patches of skin before being exposed to UV radiation. The researchers found that green tea extracts, especially EGCG and ECG, reduced skin redness and damage from UV radiation, essentially preventing sunburn.
Also, in an extensive two-year, double-blind clinical trial on 56 women, subjects who received 250mg of green tea polyphenols significantly improved sun damage, skin redness, and telangiectasias (small, widened blood vessels on the skin) on facial areas compared to the control group.
Another clinical trial on 44 healthy elderly individuals showed that skin treatment with green tea polyphenols for six months was associated with significant reductions in wrinkles and skin roughness. Additionally, the green tea polyphenol treatment was associated with significant increases in antioxidant activity.
In another clinical trial of 80 women with acne, those who were given 1,500mg of green tea extract (containing 856mg of EGCG) for four weeks showed significant reductions in acne around the nose, mouth, and chin compared to the control group.
Also, an in vivo study found that applying green tea polyphenols to human skin exposed to UVB radiation limited DNA damage and skin redness. The researchers concluded that green tea extract might be an effective strategy to reduce UV-induced skin cancer risk.
Summary:Clinical trials show that green tea may benefit the skin by reducing wrinkles, acne, roughness, and redness. Green tea may also lower UV/UVB radiation risk.
4. May Stabilize Blood Sugar Levels
A few clinical studies also show that green tea may support individuals with diabetes, particularly type 2 diabetes, by working to improve blood sugar levels.
In a clinical trial involving 100 patients with type 2 diabetes, taking a cup of green tea daily for four weeks was associated with significant improvements in insulin levels and insulin resistance compared to hibiscus tea consumption. This study is important since insulin is a powerful hormone that helps shuttle blood sugar into the body’s cells for energy.
In another clinical trial in 77 patients with type 2 diabetes, patients who were given 500mg of green tea extract three times per day for 16 weeks showed significant improvements in triglycerides and insulin resistance, as well as increased glucagon-like peptide 1 (GP1).
GP1 is a hormone that releases insulin and can help control blood sugar. However, these effects were within-group (meaning that there were significant benefits at the end compared to the beginning of the study in the same group). Moreover, the levels weren’t significant compared to the placebo.
Also, another clinical trial involving 20 individuals with type 2 diabetes found that supplementing with 400mg of green tea (standardized to contain 45% EGCG) for 12 weeks was associated with significant decreases in arterial stiffness compared to controls. This finding is important because type 2 diabetes is a risk factor for cardiovascular disease and can lead to arterial stiffening and atherosclerosis.
In a retrospective study of over 17,000 healthy Japanese individuals, researchers looked into the relationship between green tea consumption and diabetes risk over five years. They found that those who drank 6 or more cups of green tea daily were significantly less likely to have diabetes than those who drank one cup or less per day.
Lastly, a clinical study involving 80 overweight individuals with type 2 diabetes found that taking 1,500mg of green tea daily showed significant reductions in HbA1C (a marker of blood sugar). However, these reductions were seen in both the treatment group and the placebo group.
Summary:Clinical human studies indicate that green tea may help to stabilize blood sugar levels.
5. Anti-Cancer Properties
Green tea supplementation has also been shown in a few studies to have anti-cancer actions. It is one of only a few herbs with clinical studies in this domain.
In one clinical trial on patients with high-risk oral pre-cancerous lesions, those who supplemented with green tea extract for 12 weeks improved clinical markers of oral cancer risk, although they weren’t statistically significant.
In a pilot study in 136 patients with noncancerous colorectal tumors, those who were given a green tea extract (equivalent to over 10 cups of green tea) daily for 12 months showed significant reductions in the reappearance of colorectal tumors and overall colorectal cancer risk compared to the placebo.
In another clinical study on 60 men with pre-cancerous prostate tumors, those who were given 600mg of green tea catechins per day for 12 months showed significantly lower tumor rates than the placebo. Additionally, compared to the control group, the treatment group had significant improvements in prostate symptoms, such as frequent urination, and overall quality of life.
Also, in another clinical study done on 472 individuals with stage I, II, or III breast cancer, consumption of green tea was associated with a reduced likelihood of metastatic cancer (cancer that spreads from the original site). Moreover, increased consumption of green tea was associated with a reduced recurrence of stages I and II breast cancer in follow-up studies.
Lastly, an in vitro and in vivo combination study found that EGCG and other green tea catechins had synergistic effects with other anti-cancer compounds. They found that EGCG catechin administration alongside other anti-cancer compounds showed an average tumor reduction of over 70%.
Summary:Initial research shows that green tea may have benefits for indivduals with cancer. Additional research is needed.
6. May Improve Cognitive Function
The last benefit this article will go over is cognitive function. Like most other benefits, significant research, including clinical studies, show that green tea benefits cognitive function and may reduce cognitive decline.
In a prospective study on 490 individuals aged 60 and over, consumption of green tea was significantly associated with a reduced risk of mild cognitive impairment and dementia. In contrast, no such benefits were found for coffee or black tea consumption.
Also, in a clinical trial on 33 elderly individuals with cognitive dysfunction, those who were given 2g of green tea powder (220mg of catechins) for 12 months had significantly lower markers of oxidative stress. However, the changes in cognitive performance weren’t significant compared to the control group.
Another clinical trial in adults aged 50-69 found that those who supplemented with 336mg of green tea catechins for 12 weeks significantly improved memory recall.
In a clinical trial in 44 healthy individuals aged 36 to 64, it was found that those who took 500mg of a high-dose catechin green tea extract for eight weeks significantly improved cognitive functions, such as memory, attention, and executive function, compared to the placebo.
Finally, in a pilot study done on 12 elderly nursing home residents with cognitive dysfunction, taking 2g of green tea powder for three months was associated with significant improvements in cognitive function and mental performance, including attention and memory.
Summary:Clinical human trials have discovered that green tea may be useful for improving cognitive function, attention, memory, and mental performance.
Green Tea Safety:
As it is currently known, green tea appears safe when consumed in upwards of eight cups per day.
If pregnant or breastfeeding, one should limit their consumption of green tea to no more than six cups per day (300mg of caffeine). Drinking more than this may increase the risk of negative effects, such as neural tube defects.
Also, green tea has been associated in some cases with liver damage, although this is typically from higher-dose green tea extracts in pill form.
The possibility for liver damage and other effects stems primarily from EGCG-rich extracts. Research shows that it is generally safe to consume 338mg or less of EGCG in powder form or up to 704mg in regular beverage form.
Always talk with your doctor or healthcare practitioner before taking any supplement.
As of yet, there is no optimal dose determined for health benefits. However, based on clinical research, a dosage of anywhere from one to eight cups of green tea per day is likely to yield health benefits. Green tea seems to be especially helpful when consuming over three cups per day.
Many benefits of green tea supplementation are related to catechin content, especially EGCG. When buying a green tea extract supplement, look for a green tea extract formula that is standardized to roughly 50% EGCG.
Most research shows health benefits with an EGCG dosage of around 300 to 800mg (keep in mind the safety concerns of higher doses).
Naming & Taxonomy:
Green tea (Camellia sinensis) is part of the Theaceae family.
The other types of tea are black tea and oolong tea. Unlike these forms, green tea is made from leaves that have not gone through a withering and oxidation process.
It is a small, evergreen shrub with white flowers. It can grow to 30 feet, but it is usually pruned to remain at two to three feet.
One may identify the green tea plant by its dark green, ovalish leaves with serrated edges and a pointed tip. The undersides of green tea leaves are often hairy and typically grow between five and 10cm in length.
Also, the green tea plant has white, fragrant flowers, each with seven to eight white or pink-tinged petals with yellow stamens. Green tea is known for its grassy, fresh scent.
History & Traditional Use:
The use of green tea leaves likely dates as far back as 3,000 years in southwest China and the surrounding areas.
It is often said that the Chinese emperor Shennong drank the first cup of green tea.
It has been used for thousands of years in China, Japan, India, and other areas, primarily as a beverage rather than for specific medicinal purposes.
However, green tea was used in some cases for medicinal purposes, including its use as a stimulant, astringent, and headache reliever.
Green tea is the second most popular beverage globally and has many possible medicinal benefits.
Research has shown that green tea has many beneficial compounds, especially EGCG and other catechins. Moreover, many clinical studies have shown that green tea may benefit weight loss, heart health, skin, diabetes, cancer, and cognitive function.
Lastly, green tea can be easily incorporated into the diet, whether through the consumption of a traditional beverage or a more potent extract, for possible health benefits.