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Science Behind Why Japanese Green Tea is Good for Health

Leaves have been a staple for both internal and topical medicine. In early centuries, leaves are the best tool to treat wounds, and even ingested for other internal sickness. Among leaves that are beneficial for health, green tea has been one of the favorites.

Green tea has been a favorite among the Japanese for centuries. It is said that in 805 Buddhist monks Kukai and Saicho returned to Japan with young tea trees after studying in China. In 1181, another Buddhist monk named Eisai had been studying in China. Eisai introduced and popularized the sipping of tea for optimum health. About the same time, farmers started growing green tea in Uji, Kyoto. The last health reference Japanese book of Eisai’s about tea was in 1211; Kissa Yojoki (the Book of Tea).

With the introduction of green tea to Japan, along came much of the knowledge of it many health benefits. And through the extended use, advanced cultivation and learning of its many discovered medicinal values, Japanese green tea has remained a greatly valued beverage and food. Considered as one of the cure-all beverages, many products that market health benefits would never go wrong with incorporating green tea in their items.

drinking japanese green tea

Great Health Benefits

Rendering to WebMD, green tea is a widely studied tea that has high concentrations of epigallocatechin gallate (EGCG). Considering that green tea is mostly unprocessed from unoxidized leaves, the higher amount of antioxidants in green tea compared to other tea leaves help combat cancer growth in the stomach, lungs, pancreas, breast and bladder. As well, the high antioxidant contents found in green tea may prevent the arteries from clogging. What is more, many studies find that this amazing tea may be able to burn fat, lower the risk of neurological disorders like Parkinson’s and Alzheimer’s, offset oxidative stress on the brain, improve cholesterol levels and lower the risk of stroke.

In addition to its powerful antioxidant effects, green tea has been shown to promote heart health by improving blood vessel function and lowering blood pressure. This is largely attributed to the polyphenols and catechins found in green tea, which have a protective effect on blood vessels and help reduce inflammation. Regular consumption of green tea has also been linked to a lower risk of developing cardiovascular diseases, making it a vital beverage for maintaining overall heart health.

Moreover, green tea is known for its metabolic-boosting properties, which contribute to weight loss and fat burning. Studies suggest that the combination of catechins and caffeine in green tea can enhance fat oxidation, particularly in the abdominal area. As a result, incorporating green tea into a healthy diet and exercise routine may help support weight management efforts. Additionally, green tea may help improve insulin sensitivity, making it a beneficial drink for those looking to manage blood sugar levels and reduce the risk of type 2 diabetes.

A Rich Antioxidant

Green tea is renowned for being rich in antioxidants, particularly epigallocatechin gallate (EGCG). In fact, many claim that this special antioxidant is what makes green tea have such powerful medicinal properties. Moreover, a recent post from Livestrong states that the epigallocatechin gallate in green tea may help lower total body weight and body fat levels. In fact, the fat burning antioxidant helps increases your body’s metabolism, especially visceral fat or fat that is in the abdomen. (Read more about green tea and diet effect in my other article)

According to Livestrong, epigallocatechin gallate may also be beneficial for people at risk of developing type 2 diabetes, who are overweight and have high blood pressure. This is because this special antioxidant may increase fat burning abilities or boost the transport of stored fat to cells for oxidation. (Read more about green tea and diabetes in my other article)

However, research suggests that epigallocatechin gallate may not promote fat loss but with a larger dose taken with caffeine, it may create increased fat loss. Also, some studies show that patients with glucose problems had a decrease in circulating glucose levels which often goes with weight issues. (Read more about this topic on my another article - Japanese Green Tea and Diet)

ECGG also, being an antioxidant ingredient, prevents and fights hair loss. Due to green tea’s anti-inflammatory nature, it also helps to reduce dandruff by simply putting green tea leaves or extract on the scalp and massage it.

Moreover, beyond its internal benefits, the antioxidants in green tea also promote overall skin health. Regular use of green tea extract in skincare routines has shown promise in reducing signs of aging, protecting against sun damage, and preventing acne. Its potent antioxidant properties fight off free radicals that contribute to skin aging, and its anti-inflammatory effects reduce redness and irritation, providing a clearer, healthier complexion.

L-theanine

Another beneficial substance found in green tea is L-theanine or theanine. This amazing amino acid is found naturally in green tea. It is said to support many health issues such as anxiety, insomnia, stress, depression, high cholesterol and high blood pressure.

In addition, theanine is claimed to support weight loss, increase concentration and improve the immune system. As well, some specialists believe that theanine may prevent Alzheimer's, stroke and some types of cancer. (Read more about this topic on my another article - Cancer and Japanese Green Tea - Why It is Good for Treatment and Prevention)

Japanese green tea in a mug

Specifically, in a 2018 study made regarding the effects of green tea’s ECGG on cancer, it was found out that those who continuously consume green tea for 10 years could delay the growth of cancer by 7.3 years compared to those who have not consumed green tea.

What is more, theanine also shows promise as an aide for weight loss especially when combined with certain caffeine’s. In fact, theanine is often used as a supplement to shed pounds.

In addition to its effects on weight loss and cancer prevention, L-theanine is also known for its calming effects on the mind. It is believed to promote relaxation without causing drowsiness, which makes it an ideal solution for those struggling with anxiety or sleep-related issues. By increasing alpha brain wave activity, theanine helps induce a state of relaxed alertness, which can improve focus and cognitive performance, making it a favorite among students and professionals alike.

Furthermore, L-theanine works synergistically with caffeine in green tea to improve cognitive function. Unlike coffee, which can cause jitteriness and a crash in energy, the combination of theanine and caffeine provides a more balanced boost in mental clarity and focus. This makes green tea an excellent option for enhancing productivity while reducing the typical side effects of caffeine consumption.

Polyphenols

Polyphenols that are found in tea include tannins, theaflavins, catechins and flavonoids. And in green tea there are epigallocatechin, epicatechin gallates, epigallocatechin gallates and epicatechins. As well, green tea contains flavanols like myricetin, kaempferol and quercetin. 

The polyphenols in green tea are said to have many health benefits like detoxing many vital organs and also preventing cancer. In fact, according to the National Cancer Institute, tea polyphenols have been shown to impede tumor cell proliferation and prompt apoptosis in laboratory and animal studies. As well, tea catechins have shown to obstruct tumor cell invasiveness and angiogenesis. (Read more about polyphenols in my other article)brewing Japanese tea

Polyphenols are also known to be a great anti-redness and anti-inflammatory content in green tea leaves. That is why green tea is also a popular content for facemasks to reduce redness and wellness, even rosacea and psoriasis. Green tea leaves are even used topically for sunburns and wounds to reduce redness and wellness. 

This same green tea content could also controls sebum secretion in the skin, which causes acne for majority of those who have oily skin. Polyphenols also fight against bacterial membranes that cause acne as well.

In addition to these impressive skin benefits, polyphenols are also shown to have protective effects on the liver. Studies have found that the antioxidants in green tea help reduce liver damage caused by inflammation, alcohol consumption, or a poor diet. Regular consumption of green tea may support liver function, detoxify harmful substances, and lower the risk of liver diseases like fatty liver disease or cirrhosis.

Additionally, polyphenols may improve gut health by acting as prebiotics, promoting the growth of beneficial gut bacteria. A healthy gut microbiome is essential for overall well-being, as it influences digestion, immune function, and even mental health. Research suggests that the polyphenols in green tea may help maintain a balanced gut microbiota, thus supporting digestion and overall gastrointestinal health.

Caffeines

Compared to other teas, green tea has about the lowest amount of caffeines (excluding non-caffeinated herbals teas). The highest is black teas and then white. However, caffeine content is also dependent on many variables like the brewing, type of buds and leaves and how the plant was grown. For example, how your tea is grown and packaged with affect the caffeines content. Teas grown is full sun have less amounts of caffeines than tea that is grown in the shade. Also, teas that are ground into powder, sliced or chopped will have a stronger dose of caffeines than the regular leaves. Additionally, the buds and leaves that are oftentimes used to make white tea have more caffeines than mature and older leaves.

While green tea contains less caffeine than black or white tea, it still provides a gentle and sustained energy boost, making it an ideal choice for people who are sensitive to the stronger effects of caffeine. The moderate caffeine levels in green tea help improve alertness and concentration, without causing the jitteriness or energy crash associated with stronger caffeinated beverages like coffee. This makes green tea a popular choice for those seeking a more balanced, prolonged boost of energy throughout the day.

Furthermore, the caffeine in green tea works synergistically with other compounds like L-theanine, which helps mitigate the stimulant effects of caffeine. This combination promotes a state of relaxed focus, which can improve mental clarity and productivity. Studies have shown that this unique pairing of caffeine and L-theanine in green tea enhances cognitive performance, making it especially beneficial for tasks that require sustained attention and concentration, such as studying or working on complex projects.

Fluorides

As of late, a concern with some consumers is the fluoride in both green and black tea. Further, green tea has two times more fluorides than black tea. On the other hand, many experts agree that the fluoride found in tea is at such minuscule levels that it would be difficult to consume enough tea to be toxic. In addition, about 50 percent of any type of fluorides is excreted and the other portion is deposited in the teeth and bones. (Read more about this topic on my another article - Science Behind Why Japanese Green Tea is Good for Health)

 Japanese green tea daily

In fact, Dr. Weil M.D. feels that the worries in regards to fluorides in tea are overstated. Although large amounts of the material can cause brittle bones after several years, but this is very rare. As well, fluorides are toxic in very high amounts which may cause gastrointestinal symptoms and sometimes death. For example, a large amount would be about 20,000 times more fluorides than what is found in an 8 ounce glass of water.

Moreover, the fluoride found in tea, including green tea, is naturally occurring and typically occurs at levels that are considered safe for consumption. According to the National Institutes of Health (NIH), the average daily intake of fluoride from drinking tea is generally within safe limits. However, for individuals concerned about fluoride exposure, it is always a good idea to monitor tea consumption and choose low-fluoride tea options. Additionally, most experts agree that the health benefits of drinking green tea far outweigh any potential risks associated with its fluoride content.

Interestingly, some studies suggest that fluoride in tea can even have positive dental benefits. In moderate amounts, fluoride can strengthen tooth enamel and help prevent cavities. This is one of the reasons why tea, especially green tea, is often considered beneficial for oral health. The fluoride content in tea, combined with its antibacterial properties, may help reduce the growth of harmful bacteria in the mouth, contributing to better overall dental hygiene.

Skin Benefits

It is known worldwide that green tea has so much benefits by simply drinking it, from brain function to weight loss. However, even after consuming a cup of green tea, its benefits do not end in drinking it since the left over tea leaves are often used to be face mask to get rid of acne. The ECGG and ECG contained in green tea even fights another type of cancer, which is skin cancer. This is due to the antioxidant properties contained in green tea leaves, which get rid of free radicals that harm the body, including the skin.

Japanese green tea for skin

ECG also fight ultraviolet rays from the sun that is a major factor in having skin cancer, as it enhances and repairs damaged DNA. The same green tea content also fights skin aging. ECG rejuvenates skin cells that prevent skin aging and dulling. Green tea also contains vitamin B2, which is also vital to have a healthier skin as it produces collagen in the body. Vitamin E is also found in green tea leaves that also fights skin aging and giving every person a healthier and more hydrated skin. Topically used, it produces more moisturizer in the skin and prevents skin roughness.  

Additionally, the polyphenols in green tea help reduce inflammation, which can prevent or treat conditions like eczema, psoriasis, and rosacea. These conditions often cause redness and irritation, but the anti-inflammatory effects of green tea can soothe the skin, reducing swelling and redness. Applying green tea topically may also help with conditions like sunburn and minor burns, as its antioxidant properties speed up the healing process and reduce the pain associated with these injuries.

Furthermore, green tea's high antioxidant levels help combat oxidative stress, which accelerates skin aging and the formation of wrinkles. By neutralizing free radicals, green tea helps protect the skin from environmental damage caused by pollution, smoking, and stress. With regular use, green tea can promote a youthful complexion, reducing the appearance of fine lines and wrinkles while maintaining a vibrant skin tone.

Conclusion

It is no doubt that historically Green Tea has been providing variety of health benefit and is believed to be one of the main reasons why Japanese people live longer and healthier compared to other part of the world. More recent study and researches reveals and confirms the benefit from different angles of science. We can enjoy all the benefit by simply having a good quality cup of Green Tea today and every day.

Green tea also offers a calming and enjoyable experience, making it an ideal beverage for relaxation and mindfulness. Whether you're sipping it in the morning to kick-start your day or enjoying it in the evening to unwind, green tea is not just a healthy drink—it's a lifestyle choice that promotes overall well-being. With its rich history, numerous health benefits, and versatility, green tea remains one of the best beverages you can incorporate into your daily routine.

This article was first published in 2016 and it was updated in 2022 just for you.

FAQs about the Science Behind Green Tea Health Benefits

What's the single most-studied health benefit of green tea — what's the strongest evidence?

Cardiovascular health, by a clear margin. The Ohsaki Study (Japan, 40,000+ participants, 11 years) found that drinking 5+ cups of green tea daily was associated with a 16% lower risk of cardiovascular death. The proposed mechanism is multi-factor: catechins improve endothelial function, lower LDL cholesterol, reduce blood pressure mildly, and improve insulin sensitivity — all of which compound over years.

Cancer prevention is the second-most-studied area but the evidence is more mixed. Some studies show modest reductions in specific cancers (stomach, lung, prostate), others show no effect. The catechin mechanism is plausible (antioxidant + anti-proliferative in lab settings) but human studies haven't consistently confirmed cancer-prevention claims at the level cardiovascular has been confirmed.

Bottom line: if you're going to claim one health benefit with confidence, it's heart-protection. Most other claims (weight loss, brain function, immune support) have some evidence but smaller effect sizes than the marketing suggests.

What makes Japanese green tea specifically healthier than Chinese or Indian green teas?

Two factors. First, Japanese tea is steamed within hours of harvest while Chinese green tea is mostly pan-fired. Steaming preserves more catechins and locks them in their natural form; pan-firing causes some oxidation. The catechin total per gram is typically 15-25% higher in Japanese sencha than in equivalent-grade Chinese green tea.

Second, the Japanese cultivation tradition leans toward shaded teas (matcha, gyokuro, kabusecha) which convert catechins into L-theanine — that's not better for antioxidant load specifically, but L-theanine has its own well-documented benefits for stress reduction, focus, and possibly cognitive aging. The gyokuro (玉露) + matcha combination delivers the highest L-theanine concentrations of any tea you can buy.

Indian and Sri Lankan teas are mostly black teas (fully oxidized), which is a different category — the catechin content is much lower because oxidation converts catechins into theaflavins and thearubigins. Those have their own health properties but are not interchangeable with green-tea catechins.

What is the Green Tea Steaming Process?
What is the Green Tea Steaming Process?

Is green tea actually anti-inflammatory, or is that wellness marketing?

It's real but smaller than the marketing suggests. EGCG inhibits several inflammatory pathways (NF-κB, COX-2, iNOS) at high doses in lab studies — the molecular mechanism is well-established. Whether you can drink enough green tea to produce a clinically-meaningful anti-inflammatory effect at human-realistic intakes is a different question.

In practice, daily green tea (3-5 cups) produces small reductions in inflammatory markers (CRP, IL-6) over weeks-to-months. The effect is enough to count cumulatively for chronic-disease risk reduction but not enough to substitute for actual anti-inflammatory medication when you have an active inflammatory condition. Tea is supportive, not therapeutic, for inflammation.

If you're managing autoimmune disease, arthritis, or any condition where inflammation is the central problem, daily green tea can stack with your treatment but won't replace it. Don't drop NSAIDs or biologics for tea; do drink tea alongside.

Does green tea actually help with weight loss the way it's marketed?

It contributes a small amount, much less than the marketing implies. Meta-analyses of green tea + weight loss studies typically show 1-2 kg of additional weight loss over 12 weeks compared to placebo — meaningful in research, mostly invisible in everyday life. The mechanisms are real (mild thermogenesis, slight fat oxidation increase, mild appetite effect from L-theanine + caffeine), but the effect size is small.

Where green tea actually does meaningful weight-management work is as a beverage replacement. If you're drinking green tea instead of soda, juice, or sweetened coffee drinks, the calorie reduction matters far more than the catechin effect. Replacing a 200-calorie sweetened latte with a zero-calorie green tea is real weight management; adding green tea to an unchanged diet is mostly hopeful.

Honest summary: green tea is a tool that supports an already-improving diet, not a fat-burning supplement. Treating it as the latter sets you up for disappointment.

How long does it take to see real health benefits from drinking green tea?

Acute benefits (focus, alertness, mood) hit within 30-60 minutes of the first cup — that's the L-theanine + caffeine combo working. Sustained benefits show up over very different timescales depending on what you're measuring.

Cholesterol and blood-sugar markers: 4-8 weeks of daily intake (3-5 cups). Weight management effect: 8-12 weeks. Cardiovascular outcomes: years to decades — the major epidemiological studies showing reduced heart-disease risk follow people for 5-15+ years. There's no fast version of cardiovascular risk reduction; consistency over years is the actual mechanism. The Sencha Lover Gift Set is a clean entry point if you want to find a daily tea you'll actually keep drinking — consistency is the only thing that delivers the long-arc benefits.

If you're starting fresh, give it a month at 3 cups daily and see how you feel before deciding it works or doesn't. Most acute benefits will be obvious by then; the long-game benefits accumulate quietly.

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About the author

Kei Nishida

Kei Nishida

Author, CEO Dream of Japan

info@japanesegreenteain.com

Certification: PMP, BS in Computer Science

Education: Western Washington University

Kei Nishida is a passionate Japanese green tea connoisseur, writer, and the founder and CEO of Japanese Green Tea Co., a Dream of Japan Company.

Driven by a deep desire to share the rich flavors of his homeland, he established the only company that sources premium tea grown in nutrient-rich sugarcane soil—earning multiple Global Tea Champion awards.

Expanding his mission of introducing Japan’s finest to the world, Kei pioneered the launch of the first-ever Sumiyaki charcoal-roasted coffee through Japanese Coffee Co. He also brought the artistry of traditional Japanese craftsmanship to the global market by making katana-style handmade knives—crafted by a renowned katana maker—available outside Japan for the first time through Japanese Knife Co.

Kei’s journey continues as he uncovers and shares Japan’s hidden treasures with the world.

Learn more about Kei Nishida

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