Green Tea & Antioxidants: What the Research Says

A Brief History of Green Tea

Green tea has been consumed in China for well over 4,000 years, with historical records suggesting it was first used as a medicinal beverage before becoming a daily drink. It spread to Japan around the 9th century via Buddhist monks, who cultivated a rich culture of tea preparation and ceremony that continues to influence how the world drinks tea today.

Today, green tea is one of the most widely consumed beverages on the planet, second only to water in some regions of Asia. Its global popularity has driven a significant body of scientific research into its chemical composition and potential effects on human health.

What Are Antioxidants?

Antioxidants are compounds that can inhibit or slow oxidation — a chemical reaction that can produce free radicals, which are unstable molecules that can interact with and damage cells. The human body produces some antioxidants naturally, but also relies on dietary sources to supplement them.

Common dietary antioxidants include:

• Vitamin C (found in citrus fruits, berries)
• Vitamin E (found in nuts, seeds, vegetable oils)
• Beta-carotene (found in carrots, sweet potatoes)
• Polyphenols (found in tea, berries, dark chocolate, olive oil)

Green tea is particularly notable for its high polyphenol content, specifically a group of compounds called catechins.

Catechins: Green Tea's Key Polyphenols

Catechins are a type of natural polyphenol and antioxidant found abundantly in green tea. The most significant catechin in green tea is epigallocatechin gallate (EGCG), which accounts for the majority of catechin content in most green teas and has been the subject of extensive scientific study.

The catechin content of green tea varies significantly depending on growing conditions, the age of the leaves at harvest, processing methods, and how the tea is brewed. Generally, higher-quality, younger leaves (such as those used in gyokuro and tencha) have a higher catechin concentration.

Green Tea vs. Black Tea: Why Processing Matters

Both green tea and black tea come from the same plant — Camellia sinensis. The key difference is in how the leaves are processed after harvest.

Green tea leaves are quickly heated (by steaming in Japan or pan-firing in China) after picking to stop the natural oxidation process. This preserves the catechins and gives green tea its characteristic colour and flavour profile.

Black tea leaves, by contrast, are fully oxidised. During oxidation, the catechins are converted into other compounds (theaflavins and thearubigins), which give black tea its darker colour, richer flavour, and lower catechin content compared to green tea.

What Does the Research Say?

There is a substantial body of scientific literature on green tea and its polyphenol content. It is important to read this research carefully and with appropriate context:

Population Studies

Several large observational studies — particularly those conducted in Japan, where green tea consumption is among the highest in the world — have observed associations between regular green tea consumption and various health markers. These are observational studies, which means they can identify correlations but cannot establish causation.

Laboratory Studies

Many studies on green tea catechins have been conducted in vitro (in laboratory cell cultures) or in animal models. While these studies have produced interesting findings, results from cell culture and animal research do not always translate directly to human physiology.

Clinical Trials

A smaller number of randomised controlled trials (the gold standard of scientific evidence) have examined green tea or green tea extract in human subjects. Results have been mixed and often modest. Most researchers note that additional well-designed, large-scale clinical trials are needed before firm conclusions can be drawn.

The scientific literature on green tea is interesting and worth following — but the most honest summary is that green tea is a genuinely enjoyable, antioxidant-rich beverage with a long history of traditional use. Anyone with specific health concerns should consult a qualified healthcare professional.

How to Get the Most Catechins from Your Green Tea

If you would like to maximise the catechin content of your brewed green tea, the following brewing practices are supported by research:

• Use lower water temperature — Water around 75–80°C (167–176°F) extracts catechins effectively while minimising bitterness.
• Steep for 2–3 minutes — Longer steeping does not necessarily increase catechin content and may increase bitterness.
• Choose higher-quality leaves — Younger leaves (first and second flush) tend to have higher catechin concentrations.
• Drink it fresh — Catechin content in brewed tea decreases over time; drink within 30 minutes of brewing for best results.
• Avoid adding milk — Some research suggests that milk proteins may bind to catechins, reducing their bioavailability, though the evidence is debated.

Popular Green Tea Varieties

Not all green teas are the same. Here is a brief overview of some of the most popular varieties:

• Sencha — The most widely consumed green tea in Japan; bright, grassy, and slightly sweet.
• Matcha — A powdered form of shade-grown green tea (tencha); consumed whole rather than infused, making it higher in catechins per serving.
• Gyokuro — A premium Japanese green tea shade-grown for several weeks before harvest; sweeter and more complex than sencha.
• Longjing (Dragon Well) — A classic Chinese pan-fired green tea with a nutty, vegetal flavour.
• Gunpowder — Chinese green tea rolled into small pellets; bold and slightly smoky.

Browse our tea collection to explore premium green teas, or read our brewing guide to learn how to get the most from every cup.