About tea

All true teas — white, green, oolong, and black — come from a single plant: Camellia sinensis, an evergreen shrub native to East Asia. What distinguishes one tea from another is not the plant itself, but how the leaves are harvested and processed after picking.

The four main categories of true tea represent different points along a spectrum of oxidation — the natural process by which enzymes in the leaf react with oxygen when the leaf is bruised or broken. White teas undergo the least processing; black teas are fully oxidised. Green and oolong teas fall between these two extremes.

Herbal infusions — including rooibos, honeybush, and yerba maté — are not made from the Camellia sinensis plant and are more accurately described as tisanes. They are naturally caffeine-free (in the case of rooibos and honeybush) or lower in caffeine, and each carries its own distinct flavour profile and nutritional properties.

One of the most well-documented qualities of tea is its high antioxidant content. Antioxidants are compounds that help neutralise free radicals — unstable molecules produced naturally through metabolism, as well as through exposure to environmental stressors such as UV light, pollution, and smoke. Over time, unchecked free radical activity is associated with cell damage and a range of chronic conditions.

Tea is particularly rich in a class of antioxidants called polyphenols, which include flavonoids and, in green tea specifically, catechins such as epigallocatechin gallate (EGCG). A standard cup of tea contains over 140mg of antioxidants — more than twice the amount found in a single apple. Research suggests that regular tea consumption may meaningfully increase antioxidant levels in the bloodstream.

Vitamins A, C, and E are also present in tea and contribute additional antioxidant activity. Tea is furthermore a useful source of fluoride and potassium, which support dental health and normal fluid balance respectively.

The concentration of antioxidants in your cup is influenced by brewing time, water temperature, and whether you use loose leaf or bagged tea. See our Brewing Guide for full guidance on getting the most from every cup.

A common misconception is that tea acts as a diuretic, negating its contribution to daily fluid intake. Research does not support this view at normal drinking volumes. Studies show that drinking 3–4 cups of tea per day contributes positively to hydration, comparable to water. The mild diuretic effect of caffeine is offset by the high water content of the beverage when consumed at standard strengths.

Potassium, naturally present in tea, also supports the body's fluid regulation. Only very high caffeine intake — well beyond typical tea-drinking quantities — would have a meaningful diuretic effect.

Caffeine occurs naturally in the leaves of Camellia sinensis, as it does in coffee, cacao, and cola. It is one of the most widely consumed psychoactive compounds in the world and, at moderate intake levels, is well-tolerated by most healthy adults.

A standard cup (190ml) of black tea contains approximately 25–50mg of caffeine — roughly half the amount in a cup of instant coffee. The polyphenols in tea are believed to slow the rate of caffeine absorption, producing a more sustained, gradual effect compared to coffee.

Tea Type	Caffeine per cup (approx.)
Black tea	25–50mg
Oolong tea	15–40mg
Green tea	15–30mg
White tea	10–30mg
Yerba maté	20–40mg
Rooibos	0mg
Honeybush	0mg

Food Standards Australia New Zealand (FSANZ) advises that most healthy adults keep caffeine consumption below 400mg per day. For pregnant women, a more conservative limit of 200mg per day is widely recommended by health authorities including FSANZ, the European Food Safety Authority, and the UK's NHS.

For those looking to reduce caffeine intake, lighter oolongs, green teas, rooibos, and honeybush are all excellent options.

Rare, minimally processed, and exceptionally delicate, white tea is produced primarily in the Fujian province of China. Only the youngest, most tender leaf buds — covered in fine silvery hairs — are hand-plucked for just a few days each spring. After a simple steaming and drying process, the result is one of the purest tea forms available.

White tea infuses to a pale, almost translucent liquor with a fresh, mellow, and naturally sweet flavour — none of the grassiness sometimes associated with green teas.

Because of its minimal processing, white tea retains very high levels of polyphenol antioxidants. Some research suggests white tea may offer antioxidant activity comparable to, or greater than, green tea, though large-scale human studies remain limited. White tea is naturally low in caffeine, making it a good option for those managing their intake.

Well-known varieties include Silver Needle (Bai Hao Yinzhen), White Peony (Pai Mu Tan), and Jasmine Silver Tips.

Green tea has been consumed across China and Japan for thousands of years, and it is among the most extensively studied foods in nutritional research. After picking, the leaves are quickly heated — steamed in the Japanese tradition, pan-fired in the Chinese — to halt oxidation and preserve their natural colour and high antioxidant content.

Green tea is low in caffeine and notably rich in catechins, particularly EGCG. It also contains fluoride, potassium, and vitamins A, C, and E. A substantial body of research has explored green tea's potential associations with cardiovascular health, metabolic function, dental health, and immune support. While results are encouraging, researchers generally note that most findings come from observational studies or laboratory settings, and further controlled human trials are needed.

Green teas produce light, bright infusions with crisp, slightly astringent flavours best enjoyed without milk or sweetener, which can mask their character.

Notable varieties include sencha, matcha, houjicha, gyokuro (Japan), and gunpowder and lung ching (China).

Oolong sits between green and black tea in terms of oxidation — a fascinating middle ground that produces some of the world's most complex and sought-after teas. Originating in the Fujian mountains of China and later refined in Taiwan, oolongs are always whole-leaf teas that undergo a carefully managed process of wilting, bruising, and partial oxidation before firing.

Chinese oolongs are typically 15–20% oxidised, producing pale, golden-amber liquors with floral or peachy notes. Taiwanese oolongs are 60–70% oxidised, yielding richer, darker brews with a deeper flavour profile.

Oolongs carry more caffeine than green tea but less than black, and share many of the same polyphenol antioxidants found across the true tea family.

Highly regarded varieties include Tie Guan Yin, Big Red Robe (Da Hong Pao), Buddha's Hand, Tung Ting, and Formosa oolong.

Black tea is fully oxidised, which gives it its characteristic dark leaves, rich aroma, and bold, full-bodied flavour. It is the most widely consumed tea category in the Western world and the base for classic blends such as English Breakfast, Assam, Darjeeling, and Earl Grey.

Black teas are graded by leaf size, quality, intactness, and tenderness:

• Broken Pekoe (BP) — very small or broken leaf pieces
• Broken Orange Pekoe (BOP) — quality leaf intentionally cut to release flavour quickly
• Pekoe (P) — short, whole leaf pieces
• Orange Pekoe (OP) — longer, higher quality whole leaf
• Flowery Orange Pekoe (FOP) — leaf buds with one new leaf attached
• Tippy Golden Flowery Orange Pekoe (TGFOP) — high proportion of golden-tipped buds
• Finest Tippy Golden Flowery Orange Pekoe (FTGFOP) — predominantly young, tender, golden-tipped buds

Higher-grade whole-leaf black teas withstand longer infusions, allowing higher concentrations of antioxidants to develop. Black tea contains roughly half the caffeine of instant coffee, and the polyphenols in tea are believed to slow caffeine absorption, producing a more gradual, sustained effect.

Rooibos (pronounced "roy-boss") is produced exclusively from Aspalathus linearis, a shrub native to the Cederberg Mountains of South Africa's Western Cape. Its needle-like leaves produce a smooth, naturally sweet, slightly fruity infusion with a gentle caramel character.

Red rooibos (fermented) is the most familiar form, with a warm amber colour and mild sweetness. Green rooibos (unfermented) has a lighter, slightly more complex flavour and higher antioxidant content.

Rooibos is completely caffeine-free and very low in tannins, which means it does not become bitter with extended brewing and will not interfere with iron absorption. It is suitable for all ages, including young children and pregnant women.

Laboratory and animal studies suggest rooibos has significant antioxidant activity, comparable in some respects to green tea, though large-scale controlled human studies are limited. It is traditionally associated with supporting immunity, digestion, and restful sleep.

Honeybush (Cyclopia intermedia) is an evergreen shrub grown on the mountain slopes of South Africa's Eastern Cape. Similar in appearance to rooibos, it produces a pinky-red liquor with a naturally sweeter flavour — a characteristic intensified by harvesting during the plant's flowering season.

Like rooibos, honeybush is caffeine-free, low in tannins, and entirely suitable for children and those sensitive to stimulants. It contains calcium, manganese, potassium, and a range of polyphenol antioxidants, some of which are found only in honeybush.

Research into honeybush is less extensive than for true teas or rooibos. Many of the health associations attributed to it are based on traditional use and a modest number of studies. Early scientific findings suggest potential antioxidant, anti-inflammatory, and phytoestrogenic activity, though further human trials are needed before firm conclusions can be drawn.

Honeybush withstands long infusions well and can even be gently simmered to intensify flavour. It also works well in cooking as a substitute for liquid stock.

Derived from the leaves of Ilex paraguariensis, a South American evergreen holly, yerba maté (pronounced "mah-tay") has been consumed for centuries across Argentina, Brazil, Paraguay, and Uruguay — often as a shared cultural ritual. It has seen growing international interest, particularly among health-conscious consumers seeking an alternative to coffee.

Maté contains a broad nutritional profile: over 190 active compounds have been identified, including polyphenol antioxidants, saponins, and a range of vitamins and minerals. It contains caffeine — generally less than coffee or black tea — and some researchers suggest a compound called mateine may contribute to its characteristic stimulating effect: alertness and mental clarity without the jitteriness sometimes associated with coffee.

Maté has a slightly astringent, bitter character that can be balanced with sweeteners or fruit flavours. Traditional preparation uses a gourd and metal straw (bombilla).

Please note: Very high and frequent consumption of very hot maté has been associated in some observational studies with increased risk of oesophageal cancer. This association appears to relate to the extremely high temperature of consumption rather than to maté itself. Drinking maté at a sensible temperature removes this concern.

Regular tea drinking has been associated with a range of potential health benefits, largely attributed to its high concentration of polyphenol antioxidants. These compounds — including flavonoids, catechins, and other phytochemicals — are the subject of a growing body of scientific research.

A cup of tea contains over 140mg of antioxidants, and research suggests that drinking three cups a day for two weeks may increase specific antioxidant concentrations in the blood by around 25%. In combination, tea's chemical components have shown potential in laboratory and observational research across a number of areas including cardiovascular health, metabolic function, immune response, and dental health.

Tea's antibacterial, antifungal, and antiviral properties have also been noted in research settings, with some studies suggesting a supportive role in immune resilience. Three to four cups of tea per day provides around 45% of recommended daily fluoride intake, which may contribute to bone density, reduced tooth decay, and limits on bacteria associated with bad breath.

As with all dietary research, tea consumption should be considered as part of an overall healthy diet and lifestyle, not as a standalone intervention.

Research has explored the relationship between regular tea consumption and cardiovascular health for several decades. Studies suggest that the flavonoids and flavonols found in high concentrations in both black and green tea may support heart health in a number of ways — including improving blood vessel function, reducing LDL oxidation, inhibiting platelet aggregation, and providing anti-inflammatory activity.

A body of observational research suggests that drinking 2–3 cups of tea per day as part of a balanced diet is associated with a modest reduction in risk of cardiovascular disease and stroke. A 2013 meta-analysis published in the European Journal of Preventive Cardiology found a significant inverse association between green tea consumption and cardiovascular disease mortality.

It is important to note that most of the underlying mechanisms have been established in laboratory and animal studies. Observational studies in human populations are consistent and encouraging, but cannot establish direct causation. The current scientific view is that regular tea consumption can form a sensible part of a heart-healthy diet — alongside other dietary and lifestyle factors.

Cancer research and dietary science are inherently complex fields, and we present this information accordingly. The World Cancer Research Fund estimates that up to 30–40% of cancers may be linked to dietary and lifestyle factors — an area that has generated significant scientific interest, including research into tea.

Polyphenol antioxidants in tea, particularly catechins in green tea, have been studied in laboratory and some clinical research for their potential role in reducing oxidative stress associated with cancer development. Observational studies have explored possible associations with certain cancer types, including bladder, colon, oesophageal, prostate, and stomach cancers.

Results are often encouraging but remain inconclusive at the level of controlled human trials. More recent research suggests that other true teas — black, white, and oolong — may offer different but comparable antioxidant properties to green tea, and that rooibos and honeybush also show meaningful antioxidant activity in laboratory settings.

The current weight of evidence suggests that a diet rich in plant-based antioxidants — of which quality loose leaf tea can form a meaningful part — is broadly associated with reduced cancer risk. Tea should not be presented or interpreted as a cancer treatment or specific preventive agent.

Type 2 diabetes is characterised by the body's reduced ability to regulate blood glucose, either through insufficient insulin production or reduced cellular response to insulin. Diet and lifestyle play a significant role in both the risk of developing type 2 diabetes and in managing its progression.

Early research has identified several compounds in tea that may influence insulin activity and glucose metabolism. EGCG, found in high concentrations in green tea, has shown insulin-enhancing properties in laboratory studies and may mimic some aspects of insulin activity while also influencing the liver's production of glucose. Catechins may also reduce the rate at which glucose is absorbed through the intestinal wall.

Observational studies in human populations have found associations between regular green and black tea consumption and a modestly reduced risk of type 2 diabetes, though results vary across different study populations. Benefits appear to be associated with regular, sustained consumption.

Some research suggests that adding milk to tea may reduce certain bioactive effects, though the evidence on this is not conclusive. Lemon juice does not appear to have a negative effect.

If you want something bold and familiar: Start with a quality Assam, English Breakfast, or single-origin black tea. Add milk and no sugar — let the quality speak for itself.

If you want to reduce caffeine but keep flavour: Try a lightly oxidised oolong or a quality single-estate green tea. Both offer complexity with less caffeine than black tea.

If you want caffeine-free: Rooibos or honeybush are excellent all-day options with genuine flavour and good antioxidant content. Both are naturally sweet and smooth.

If you are pregnant: Rooibos or honeybush are ideal. If you prefer a true tea, a single daily cup of quality green tea keeps caffeine well within safe limits.

If you are focused on antioxidant content: Green tea has the most extensive research behind it. Matcha (powdered whole-leaf green tea) delivers the highest concentration of catechins per serving, as you consume the whole leaf.

If you want something rare and memorable: A good white tea — particularly Silver Needle — is an exceptional experience and a genuine conversation piece.

The quality of your tea is inseparable from where and how it is grown. At t leaf T, our supplier relationships have been built over more than 20 years, grounded in trust, shared values, and an unwillingness to compromise on quality or integrity.

We source from growers and producers who share our commitment to sustainable land management, fair treatment of workers, and the preservation of the regional tea-growing traditions that make each cup distinctive. Many of our teas carry BioGro organic certification.

We are a 100% New Zealand-owned family business, and the choices we make as buyers matter — both for the people who grow our tea and for the customers who drink it.