the caffeine content of tea

> Caffeine accounts for tea’s energizing/uplifting qualities and isn’t necessarily bad for you!
> Studies are beginning to indicate that caffeine in small doses can be beneficial. A study
about the health benefits of green tea found that the caffeine is an active ingredient in
helping your system assimilate the antioxidants.
> Caffeine stimulates the central nervous system, promotes circulation and assists
the release of waste products.

approximate caffeine content of coffee and teas (milligrams per cup):
> drip coffee                   60-90mg
> black tea                     25-110mg          
> semi-green/oolong tea   12-55mg           
> white tea                    8-16mg
> green tea*                   8-16mg

The range above depends on the variety of tea and how long you steep it for. A shorter steeping time equals less caffeine. If you like strong flavour, but want to avoid caffeine, use more tea leaves and steep for a shorter time. Caffeine starts to release after about a minute.

*Matcha is an exception to this range because it can be prepared in two ways, and can contain as much caffeine as black tea, depending on how much powder is used.

Researchers have discovered that white tea contains marginally higher levels of caffeine compared to green tea brewed under the same conditions. They suggested that this could occur because white tea oxidizes slightly during withering; whereas, the oxidation process is stopped early in the manufacture of green tea by the steaming or pan firing of the leaves.

Since the term "antioxidant" is similar to "oxidation", it's important to clarify further what each represents. Both have a relationship to oxygen. Oxidation describes the process of combining a substance with oxygen. Black, semi-green and white teas are "oxidized" because they are exposed to air immediately after picking, prior to being dried. An "antioxidant" is a substance such as vitamin e, c or beta carotene which inhibits oxidation. They are believed to have health benefits because they protect the body's cells from the damaging effects of oxidation.

Tea naturally contains antioxidants, and the level of antioxidants found in tea is not as a result of the oxidation process. "Oxidation" is just a way to describe how black, semi-green and white teas are processed. Exposure to air is what causes changes to occur in the leaf, making it look and taste different, as well as increasing the caffeine content.

the caffeine in tea affects you differently than the caffeine in coffee:
> Coffee gives you a very fast lift, but an equally sharp decline in your energy is felt later.
> Tea gives you a slower, more delayed lift, which leads to a plateau, and then a secondary lift.
> Tea does not give you a sharp decline, rather it very gradually decreases so you don’t feel the negative effects of the decrease in the way it is felt with coffee.
> Black and semi-green teas are a good way to wean yourself off of coffee; you can start out by continuing to drink a cup of coffee in the morning and following it up with a black or semi-green tea in the afternoon.

a note about the caffeine and nutritional value of teabags:
> Teabags release up to twice as much caffeine as loose teas because they are made with low grade leaves that are powdered and crushed up.
> As soon as a tea leaf is crushed, the surface area of the leaf is exposed to more air, which causes the tea to lose nutrient value, go stale and lose flavour rapidly.*
> To counteract loss of flavour, more crushed leaves are used, which equals more caffeine.
> Teabags are generally made with low-grade leaves (the twigs, leaves, stems that are located lower on the tea bush) as opposed to the “top” leaves and bud that are used for high quality loose teas. The lower grade leaves contain less nutrient value, not solely because they are crushed, but also because they are poorer quality to start out with.
> Many estates produce their entire low-grade tea yield solely for teabag production, and some teabag manufacturers also use leftovers from high-grade tea production (crushed and broken leaves).
> Teabags are made with glue to hold the bag together when it hits the water.

*Matcha is the only tea that does not lose flavour or health benefits when the leaves are crushed. Matcha is powdered under very stringent controls, which are designed to keep it fresh and nutrient rich. Its exposure time to air is deliberately very minimal. The same attention is not paid to crushed leaves used for teabag teas.