Tea - stimulant

It is unlikely that tea would have been so popular through the ages without its special component, caffeine. This stimulating compound helps keep us awake, gives us energy, improves our mood and enhances our ability to think clearly.

Caffeine

Caffeine is a unique drug. Because it is water soluble, it permeates the body's cells with ease. It quickly transfers from the digestive system to the blood which carries it to other organs. Within an hour after finishing your cuppa, the concentrations of caffeine are virtually the same in all parts of your body including blood, saliva and even breast milk. This ease at which it is absorbed into the body is the key to its success. Unlike many other drugs, caffeine easily passes into the cells of the central nervous system and the brain. The caffeine is converted into secondary products by the liver, and is finally excreted in urine.

Effects on the body

An old photograph of a rolling machine in a tea factory from the 1930s.
This rolling machine compresses the withered leaves to release their juices, the tea is then left to ferment, 1930s.

Although caffeine's stimulating effects on the body are not fully understood, research has uncovered many explanations. The latest shows that caffeine interferes with adenosine, a sleep-inducing chemical in the body which makes us feel drowsy. Caffeine blocks the effects of adenosine which prevents us from dropping off to sleep. In turn, the body becomes more active and thinks some sort of emergency might be occurring, so it produces adrenaline. This is the 'fight or flight' hormone, and it has a number of effects on your body including increasing heartbeat and blood flow to muscles and releasing sugar in the bloodstream for extra energy.

Sources of caffeine

Caffeine is more accessible now than ever before. It exists naturally in other plants such as coffee (Coffea species), cocoa (Theobroma cacao) and guarana (Paullinia cupana). 'Waste' caffeine extracted from decaffeinated teas and coffees has become an ingredient in soft drinks including Coca-Cola, and the more potent, energy-giving Red Bull. It is also freely available as anti-tiredness pills and added to some over-the-counter or prescription medicines like pain relievers, cold remedies and appetite suppressants. It is even added to body contouring creams to reduce cellulite, though there is no scientific evidence that this really works.

Caffeine levels are lower in tea than coffee, and different teas contain different levels of caffeine. The lengthier the fermentation process, the greater the caffeine content. So green tea has the least caffeine while black tea contains the most. The caffeine content of the final drink is also increased by using tea bags over loose leaf tea and by brewing it for longer.

Safety

Caffeine's popularity is a concern for some. Research shows that it could have potentially harmful effects to health. But despite the rise in popularity of decaffeinated drinks in recent years, it is generally understood that caffeine is safe at moderate levels of consumption. Whether taken as a hot cuppa, fizzy drink or pill, caffeine consumption today is more widespread than ever.