The British response to a stressful situation is to reach for the kettle and get out the teabags. Recently, researchers have confirmed that our response to drama amounts to more than psychology. Scientists at University College London found that drinking tea lowers post-stress levels of cortisol, the hormone released when we experience physical or emotional trauma and which increases blood pressure and makes our hearts race.

The study, published in the journal Psychopharmacology, took 75 healthy non-smoking men and made them give up their usual tea, coffee and caffeinated beverages such as energy drinks for four weeks before the study. They were then subjected to “stress tests”. These included being accused of shoplifting and threatened with job loss. Levels of cortisol were measured before, during and after.

Next, 37 men were asked to drink four cups a day of tea-coloured fruit drink which contained all the active constituents of a cup of black tea. The other 38 drank a teacoloured placebo.

When the stress tests were repeated after six weeks on this regime, it was found that the cortisol levels of those drinking the fruit drinks fell more quickly and they scored lower on a subjective rating of how stressed they felt compared with those on the placebo “tea”.

Professor Andrew Steptoe, one of the leaders of the study, explains: “Tea contains a supernutrient called theanine which can block the action of excitatory nerve transmitters, lowering our overall stress responses. But it also contains a host of other bioactive compounds, many of which could be working together to be responsible for this effect.” One of these could be epigallocatechin gallate, which is known to be a mild sedative. While scientists tease out the fine detail, the result is clear — sipping four cups of tea a day acts as a stress-reducing buffer.

According to Dr Carrie Ruxton, author of a new report in the European Journal of Clinical Nutrition, there is now evidence to suggest that three cups a day reduces the risk of coronary heart disease thanks to its antioxidants. These are known as flavonoids and, although they are also found in onions and apples, tea is estimated to provide 82 per cent of our intake.

These, as Ruxton explains, can help to protect our hearts: “First, they seem to improve the function of the lining of blood vessel walls, making them relax slightly so that blood pressure is reduced. They also change the composition of the vessel walls, making it more difficult for cholesterol to attach and form fatty plaques that block blood flow. Finally, flavonoids can reduce bad LDL cholesterol by more than 11 per cent.”

The UK National Diet and Nutrition Survey (2002) indicates that on average we glug down 2.3 mugs a day, but it seems that many of us could do with an extra cup or two.

New research also suggests that the phenolic supernutrients in tea are not completely absorbed in our digestive systems but move into the colon, where they reduce growth of bad bacteria and act as a food source for good bacteria.

TEA: FACT OR FABLE

Does tea dehydrate?

A study in the European Journal of Applied Psychology helped to lay this myth to rest by looking at the dehydrating effects of tea on 13 members of an expedition on Mt Everest at an altitude of 5,345m (17,500ft). The climbers were chosen because altitude affects fluid balance. Over two 24-hour periods, they drank either tea or a placebo. Measures of dehydration were similar during both periods, so the researchers concluded that there is no evidence that tea is a diuretic.

Is tea high in caffeine?

Data based on 400 samples of tea from family homes, workplaces and shops in ten areas across the UK suggest that the average caffeine content of a 235ml cup of tea is 40mg (the longer it brews, the more caffeine it contains). Coffee supplies 75mg-100mg per cup. While large amounts of caffeine are related to rises in blood pressure, anxiety and insomnia, taking 40mg-60mg a day has been shown to help concentration and endurance, and to combat fatigue.

Is green tea better?

Green tea is made from the mature fresh tips of the tea plant, which are steamed, whereas black tea is made by fermenting its leaves. Green tea consequently contains more catechins — flavonoids that are especially well absorbed from the upper intestine. They have been shown to have antioxidant, antibacterial and immune system regulating effects. Some small studies have indicated that five to six cups of green tea daily can slightly raise the metabolism and increase calorie burn by around 80-100 a day.

What is white tea?

White tea is made from the buds and young leaves, immediately steamed post harvest. They retain high concentrations of catechins. It is a speciality of the Fujian province of China and is available in some supermarkets and speciality tea shops. A study has suggested that it has a greater antimicrobial effect than green tea.

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