And it's not just the Eastern Asia favourite, green tea, that's good for our health. Although it's the green brew that usually gets the spotlight, other types of tea-from black to white to oolong-are proving to have powerful medicinal properties and may even be useful alternatives to drugs.
The most popular tea in the West as well as in South Asian countries such as India and Sri Lanka, black tea accounts for about 80 per cent of the world's tea production. As a fully fermented tea (see Factfile), black tea is dark in colour and full in flavour.
Assam, Ceylon and Darjeeling are well-known varieties, named after the regions in which they are produced. Black-tea blends such as English Breakfast tea, designed to go well with milk and sugar, are by far the most popular type of tea drunk in the UK.
Although green tea is the type of tea associated with the most health benefits, recent research suggests that black tea is good for you too. While green tea contains powerful antioxidant 'catechins'-thought to be responsible for its beneficial effects-black tea contains compounds called 'theaflavins', which are also potent antioxidants. Antioxidants are substances that can protect your cells against the effects of damaging free radicals, specific molecules thought to play a role in numerous diseases and conditions.
Black tea theaflavins have been shown to have anticancer, anti-bacterial, anti-inflammatory and antidiabetic effects in animal and test-tube studies, while a growing number of human trials suggest that drinking black tea can boost both the body and mind.
In one study by University College London scientists, men who drank black tea were able to de-stress quicker (as measured by looking at their levels of the stress hormone cortisol) following a stressful task compared with men who drank a tea substitute. This has important health implications, according to the researchers, as slow recovery after short-term stress has been linked to a greater risk of certain chronic conditions such as heart disease (Psycho-pharmacology [Berl], 2007; 190: 81-9).
In fact, heart disease is one of the main conditions black tea seems to protect you from. In a study of over 3000 adults in Saudi Arabia-where black tea is favoured over green-those who drank more than six cups of black tea daily had a 50-per-cent lower risk of heart disease that those who didn't drink tea (Prev Med, 2003; 36: 64-70).
Another study found that drinking black tea can help to reverse the abnormal functioning of the blood vessels that can contribute to stroke or heart attack (Circulation, 2001; 104: 151-6).
If you add milk to your tea, however, you might be destroying some of the drink's healthy effects. In a small German study, drinking black tea significantly improved the ability of the arteries to relax and expand to keep blood pressure healthy. But the addition of milk to the tea, thanks to milk proteins called 'caseins', blunted these effects completely (Eur Heart J, 2007; 28: 219-23).
Popular in East Asian countries such as China and Japan, oolong is a semi-fermented tea with an appearance and taste somewhere between that of green and black tea. It offers similar health benefits to green tea, so if you can't stand the taste of the green stuff, try a cup of oolong instead.
One benefit of drinking the tea appears to be weight loss. In a study of 100 overweight men and women conducted in China, drinking oolong tea was found to significantly reduce body fat and weight after just six weeks, which the researchers said was down to improved fat metabolism. They concluded that regularly drinking a cup of oolong could help to protect against obesity (Chin J Integr Med, 2009; 15: 34-41).
Oolong also appears to have a positive effect on the brain-and not just because it contains the stimulant caffeine. In a study of over 700 Chinese adults taking part in the Singapore Longitudinal Aging Studies (SLAS), those who reported regularly drinking tea-whether oolong, black or green-scored better on mental performance tests, such as memory and attention, compared with non-tea drinkers and those who drank coffee (J Nutr Health Aging, 2010; 14: 433-8).
Another study involving SLAS participants reported that regular tea-drinkers-especially those who drank oolong or black teas-had lower risks of mental impairment and decline. Again, there were no such benefits associated with drinking coffee, suggesting that something other than caffeine is responsible for the apparently brain-boosting effects (Am J Clin Nutr, 2008; 88: 224-31).
Yet another advantage of oolong is that it seems to be a good drink to choose after a meal if you suffer from heartburn. A Korean study investigated the amount of heartburn produced by a range of popular drinks, including oolong tea, coffee, alcohol and carrot juice. Oolong tea (along with carrot juice) had the lowest heartburn scores out of all the drinks tested (Korean J Gastroenterol, 2010; 55: 109-18).
A speciality of the Fujian province of China, white tea is an unfermented tea with a light and delicate flavour. Like green tea, white tea is rich in catechins, and research suggests that it has powerful antioxidant, anticancer and immune-boosting properties, too (J Food Sci, 2010; 75: C541-8). It may also be a useful weapon in the battle against ageing.
In one of the latest studies to look at white tea, researchers from Kingston University in London tested a freeze-dried powder extract of the tea on human skin cells. The results showed that white tea prevented the actions of the enzymes that break down elastin and collagen, which can lead to wrinkles. These enzymes, along with oxidants, are also associated with inflammatory disorders such as rheumatoid arthritis and cancer (J Inflamm [Lond], 2011; 8: 27).
Although such laboratory findings don't always apply to real life, lead researcher Professor Declan Naughton said that "drinking a simple cup of white tea might well help reduce an individual's risk of cancer, rheumatoid arthritis or even just age-associated wrinkles".
Other studies of human cells suggest that white tea can kill lung cancer cells (Cancer Prev Res [Phila], 2010; 3: 1132-40), protect brain cells (Neurotox Res, 2011; 20: 372-8) and trigger the breakdown of fat cells (Nutr Metab [Lond], 2009; 6: 20).
The perfect cuppa
As the benefits of different types of tea are becoming more and more well known, researchers are turning their attention to what makes the perfect cup of tea for reaping the best rewards of this healthful drink. While some are looking at precisely what effect milk has on the beneficial compounds in tea, others are investigating what happens when other ingredients are added to tea, such as lemon juice. In fact, one study found that green tea might be up to five times healthier if it's served with a dash of lemon juice, because the juice protects the health-boosting catechins from being digested in the stomach (Mol Nutr Food Res, 2007; 51: 1152-62).
As for how not to take your tea, it seems best to skip the sugar (and artificial sweeteners) and avoid a steaming hot cuppa. A study published in the British Medical Journal reported that drinking tea hot-at 65 degrees C or higher-was associated with a significantly greater risk of oesophageal cancer compared with drinking warm or lukewarm tea (BMJ, 2009; 338: b929).
Factfile: Tea types explained
Tea is a name given to many brews, but purists consider only those derived from the Camellia sinensis plant, a shrub native to China and India, as the real thing. The different types of tea-of which green, black, white and oolong are the most commonly drunk-are the result of differences in the methods by which the fresh leaves of C. sinensis are transformed into dried leaves for brewing.
Once picked, tea leaves immediately begin to wilt and oxidize-a chemical process known as 'fermentation' in the tea world. Whether a tea ends up as black, white or any other type depends on how long it is allowed to ferment. Green tea is produced from leaves that are unwilted and unfermented, white tea is from leaves that are wilted and unfermented, oolong is from leaves that are wilted and partly fermented, and black tea is from leaves that are wilted and fully fermented.
Because green and white teas involve little processing, these brews are richest in disease-fighting catechins. As the tea leaves ferment, the levels of catechins decrease, although levels of other healthy compounds, such as theaflavins and thearubigins, increase.
Interestingly, decaffeination reduces the total amount of catechins in both black and green dry teas by around 15 times and three times, respectively.
Factfile: Green tea goodness
Green tea is the most scientifically researched type of tea and is well deserving of its healthy image. Studies suggest that it can:
- lower blood pressure, cholesterol and the risk of heart disease-related death
- prevent age-related bone loss and reduce fractures
- cut the risk of type 2 diabetes
- help with weight loss and especially fat loss
- reduce tooth decay and prevent gum disease, and
- prevent and even treat certain types of cancer, including blood, liver, lung and prostate cancers (WDDTY vol 20 no 7).
WDDTY VOL. 23 NO. 1, APRIL 2012