I’m a coffee drinker myself, but have been a long-time fan of tea as a beverage that may bring benefits for the body. Tea is rich in substances called polyphenols that have ‘antioxidant’ activity (which means they have the capacity to neutralise the effects of damaging, destructive molecules called ‘free radicals’). Previous research has linked the consumption of tea with a reduced risk of heart disease, and perhaps some forms of cancer too. This month’s edition of the European Journal of Clinical Nutrition contains a British study in which the potential health benefits of tea have been reviewed. This study found that:
- drinking 3 or more cups of black tea a day appears to significantly reduce the risk of heart disease
- tea drinking does not appear to be associated with a reduced risk of cancer, except for colon cancer (and the protective effect here looks quite small)
- drinking tea does not tend to dehydrate the body, despite containing some caffeine and other substances that have a diuretic effect (meaning they stimulate urine production)
Overall, the results of this review suggest that tea is not harmful to health, and in fact appears broadly beneficial. This review focused specifically on black tea. Green tea (from which black tea is formed) has been found to contain higher levels of antioxidants, and therefore have more disease-protective potential. While the research suggests that drinking black tea is not particularly protective for cancer, studies have found green tea consumption is linked with a reduced risk of several forms of cancer including those of the breast and prostate. The evidence appears strong enough to recommend tea, particularly green tea, as a genuinely healthy beverage.
Observer column – 11th May 2003
A lot of the dietary advice that comes at us these days seems to ask us to forgo our favourite foods, or swallow more stuff we’re not partial to. Like most of us, I like an easy life, which is why I’m always on the lookout for good news about foods and drinks the consumption of which does not seem like a hardship, and may actually be enjoyed. In May of 2003, American researchers announced the results of a study which showed that tea can help boost the function of the immune system. Drinking tea was found to help immune system cells attack foreign invaders, an effect which clearly has the potential to keep infections at bay. It seems that stepping up our intake of the nation’s favourite cuppa might be just the right thing to do should we find ourselves with an infection brewing.
While downing a few mugfulls of tea at the first sign of fevered brow or sore throat may make good sense, longer-term consumption seems to have more profound benefits for the body. Tea is rich in a bewildering concoction of substances compounds including phenolic compounds, (such as caffeic acid, quinic acid and gallic acid), polyphenols (such as catechin, epicatchetin and epigallocatechin gallate), and flavonols (such as quercetin, kaempferol and rutin). Tea’s constituents have been found to have the capacity to ‘thin’ the blood, and also quell damage in the body caused by inflammation and disease-promoting entities called free radicals. This combination of effects should, in theory at least, afford some protection against the biggest killer in the West – heart disease.
Several studies have examined the relationship between tea drinking and heart disease. While not all studies suggest benefit, most do. One study published in 2003 found that compared to individuals drinking no tea, individuals drinking 6 or more cups of tea today had about half the risk of suffering from heart disease. Another study, published in 2002 in the American Journal of Clinical Nutrition, found that drinking 2 or more cups of tea each day was associated with a 43 per cent reduced risk of having a heart attack. This study also showed that tea drinkers were 70 per cent less likely to die from a heart attack compared to never-consumers. More evidence for the heart-related benefits of tea has came from a study of heart attack survivors. This research found that in the next few years after the heart attack, drinking two or more cups of tea a day appeared to reduce risk of dying by about 40 per cent.
While drinking tea does appear to be good for us, some moderation is probably warranted. Tea contains caffeine (about one third to one half the amount found in coffee), so at high intakes there is always the risk of effects signalling an excess of this stimulant in the system. Anxiety, heart palpitations and insomnia are the main symptoms to look out for. Other than that, however, it appears there is good news for the 70 per cent of the population who drink tea on a regular basis. If you’re one of them, you can take heart in the knowledge that doing something you enjoy might actually be doing you some good.
Observer column – 1st February 2004
Green tea ” the Oriental import that appears to offer protection from cancer
We British do seem to have an insatiable appetite for foreign cuisine, and one country whose traditional fare seems to have made a successful migration to these shores is Japan. While taste and fashion are likely to be driving forces in the rising popularity of Japanese food in these parts, my suspicion is that another contributory factor has been its healthy reputation. It is often said that the fish-rich nature of sushi and sashimi gives these foods disease-protective and life-extending properties. However, another Far East foodstuff that may help to explain the relative good health and longevity of the Japanese is green tea. Research has linked an increased consumption of this oriental infusion with a reduced risk of conditions such as cancer and heart disease. It seems there is good reason to consider green tea as much more than merely the flavour of the month.
Researchers seeking an explanation for green tea’s apparent health-giving qualities believe they have found it in the form of substances known as polyphenols. These constituents of the tea plant have what is known as ‘antioxidant’ activity, which means they have the potential to quell disease-promoting molecules known as free radicals. While green tea contains several polyphenols, research suggests that the most potent weapon in its armoury is likely to be a compound known as epigallocatechin gallate (EGCG). EGCG has been found to have a number of cancer-protective actions in the body, including an ability to help in the deactivation of cancer-causing chemicals (carcinogens).
The supping of green tea has been linked with a reduced risk of cancer in both men and women. In one study published in 2004, women drinking the equivalent of about half a cup of green tea a day were found to have a 47 per cent reduced risk of breast cancer compared to those drinking none at all. In another study published the same year, researchers found that men consuming three cups of green tea each day had about a quarter of the risk of prostate cancer compared to non-green tea drinkers. Other research has found that increased green tea consumption appears to protect against other forms of cancer too, including those of the stomach, colon, lung and skin.
The apparent liquid assets of green tea seem to extend to benefits for the circulatory system too. Research has found that individuals who consume green tea tend to have lower blood levels of cholesterol. A study published in the Journal of Nutrition in 2003 found that the drinking of green tea was associated with a significant lowering of blood pressure levels. These benefits go at least some way to explaining research which links green tea consumption with a reduced risk of stroke and heart disease.
While consumption of this big-in-Japan beverage is on the rise in the UK, we mostly elect to drink tea in its black form – itself made by subjecting green tea to a process of fermentation. The fermentation of green tea causes the chemical conversion of much of its EGCG into compounds that seem to offer more muted benefits for the body. While studies show that that black tea has the potential to benefit health, the research suggests that it’s green tea that deserves the cup.