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A porcelaine cup of power
August 14, 2007
Already known for its health benefits, tea now seems to be an effective deterrent against a myriad of diseases
Rosie Schwartz, National Post
Published: Tuesday, August 14, 2007
Scientists all over the world have been investigating tea leaves to see what the future holds. And according to a wealth of accumulating evidence, they’re predicting potential good health for those who regularly imbibe—tea, that is.
But not all teas are created equal. First off, herbal teas are not actually teas at all. These tisanes—their more accurate name—are infusions of herbs or plant leaves and aren’t related to the botanical family of true teas. Although research shows that they may offer a range of health benefits, they’re not what the buzz over tea is all about. And green tea, which many believe to be an herbal tea, is actually a full member of the real-tea clan. Green as well as oolong and black tea come from the Camellia sinensis plant. White tea, which has more recently made its appearance in Western tea cups but dates back many centuries in China and Japan, is also a family member.
The differences among the teas are due to the varied ways they’re processed, including the amount of oxygen exposure following their harvest. The white variety is made up of only buds rather than tea leaves, and it is not oxidized at all. Green tea contains only the leaves, which, after picking, are immediately steamed or heated to prevent oxidation (as with white tea) and then dried. Black teas, on the other hand, experience maximum oxygen exposure, which yields a darker colour and a completely different aroma. The oolong varieties are partially oxidized, making them stronger than green tea but milder than black.
While a cup of tea may seem as simple a beverage as can be, it’s actually a complex brew of potential disease fighters. Among the compounds it contains are polyphenols, kissing cousins to the protective substances identified in red wine, chocolate and a variety of fruits and vegetables. Research is showing that each type of tea supplies a concentrated source of polyphenols, but also that each differs slightly in its impact on health. Also, be aware that a quick dip of the tea bag in hot water won’t yield maximum polyphenol levels. Instead, aim for a steep of at least three or four minutes.
The list of potential benefits of tea seems to be growing in leaps and bounds. Scientists have linked tea consumption to protection against common ills such as cardiovascular disease, certain cancers, high blood pressure and Alzheimer’s disease.
Tea’s action in protecting artery health provides insight into just how complex its disease-fighting weaponry actually is. First, some of the polyphenols in tea, called flavonoids, have been shown to reduce blood cholesterol readings. Also on the cholesterol front, some of these compounds defend against cholesterol being oxidized into the form of cholesterol that’s more easily deposited in arteries. In addition, the polyphenols protect the endothelium—the lining of the artery—making it more flexible as opposed to brittle and hardened. Better blood flow is the result. And if that’s not enough, tea is linked to better blood pressure readings.
Drinking a variety of teas may also help to battle a range of cancers. For example, researchers have identified compounds in green tea called catechins and others in black tea called theaflavins that both play roles in the death of breast cancer cells. Recent research done in China by Chinese and U.S. scientists, published in the journal Cancer Epidemiology Biomarkers & Prevention, looked at green tea and colorectal cancer in more than 69,000 women age 40 to 70. The researchers found that regular drinking of green tea correlated with a 37% reduction in the risk of getting cancer when compared with irregular tea consumption. And at this time of year, having some iced tea, either green or black, before you head outdoors may offer some protection against skin cancer. While scientists are investigating tea’s compounds for use in sunscreens, they’ve also found that drinking some may defend against skin tumours. But consider skipping the sugar-laden varieties, as their calories can certainly add up. Unsweetened, unadorned tea, on the other hand, is calorie-free.
If you would rather opt for tea supplements over the beverage, you might want to rethink your strategy. Many people interested in waist management know of the research linking green tea with elevated metabolic rates and increased calorie burning, but many supplements may not deliver the desired effect. For example, some of the weight-loss multivitamin formulations containing green tea compounds simply don’t contain enough to make any difference.
And then there are those green tea supplements that are too potent. In some cases, they may act as pro-oxidants and actually speed up oxidation, rather than slowing it down as the antioxidants in the beverage do. Researchers at Rutgers University have also reported cases of liver damage from high-dose supplements. While 10 cups of green tea a day isn’t harmful to the liver, supplements can contain the amount of polyphenols found in 50 cups. That’s not exactly moderation.
If you do opt for copious cups of green tea, keep in mind that the stimulant effect responsible for the increase in metabolic rates can also leave you wired or an insomniac, depending on the time of day you’re drinking. So be sure to monitor your own individual tolerance if you take up or increase your green tea consumption.
As the research on tea continues to percolate, you can bet that food companies will incorporate tea’s goodness into an assortment of food products. It’s already happening, with the arrival of yogourt containing green tea extracts and juice-tea combos. But as you explore these new items in the supermarket, check out whether they contain extracts of the real brew or simply a range of polyphenols that may not offer the same benefits. And remember, when it comes to extracts and supplements, you can get too much of a good thing.
-Rosie Schwartz is a Toronto-based consulting dietitian in private practice and author of The Enlightened Eater’s Whole Foods Guide: Harvest the Power of Phyto Foods (Viking Canada).
© National Post 2007