An interesting news article

Tea drinkers who get their news online may have already seen this recent article, which describes a scientific study that linked regular steaming hot tea drinking with an increase of esophageal cancer. The study took place in Iran, where black tea drinking is widespread in its popularity. Interestingly, the study found that drinking tea at 'steaming hot' temperature (between 149º and 159º F) doubles the risk of cancer, and drinking tea at temperatures above 159º F increases the risk eightfold!

Of course, once I read this, I broke out the thermometer and quickly started experimenting with drinking water at different temperatures. Personally, I find that the temperature at which I like to drink tea is generally below 150º; I tried 160º water and, not surprisingly (I don't have an especially high tolerance for hot drinks) it was a little too hot for my tastes. The study also notes that most cultures that prefer to add milk to their tea don't have an especially high instance of esophageal cancer, most likely because the milk cools the tea to a lower temperature. Of course, this is only one study, so we should probably wait for more evidence before taking it as scientific law, but it does raise a few interesting points.

I think it's a good reminder that, ideally, tea can be an opportunity to relax and make a concentrated effort to take a short break in the day to sit and enjoy the intricacies of a delicious beverage--waiting a couple of extra minutes for your tea to cool can be an opportunity to get your thoughts together and focus on what you need to get done for the day, or it could just be a chance to anticipate the tea you're about to experience. I know some people feel like "the hotter the better," but I find that a really complex tea's flavor is usually much easier to appreciate if it's had a chance to cool down a little. Finally, I think this study exhibits one of the most difficult aspects of scientific tea studies--the tea drinkers in the study all consumed black tea. It seems to me that with the effects that different processing techniques have on the composition of tea leaves, combined with the different methods used to prepare the teas, it must be a bit difficult to generalize anything about tea without meticulously including all different tea types in a study. That is to say, for example, does drinking steaming hot oolong affect cancer risk in the same way? Studies that focus on the health benefits of tea have returned some pretty solid evidence that the different tea types at least have different strengths when it comes to health benefits, so I think it stands to reason that they might show slight physiological differences in other studies. Reading tea studies is always exciting, since each study is another link in a growing chain of evidence that helps us make more confident claims about how tea affects the human body. Unfortunately, because of the variables involved, tea is such a complicated, multifaceted subject that it will probably be quite a while before we've mastered it as a subject.



Jane@Los Angeles Asian Furniture said...

I just stumbled here and want to give you a delayed thank you for writing this blog. My husband often teases me for waiting for my tea to cool a bit before drinking it. Now I have something to back it up. I will look up your store next time I'm in Seattle.

bruce said...

On 02/20/10 12:55 AM, Bruce C. Mitchell wrote:

New Evidence That Green Tea May Help Fight Glaucoma and Other Eye Diseases
ScienceDaily (Feb. 20, 2010) — Scientists have confirmed that the healthful substances found in green tea -- renowned for their powerful antioxidant and disease-fighting properties -- do penetrate into tissues of the eye. Their new report, the first documenting how the lens, retina, and other eye tissues absorb these substances, raises the possibility that green tea may protect against glaucoma and other common eye diseases.

It appears in the Journal of Agricultural and Food Chemistry.

Chi Pui Pang and colleagues point out that so-called green tea "catechins" have been among a number of antioxidants thought capable of protecting the eye. Those include vitamin C, vitamin E, lutein, and zeaxanthin. Until now, however, nobody knew if the catechins in green tea actually passed from the stomach and gastrointestinal tract into the tissues of the eye.

Pang and his colleagues resolved that uncertainty in experiments with laboratory rats that drank green tea. Analysis of eye tissues showed beyond a doubt that eye structures absorbed significant amounts of individual catechins. The retina, for example, absorbed the highest levels of gallocatechin, while the aqueous humor tended to absorb epigallocatechin. The effects of green tea catechins in reducing harmful oxidative stress in the eye lasted for up to 20 hours. "Our results indicate that green tea consumption could benefit the eye against oxidative stress," the report concludes.

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