I recently received this really great request from Mercedes in Argentina:
“I find your blog really useful and attractive (and I have done a lot of previous research!). It would be wonderful to read your opinion about green and white tea and cancer prevention.”
First off, thank you Mercedes for your kind words! I am so happy to hear you have found this blog useful. Second, I love getting requests from readers! If you ever have a question or requests, send them to natalie AT breastcancerdefense DOT com. Alternately, you can find my contact info under the “contact” tab at the top of this webpage.
So let’s get to the good stuff… TEA!
A Brief Background on TEA
All tea comes from the same plant, Camellia Sinensis. There are five major categories of tea: white, green, oolong, black, and pu-erh. Herbal teas are actually classified as “tisanes” in the tea world.
White tea is the least processed of all the teas. The leaves are dried almost immediately after harvest, under careful conditions.
Green tea is cooked right after harvest, and then dried. Cooking immediately after harvest prevents any oxidation.
Oolong tea is partially oxidized, meaning the leaves are rattled around a bit in baskets to bruise the leaves and expose the juices to air for a precise amount of time. After this, they are cooked to stop further oxidation.
Black tea is completely oxidized, meaning it is left exposed to air longer than the oolong tea.
Pu-erh tea is fermented with microbes, which causes the tea to darken and change flavors. Like some wines, time increases the value of pu-erh tea.
What Makes Tea Healthy?
Tea contains healthy plant chemicals called polyphenols. There are different types of polyphenols. One groups is known as the catechins. This is the type studied for it’s anti-cancer potential. White and green teas have higher levels of catechins than black tea.
Tea preparation can affect the concentration of polyphenols. The highest concentration of polyphenols is found in brewed hot tea. Instant tea has less, and bottled tea is even lower. The decaffeination process also reduces polyphenol content.
Tea and Cancer Prevention – What Does the Research Say?
Argh! As with many other foods, there is not a definitive answer on tea and cancer prevention. There have been a lot of studies done in animals and test tubes that look very promising, but research in humans is not conclusive. Some human studies have shown a protective effect against cancer while others have not. It is yet to be determined whether or not tea has a direct effect on cancer prevention. The good news is that there really hasn’t been anything negative about tea consumption.
Here are some of the positive effects of tea consumption seen in research studies:
- High antioxidant activity which protects cells from DNA damage that could eventually lead to cancer.
- Stops spreading of cancer cells.
- Causes cancer cells to die.
- Stops the growth of new blood vessels, essentially “starving” the cancer.
- Protects against damage caused by UV light.
- Improves immune system function.
- Activates detoxification enzymes that may help protect against tumor development.
There have also been a number of studies looking at tea consumption in relation to breast cancer. In a review study from 2008 that I read, 8 out of 13 studies showed a protective effect of tea on breast cancer.
What about Caffeine?
You must keep in mind that tea has caffeine. Though the level of caffeine is much less than coffee, it is still present. Small amounts of caffeine are not harmful to consume on a daily basis. There is little evidence for any health risks for adults that consume 300-400 mg of caffeine each day.
Black tea contains the most caffeine at 64-112 mg per 8 oz, followed by oolong at 29-53 mg per 8 oz, then green at 24-39 mg per 8 oz, and lastly white tea at 32-37 mg per 8 oz.
If you feel let down by the fact that there is no clear answer about tea and cancer prevention, don’t be. I have long believed that no food or nutrient can single-handedly prevent cancer. It just doesn’t seem feasible. The way I look at it, tea is just another tool in your anti-cancer box.
What we do know is that tea contains some potent antioxidants, especially green and white tea. The more antioxidants you consume, the more equipped you will be to stave off cancer and other chronic disease. Plus, there is really nothing negative associated with tea drinking, except for maybe some stained teeth!
All the best,
photo by: Kanko on Flickr