Tea has been used as a folk remedy for 5,000 years - to aid liver function, destroy typhoid germs, purify the body and preserve mental equilibrium - and now scientists are discovering it may have all those benefits and a whole lot more.
Studies presented at the Fourth International Scientific Symposium on Tea and Human Health, hosted by the US Department of Agriculture, this fall showed that tea can be key to a healthful diet.
"As a nutrition scientist, I consider tea as a healthy choice for three reasons: It meets hydration needs, it has no calories and it's really rich in phytonutrients [plant-based substances] that we know provide some human health benefits," said Jeffrey Blumberg, director of the Antioxidants Research Laboratory at Tufts University in Boston, in a telephone interview. "Tea has more of the catechins [a group of phytochemicals that act as antioxidants] than any food I am aware of. It is far and away the biggest, richest best source of those phytonutrients, and it's a pleasant, aromatic and flavorful beverage."
We asked Blumberg, co-chairman of the symposium, some questions about tea and health:
CP: Are green, black and Oolong teas equally healthy?
JB: I don't know of any controlled trials comparing the different colors of tea, but all of them come from the same plant, the Camellia sinensis bush, and there is a huge overlap in what we are finding in different studies using different kinds of tea. Most of the observational studies use green tea in Japan and China and black tea in the US, India and Great Britain, but they all show the same results. One study looked at models of digestion and found that in the gut, bacteria and enzymes break down different kinds of tea so that when it gets to human tissue, they are all pretty much the same.
CP: Do you get the same health benefits from taking tea supplements?
JB: There are not very many studies on tea supplements, yet the few that we have suggest they are mimicking some of the cardio and cancer benefits established in tea studies. You are going to get some of the same benefits from tea extracts, but they are not the same thing. I have a slight bias as a nutrition scientist. Mother Nature put a lot of different beneficial chemicals and compounds in tea so why not take advantage of all of them? By definition, supplements are 80 to 90 percent concentrated polyphenol extracts, primarily EGCG, a powerful antioxidant, but as far as I know, theanine amino acid is not in extracts, and theanine is what helps you to focus your attention or relax.
CP: How much do you need to drink to get the health benefits of tea?
JB: From lots and lots of observational studies, it looks like four to five cups a day will put you in the highest 20 percent for protection against heart disease and stroke. Those who drink four cups or more consistently have the lowest risk of heart disease. There is definitely a dose/response relationship, but most people don't drink eight or 10 or 20 cups a day, so I have no data on that.
CP: Can you drink too much tea?
JB: In animals, you can give absolutely mammoth amounts without harm, and in 5,000 years of human history there is no evidence of harm in healthy human beings, within a tremendous range (of doses). Tea is caffeinated - it has about half as much caffeine as coffee - so if you are caffeine-sensitive, you might want to drink decaf, but there is no evidence to suggest any adverse consequence from tea consumption, in an otherwise healthful diet. (However, one recent report showed that a woman who drank 2 gallons, or roughly 8 liters, of strong tea every day for two years developed calcium deposits in her bones, Blumberg noted.)