doses of epigallocatechin gallate (EGCG), an active ingredient in green tea,
was well tolerated, even at very high doses (up to 4000 mg/ day).
Furthermore, many also saw some degree of regression of their leukaemia.
Specifically, treatment with EGCG led to significant decreases in two key
CLL symptoms: high white blood cell (lymphocyte) counts; and enlarged lymph
nodes. Lymphocyte counts were reduced by 20 per cent or more in 11 of the 33
patients, while all but one of 12 patients with swollen lymph nodes saw a 50
per cent or greater reduction in swelling (J Clin Oncol, 2009; 27: 3808-14).
Although more research is needed to confirm these findings, this is not the
first study to suggest that green tea is a potent cancer fighter. Indeed,
the Feist-Weiller Cancer Center in Louisiana has reported that green tea
might be effective against prostate cancer.
Dr James Cardelli and his team gave 26 men with prostate cancer daily
supplements of a green-tea formulation (800 mg of EGCG plus other
polyphenols), equivalent to around 12 cups of normally brewed green tea.
After about a month, there was a significant decrease in a number of
biological disease markers such as prostate specific antigen (PSA) and
hepatocyte growth factor (HGF), which are indicators of cancer progression.
Some patients had reductions of more than 30 per cent, with no effects on
liver function (Cancer Prev Res [Phila Pa], 2009; 2: 673-82).
Green tea might also help to prevent cancer from developing in the first
place. People who drink lots of green tea are less likely to have certain
types of cancer than those who don't. Drinking five or more cups of green
tea every day reduces the risk of blood- and lymph-related cancers by about
50 per cent (Am J Epidemiol, 2009; 170: 730-8). In addition, a review of 51
studies of green tea concluded that green tea may help to protect against
cancers of the liver, lung, prostate, pancreas and colon (Cochrane Database
Syst Rev, 2009; 3: CD005004).
Green tea may also be useful for a host of other common ailments.
- Heart disease. Green tea can pre-vent atherosclerosis (narrowing of
the arteries) and stroke (J Am Coll Nutr, 2006; 25: 79-99; Complement Ther
Med, 2007; 15: 46-53), and lower blood pressure, cholesterol and the risk of
death due to heart disease (Prev Med, 1992; 21: 546-53).
- Osteoporosis. Green tea can prevent age-related bone loss, and
reduce fractures by increasing bone mineral density and support-ing
bone-forming activities (Nutr Res, 2009; 29: 437-56).
- Diabetes. A study of more than 17,000 adults found that green tea
was associated with a reduced risk of type 2 diabetes (Ann Intern Med, 2006;
- Obesity. Green tea is an effective tool for weight loss and
mainte-nance. In a randomized placebo-controlled study of nearly 200
moderately overweight people, two servings a day of high-catechin green tea
led to significant weight loss and, especially, abdominal fat (Obesity
[Silver Spring], 2009 Aug 13; Epub ahead of print).
- Tooth decay. Drinking green tea frequently throughout the day can
significantly reduce cavities, even in the presence of sugar in the diet. It
may also help to prevent periodontal (gum/bone) disease
(J Am Coll Nutr, 2006; 25: 79-99).
All teas (green, black and oolong) come from the same plant, Camellia
sinensis. However, as the production of green tea involves little
processing, these brews are rich in polyphenol catechins, the agents thought
to be responsible for much of green tea's beneficial effects. Green-tea
catechins, especially epigallocatechin gallate (EGCG), are potent
antioxidants-and antimutagenic, antidiabetic, anti-inflammatory,
antibacterial and antiviral, too (J Am Coll Nutr, 2006; 25: 79-99).
Precisely how much you need to drink to benefit is not known, but most of
the research is based on the amount of green tea typically consumed in Asian
countries-about 3 cups/day. Indeed, according to a recent review, a
desirable intake is 3-5 cups/day (up to 1200 mL/day) to provide a minimum of
250 mg/day of catechins (Cochrane Database Syst Rev, 2009; 3: CD005004).
Green tea is generally free of side-effects, although drinking large amounts
can lead to insomnia, anxiety and stomach upsets, due to its caffeine
content. Decaffeinated products are available but, as their catechin
content appears to be much reduced by the process (Nutr Cancer, 2003; 45:
226-35), you'd need to drink considerably more to get the same benefits as
from regular green tea.
Vol 20 07 October 2009