TEA – THE HEALTH BENEFITS


The following are extracts from a paper titled “The Role of Tea in Human Health: An Update”, presented at the Scientific Symposium on Health Benefits of Tea, held at Washington, D.C., in September 2002.


1. “The antioxidant capacity of teas and tea polyphenols has been assessed by several methods. Using the ORAC assay, found both green and black tea have much higher antioxidant activity against peroxyl radicals than vegetables such as garlic, kale, spinach and Brussels sprouts. Using TEAC assay, ranked epicatechin and catechin among the most potent of 24 plant-derived polyphenoic flavonoids they evaluated”

2. “Recently, several clinical trials have demonstrated that a single dose of tea improves plasma antioxidant capacity of health adults within 30 to 60 minutes of ingestion”

3. “In a trial of 40 male smokers in China and 27 men and women (smokers and non-smokers) in the U.S., oxidative DNA damage, lipid peroxidation and free radical generation were reduced after consuming 6 cups a day of green tea for 7 days”

4. “Ten patients with Type 2 diabetes consuming a high flavonoid diet for 2 weeks, including 6 cups a day of black tea, had a significant reduction in oxidative damage to lymphocyte DNA”

5. “…have observed an inverse association between flavonol intake and Cardiovascular Disease in Europe, where black tea…contributes substantially to total flavonol consumption”

6. “Epidemiological evidence, particularly from a 10 to 15 year follow up of …550-800 men from the…study in Netherlands, reveals a strong inverse association between flavonol intake and Coronary Heart Disease mortality and stroke incidence. Similarly, men and women from the Boston Area Health Study, who consumed one or more cups a day of tea in the previous year, had a 44% lower risk of myocardial infarction than those who drank no tea”

7. Tea consumption has been inversely associated with the development and progression of atherosclerosis…determined atherosclerosis by coronary arteriography in 512 Japanese patients over 30 years of age and reported a protective effect of tea among those not being treated for diabetes”

8. “Evidence for the anticarcinogenic potential of tea polyphenols has been provided by numerous in vitro and experimental studies. Some epidemiological studies also support a protective role of tea against the development of cancer”

9. A Japanese study of 472 stage I and stage II breast cancer patients found an inverse correlation between the consumption of green tea and the rate of recurrence after 7 years

10. “…reported that consumption of 2 or more cups of black tea daily reduced the risk of lung cancer by 66% in a case control study of 855 male smokers in Uruguay”

11. “…a significant reduction in risk of stomach cancer was found in a population-based case-control study among 944 Polish women who drank tea daily…It is noteworthy that black tea theaflavins can induce apoptosis and inhibit the growth of human stomach cancer cells in a time and dose dependent manner. Several studies in Japan and china have shown a protective effect of green tea on stomach cancer, with the greatest effect among those with the highest levels of consumption”

12. “Several experimental studies indicate a strong chemopreventive action of tea flavonoids against cancers of the gastrointestinal tract, particularly colorectal cancers”

13. “A case-control study of 882 Japanese by…indicated a protective effect of green tea on bladder cancer, particularly among women…in a follow up study…found patients who drank green tea had a substantially better 5 year survival rate than those who did not…a population-based case-control study of 4000 Americans indicated intake of more than 5 cups of tea a day was associated with a 30% reduction in risk of bladder cancer…”

14. “Drinking tea was associated with lower levels of dental caries in a cross-sectional study of 6014 school children in England…because of its natural fluoride. In addition, extracts of green tea inhibit oral bacteria such as…Oolong tea polyphenols appear to inhibit bacterial adherence to tooth surfaces…”

15. “Tea consumption was identified as an independent factor protecting against the risk of hip fractures in (?) women and 7 men over age 50…Consistent with the observation…studied 1256 British women, 65 to 76 years of age, and found that those who drank tea had greater bone mineral density than those who did not…”

16. “In a randomized clinical trial controlling for caffeine intake,…, a green tea extract containing 90mg EGCG increased the energy expenditure and decreased the respiratory quotient of 10 healthy young men 24 hours after consumption. Urinary nitrogen was not affected but 24 hour urinary norepinephrine excretion increased by 40% during treatment. The investigators of this study suggest a potential role of tea in the control of bodyweight”

17. “While not determining tea intake per se,…found the 2 highest…of flavonoid intake among 1367 subjects older than 65 was associated with a significant reduction in the risk of dementia…reported that day-long consumption of tea improved the cognitive and psychomotor performance of healthy adults…”

18. “…In an examination of the prospective Nurses’ Health Study, a cohort of more than 81000 women, 40 to 65 years of age,…found an inverse association between tea consumption and the risk of kidney stone formation. Employing a multivariate model that adjust (sic) simultaneously for 17 beverages and other potential risk factors, each 240ml serving of tea
consumed daily decreased the risk of developing kidney stones by 8%”