Compared to people who drank less than one cup a day, seven or more cups of green tea a day may reduce the risk of dying from heart disease by a whopping 75 per cent, report scientists from Okayama University in the Annals of Epidemiology.
Additionally, a reduction in the risk of colorectal cancer mortality of 31 per cent was observed for people who drank more than seven cups of green a day, compared to people who frank less than three cups a day.
“To our knowledge, this is the first cohort study that shows the inverse association between green tea and colorectal cancer mortality,” wrote the researchers, led by Etsuji Suzuki.
The strong effects observed in the study may be due to long-term, high consumption of green tea, said the researchers. Only people aged between 65 and 84 participated in the study.
“Assuming that green tea consumption at the time of assessment is sufficiently representative of long-term, previous exposure to make a plausible link with the risk of mortality, the longer cumulative exposure to green tea may be responsible for the stronger effects of the present study, [compared to past studies],” they added.
The health profile of green tea are increasingly known to consumers, with studies reporting a wide range of effects, including a lower risk of certain cancers, improved heart health, weight loss, and protection against Alzheimer's.
Green tea contains between 30 and 40 per cent of water-extractable polyphenols, while black tea (green tea that has been oxidized by fermentation) contains between 3 and 10 per cent.
The four primary polyphenols found in fresh tealeaves are epigallocatechin gallate (EGCG), epigallocatechin (EGC) epicatechin gallate (ECG), and epicatechin (EC).
Study details
The Japanese team recruited 14,001 elderly residents in Japan, of which 12,251 individuals were analysed to estimate the various associations between green tea consumption and all-cause mortality, cancer and CVD.
During an average of 5.2 years of follow-up, 1,224 participants died, 400 were due to cancer, and 405 from cardiovascular disease (CVD).
Compared to people who drank less than one cup per day, drinking seven or more cups of green tea a day was associated with a 55 and 75 percent lower risk of all-cause and CVD mortality, respectively, said the researchers. Furthermore, “green tea consumption was associated with lower risk of colorectal cancer mortality”, they said. .
“The protective effects could have significant implications for public health,” they concluded.
Tea – the secret to eternal youth?
Recently, scientists from the Chinese University of Hong Kong reported that the cells of regular tea drinkers may have a younger biological age than cells from non-drinkers.
By looking at the length of telomeres, DNA sequences at the end of chromosomes that shorten as cells replicate and age, the Chinese researchers reported that the telomeres of people who drank an average of three cups of tea per day were about 4.6 kilobases longer than people who drank an average of a quarter of a cup a day.
This average difference in the telomere length corresponds to “approximately a difference of 5 years of life”, wrote the Hong Kong-based researchers.
Source: Annals of Epidemiology
Volume 19, Issue 10, Pages 732-739
“Green Tea Consumption and Mortality among Japanese Elderly People: The Prospective Shizuoka Elderly Cohort”
Authors: E. Suzuki, T. Yorifuji, S. Takao, H. Komatsu, M. Sugiyama, T. Ohta, K. Ishikawa-Takata, H. Doi