Drinking green tea and not smoking could add over a decade to your life. (Photo by Kanko*)
Since green tea has such a wide range of health benefits, it is commonly assumed that drinking green tea slows down aging in general. However, epidemiological proof of tea extending lifespan is lacking for the most part.
Now it seems that this hypothesis has indeed been proven true. Nakachi et al. followed the green tea consumption and deaths (cancer, cardiovascular death and all cause mortality) in a Japanese population for 13 years. Since the Japanese have one of the longest life expectancies in the world, they're ideal for a study like this.
Green tea and cancer
The authors found that onset of cancer and death from cancer were significantly delayed in those who drank the most green tea. That is, they developed cancer later and died from cancer later than those who drank less tea. Compared to people who drank three cups or less per day, those who consumed at least 10 cups had a 41% less chance of getting cancer.
The cancer-preventative effect was more pronounced in women than men: mean age at cancer onset in women who drank more than 10 cups was 7.6 years later than in those who drank less than three cups, whereas in men the delay was 4.1 years. The difference in age at cancer death was 3.9 years and 5.9 years in men and women, respectively.
The figure above shows the age-specific cancer death rates among women by daily consumption of green tea. You can see that up until the age of 80, higher green tea consumption correlates with less cancer rather clearly, but after that the data gets mixed.
Green tea and cardiovascular deaths
Cardiovascular deaths were similarly inversely correlated with green tea consumption in both men and women.
In men, mean age at cardiovascular death was 74.9 years in those who drank up to 3 cups, 76.2 years in those who drank 4-9 cups, and 76.8 years in those who drank more than 10 cups. In women, the values were 79.5 years, 80.6 years, and 80.9 years. Even though the women lived longer, here the effect of green tea on lifespan was more pronounced in men.
Green tea and all cause death
Mean age at death among men and women drinking more than 10 cups per day was 4.3 and 3.8 years higher, respectively, than those consuming less than three cups.
The largest difference in age of death was observed between smokers who drank less than 3 cups and non-smokers who drank more than 10 cups: mean ages of death were 67.7 and 79.4 years, respectively. So drinking lots of green tea and not smoking extended lifespan by more than ten years.
The figure above shows the cumulative survival among women over 40 by daily consumption of green tea. Again, those who drank more had a better chance of surviving onto the next year: 74% of those who drank up to three cups, 80% of those who drank 4-9 cups, and 82% of those who drank more than 10 cups were alive at age 80. After that, the differences became smaller.
The authors conclude:
The median survival time (equivalent to average lifespan of women who have already lived to the age of 40) was 87.1, 88.2 or 89.9 years for groups consuming below 3 cups, 4-9 cups, and over 10 cups a day, respectively, indicating about two years longer lifetime associated with large consumption of green tea.
On the other hand, cumulative survival among men did not show such clear differences by consumption of green tea as were seen in women. This is in part due to the deleterious effect of cigarette smoking, which apparently disturbs the beneficial effects of green tea. In fact, when we divided men by smoking status, the life-table analysis among non-smokers showed [that] current smokers consuming over 10 cups a day showed the highest survival in ages before 70, and there were no substantial differences in cumulative survival in ages after 70 between the group consuming over 10 cups and 4-9 cups a day, although smokers consuming below three cups had a much lower survival.
Green tea increases lifespan by preventing death from age-related illnesses, especially cancer. The cancer-protective effect of green tea is especially pronounced in women, whereas the protection from cardiovascular death seems to be stronger in men.
Mean age at death from all causes was ~4 years higher in those who drank more than 10 cups than those who drank less than three cups per day. The best combination was more than 10 cups of green tea and no smoking, whereas the worst combination was less than three cups of green tea plus smoking. The difference in age of death between these two groups was almost 12 years.
If you're after those extra years, you should start drinking green tea during middle age or earlier. And even though more may not always be better, in this case it seems to be: if you can handle 10 cups per day like some of the Japanese in this study did, go for it.
For more information on green tea, see these posts:
Green Tea, Black Tea & Oolong Tea Increase Insulin Activity by More than 1500%
Green Tea Grows Hair in Vitro, Might Work in Vivo
Green Tea Reduces the Formation of AGEs
Dental Health Effects of Green and Black Tea