Prevent stomach cancer by drinking green tea

Tea is great for you. Like coffee, tea (whether green or black) is a fantastic source of antioxidants, which help reduce your risk of many chronic diseases, from diabetes, to heart disease to cancer. In women, higher intake of black tea has been linked with reduced risk of ovarian cancer, specifically, while a study in China showed that drinking 5 or more cups of green tea per day reduced the risk of all-cause mortality by as much as 31%.

Another study in China showed that drinking green tea regularly for the long term (20 years or more) appeared to protect women from cancers of the digestive system, reducing their risk of any digestive system cancer (from esophageal cancer to colon cancer) by 28%.

Stomach (gastric) cancer is the fifth most common cancer in the world. A group of researchers based in China noted that over half of all cases worldwide occur in East Asia, with China being the largest source of cases. In light of the research regarding green tea and cancers of the digestive system, the authors sought to review published research regarding green tea and its effect, if any on stomach cancers (Pub Hlth Nutr 2017;20(17):3183-3192).

In their selection of studies to review they limited themselves to prospective cohort or case-control studies whose participants' ages were not restricted (including all adults; not just older or younger persons) in which brewed green tea was the factor being considered, and in which the number of cups per day - and for how many years that level of intake was sustained - were recorded, among other requirements. These criteria resulted in the inclusion of 13 different published studies, with the number of participants in the studies ranging from 400 to almost 200,000, the ages of participants ranging from 18 to 80, and the length of the studies lasting from just 5 months to as long as 19 years.

The authors were interested in knowing how much green tea an individual needed to drink for the beverage to have an effect on stomach cancer risk, so they looked at higher versus lower intakes of green tea. In the case-control studies they considered, lower amounts of green tea intake (up to 4 cups of green tea per day) showed little reduction in risk, while higher levels of intake - from 4-6 cups per day - reduced the risk of stomach cancer by 21%. Longer-term regular consumption of green tea also seemed to have an impact, with 25 years of regular green tea consumption reducing risk by 41%.

A particularly interesting outcome of their analysis came when they looked at the temperature of the tea the study participants consumed. While the data was not conclusive, the authors noted a tend toward higher risk of stomach cancers as the temperature of the tea increased, with regular consumption of warm tea having the lowest comparative risk and very hot tea increasing risk as much as ten-fold. Unfortunately the temperatures were reported in terms of "undrinkable, cool, warm, hot and very hot," not with exact temperatures, so what "very hot" might mean to one individual might not be the same "very hot" to another.

What this means for you

This study, while not conclusive by itself, still adds weight to the existing evidence that tea is not only great for you overall but may reduce your risk of digestive system cancers in general and stomach cancers in particular. Another reason to make coffee or brewed tea your non-water beverage of choice.

First posted: January 24, 2018