If you had been grown-up in the 1970s and the 1980s, you may remember what the buzz was then about the three caffeine-rich foods. Back in those days, tea, coffee, and chocolate were considered carcinogenic. It was not surprising then, that published reports of the time tended to support the popular belief. Much of the research done during the period carried the hypothesis that drinking tea had a harmful effect.

In the 1990s, there was a reversal in attitudes. Experimental research begun in the middle of the 1980s had started describing the antioxidant properties of tea. By the 1990s, research studies were driven by the hypothesis that tea had anti-carcinogenic properties. This direction of research is still being followed.

One of the relationships that researchers have tried to map out is that between tea and colorectal cancer. Perhaps before we take a look at what researches have to say about the relationship, let us first try to understand where colorectal cancer takes place.

The Colon

Everything you eat, from Apple pie to Zucchini, must be broken down into tiny particles and changed to simpler chemical substances that can be absorbed into the bloodstream. The complex process of digestion takes place in the 28ft (8m) long, twisting channel that starts at the mouth and ends at the anus.

When food reaches the colon — the last 6ft (2m) of the tract — most of the nourishment has been absorbed. In the colon, the major tasks are absorbing water, and some mineral salts, in the upper colon, then transporting and storing the indigestible remains of the food in the lower colon and the rectum, the last few inches connecting the colon to the anus. Cancer of the colon and the rectum is a common type of cancer.

Results of Research into the Relationship Between Tea and Colorectal Cancer

A compilation of epidemiological studies that examined the association between tea and colorectal cancer was made by a team of epidemiologists from the University of North Carolina and Wake Forest University. These were various studies conducted in Asia, Europe and the Americas, with research findings from a total of 12 countries derived from 30 publications.

In a number of studies, tea consumption appeared to prevent rectal cancer; and in six studies, particularly, there were indications of reduced risk among regular drinkers of tea. However, there were also several studies that showed higher risk among tea consumers and among high tea-consuming populations.

It was difficult, however, to gain some conclusive idea of the findings. There are many types of tea, and these differ in their ingredient profile. Aside from cultivar differences, ingredients also differ due to the extent to which enzymatic processes are allowed to continue: they may be cut short, to produce green tea, or allowed to run longer to form oolong and black teas.

Both green and black teas were covered in the studies, but there were geographic biases. Most studies on green tea were made in China and Japan, while the research on black tea was done in Europe, the Americas, and in Japan. Black tea is the major hot beverage used in the UK and Russia, and green tea in Japan and China. Iced black tea is more popular in the US (there is evidence that any preventive agents in tea are lost in the cold form of tea). There is also a relationship between coffee and colon cancer.

It may take some more time before conclusive evidence comes regarding the relationship of tea with colorectal cancer.