Green tea cancer benefit a myth

BOSTON - For years, green tea has been promoted for its ability to prevent stomach cancer - the second leading cause of cancer deaths. But a new study suggests its reputation is undeserved.

Doctors in Japan and Massachusetts say their analysis of 419 cases of stomach cancer among northern Japanese shows the risk of developing a stomach tumour is not related to the amount of green tea drunk.

"Those who enjoy green tea as a beverage can continue to drink it, but there should be no expectation that this practice will reduce the risk of gastric cancer," Dr Takeshi Sano and Dr Mitsuru Sasako, of Tokyo's National Cancer Centre Hospital, wrote in the New England Journal of Medicine.

Until now, there were plenty of reasons to think that green tea had anti-cancer properties.

Test-tube studies showed that green-tea extract slowed the cancer process and also caused cancer cells to self-destruct. In tests on animals, the extract seemed to prevent tumours from developing.

Researchers tried to reconstruct the tea-drinking habits of people with and without stomach cancer.

Four studies found that tea drinkers were less likely to develop stomach cancer than those who did not drink tea but three studies showed no benefits. The studies were only as reliable as the ability of the volunteers to recall how much tea they drank over many years.

The latest study, led by Dr Yoshitaka Tsubono of the Tohoku University Graduate School of Medicine in Sendai, overcame the recall problem by distributing questionnaires in 1984 to 26,311 people in northern Japan.

The rate of stomach cancer in northern Japan is high and the popularity of green tea varies widely.

Over the next nine years, the Tsubono team identified 419 people with stomach cancer in that group.

They were no less likely to drink green tea than people without cancer. The researchers also found no link between stomach cancer and the consumption of coffee or black tea.

Researchers gave another reason for why earlier studies might have found higher rates of cancer among people who did not drink green tea.

They said people with abdominal symptoms caused by undiagnosed stomach cancer might have cut back their green-tea drinking years before their cancer was diagnosed.

Stomach cancer kills 49,000 Japanese each year, making it responsible for 18 per cent of all cancer-related deaths.

The rate is eight times lower in the United States.

- REUTERS