Tea 'could help prevent cancer'

A cup of tea could help prevent cancer

Drinking tea could help prevent cancers, say scientists.

They say antioxidants in tea offer protective benefits against cancers of the stomach and oesophagus (gullet).

A study in China showed tea drinkers were around half as likely to develop the cancers as others who did not drink tea.

The researchers looked to see whether certain chemicals called polyphenols, which are present in tea, were present in the urine of the men they studied.

The protective effect of tea is far from proven, and more well-designed, large-scale human studies are needed

Thomas Lober, Cancer Research UK

The presence of the chemicals was associated with a lower cancer risk, leading the US researchers to conclude they had cancer-preventing properties.

Tea comes from the plant, Camellia sinensis, which is thought to contain extremely powerful antioxidants.

Antioxidants are important because they combat the body's free radicals - charged particles, produced by the body, which can damage cells.

It is thought that under a state of imbalance, or oxidative stress, cells may mutate and contribute to disease processes, including cancer.

Tea contains antioxidants - polyphenols called catechins - that have been shown to be as powerful as the well-established antioxidants vitamins C and E at protecting proteins and DNA from oxidative damage.

Green tea contains the most catechins, followed by oolong and black teas.

Other studies have shown catechins can halt tumour cell growth and protect healthy cells from damage.

Lower risk

The team from the Keck School of Medicine of the University of Southern California, Rutgers University and Shanghai Cancer Institute began their research in 1986.

They followed 18,244 men aged 45 to 64 in Shanghai.

They discovered 190 cases of stomach cancer and 42 cases of oesophageal cancer.

They compared them with 772 similar men without cancer.

They checked for polyphenols and for chemicals produced when polyphenols break down in the body.

Polyphenols included epigallocatechin (EGC) and epicatechin (EC).

The presence of EGC in urine was associated with a lower risk of gastric and oesophageal cancer, even after adjusting for smoking and alcohol drinking.

The researchers also adjusted for levels of carotenes, natural chemicals found in carrots, spinach and other vegetables and fruit thought to reduce the risk of cancer and other diseases, and H. pylori, a type of bacteria linked to peptic ulcers.

Researchers observed cancer-protective effects mostly in people who had lower-than-average levels of carotenes in their blood.

'Anti-cancer effects'

Mimi Yu, professor of preventive medicine at the Keck School of Medicine, said: "This study provides direct evidence that tea polyphenols may act as chemopreventive agents against gastric and 0esophageal cancer development."

But Thomas Lober, of Cancer Research UK, told BBC News Online: "Green and black teas have both shown promising anti-cancer effects in lab studies, and tea-drinking may be associated with a lower risk of some human cancers.

"But the protective effect of tea is far from proven, and more well-designed, large-scale human studies are needed."

Bill Gorman, executive director of The Tea Council, said: "The findings from this study further add to the growing evidence demonstrating tea's potential role in reducing the risk of certain cancers.

"It is good to see more human studies providing a direct link with tea polyphenols and positive health benefits.

"The conclusions from these types of studies highlights yet another good reason for drinking tea."

Results of the ongoing study were presented to the annual meeting of the American Association for Cancer Research.