Coffee might dampen cancerous damage from smoking

2000-12-13 12:37

London - Drinking coffee regularly might protect smokers from bladder cancer, a new study suggests.

The preliminary research, published this week in the London-based Journal of Epidemiology and Community Health, found that bladder cancer was about half as likely to occur in smokers who regularly drank coffee as in smokers who did not.

"This could suggest that the coffee consumption modifies the effect of tobacco smoking," said Dr. Gonzalo Lopez-Abente of the Carlos III Health Institute in Madrid, Spain, who led the study.

Experts not connected with the research had mixed reactions to the main finding, ranging from the view that it highlights the often-unexpected protective effects of substance found in food to the opinion that the theory is fatally flawed by the study's methodology.

All of them agreed, however, that the best way to reduce the chances of getting bladder cancer is to stop smoking.

In the study, smokers who drank coffee still had triple the chance of developing the disease as non-smokers who drank coffee. But smokers who didn't drink coffee were seven times as likely to get the disease as non-smokers who did not drink it.

"Our suspicion about this possible difference (between those who do and don't drink coffee) arose some years ago when we had observed that there could be a little increase of bladder cancer risk for coffee drinking, but this risk was only observable in non-smokers," Lopez-Abente said.

Smoking is recognised as the most important cause of bladder cancer. Experts estimate that about 50 percent of these cancers in men and 30 percent in women are due to smoking.

Cigarette use increases the risk for bladder cancer by two to five times and, when smokers quit, their risk declines in two to four years, according to the US National Cancer Institute.

Some preliminary research in the 1980s linked caffeine with an increased chance of getting bladder cancer, but the link didn't pan out on closer investigation.

The Spanish study involved 497 people with bladder cancer, who were compared with 1 100 people without the disease. They were all asked about their smoking and coffee-drinking habits. Those who drank less than two cups of coffee a week were classified as non-coffee drinkers.

"The mechanisms suggested for the apparent protective effects of coffee are quite plausible," said Ian Johnson, head of intestinal physiology and cellular metabolism at the Institute of Food Research.

"But it is worth noting that substances found in vegetables like broccoli and Brussels sprouts exert similar biochemical effects, and may be even more protective against tobacco-related cancers," Johnson said.

Dr Robert Huddart, a cancer expert at the Royal Marsden Hospital and the Institute of Cancer Research in London said the study raises an interesting hypothesis that needs to be tested by other scientists before real confidence can be placed in it.

Dr Annie Sasco, chief of epidemiology for cancer prevention at the International Agency for Research on Cancer, part of the World Health Organisation, was less impressed.

"It sounds a little bizarre," Sasco said. "There is nothing about potential other sources of caffeine, such as tea and Coca-Cola, and it's very strange to categorise people who drink two cups of coffee a week as non-coffee drinkers."

"I don't find it very convincing at all," she said. - Sapa-AP

- SAPA