Men who drank four cups of coffee or more daily were almost twice as likely to get bladder cancer as members of a control group who did not drink coffee, according to results published in the journal Chronic Diseases in Canada.
"The attributable risk estimates indicated 33 per cent of bladder cancers among men could have been prevented by elimination of coffee consumption," report the scientists led by Anne-Marie Ugnat.
Bladder cancer is the fourth most common cancer in Canadian men and it has been estimated that 3,700 cases will be diagnosed this year.
The main purpose of the study was to examine risks of bladder cancer associated with industrial chemicals, but smoking and coffee were included because both have been flagged as risk factors in previous studies.
The risk associated with heavy coffee drinking was found to be greater than for workplace exposure to asbestos or lubricating oil, but not as great as for smoking or exposure to benzidine, a chemical used in the petrochemical industry.
"We . . . confirmed that smoking and coffee consumption were significantly related to increased bladder cancer risk," claims the study.
The proportion of bladder cancer attributable to smoking and heavy coffee consumption were 51 per cent and 17 per cent respectively, add the researchers.
The Health Canada study was based on 549 men with bladder cancer and 1,099 men in a control group. It was confined to the four Western provinces because data was not available from Ontario, Quebec or New Brunswick.
Risk of bladder cancer was found to be 3.32 times greater among heavy smokers than among members of the control group and 1.77 times greater among heavy coffee drinkers.
A report in Canada Press quotes Ronald Moore, professor of oncology at the University of Alberta, as discounting the coffee-cancer link, saying the most recent analyses of the scientific literature show no relationship. But he conceded the question is difficult because of numerous compounding factors.
"Do people that drink coffee smoke more? Probably the most important things that come into play are the occupational factors and unless you can really sort out those things . . . you'd never be able to prove (a link)."
These latest findings from Canada will do little to comfort a coffee industry dogged by 100 year price lows. According to the intergovernmental, UN-backed International Coffee Organisation, although the coffee business is booming in consuming developed countries, current rock bottom prices are causing immense hardship to countries where coffee is a key economic activity, as well as to the farmers who produce it.
In the early 1990s earnings by coffee producing countries reached $10-12 billion and the value of retail sales of coffee, largely in industrialised countries, about $30 billion. Now the value of retail sales exceeds $70 billion but coffee producing countries only receive US$5.5 billion.
Prices on world markets, which averaged around 120 US cents/lb in the 1980s, are now around 50 cents, the lowest in real terms for 100 years.
Although consumers could be expected to benefit from low prices this is not the case in coffee. Firstly, the amount accruing to the farmer from the retail sales price of a cup of coffee in a coffee shop is probably less than 2 per cent and secondly, excessively low prices lead to lower quality, writes the ICO.
Value-added crops could help ease the industry out of the economic crisis. A key example: in June this year researchers at the State University of Campinas in Brazil discovered the decaffeinated version of Coffea arabica, the most cultivated and consumed coffee in the world. There are hopes that this could lead to cheap alternatives to artificially decaffeinated coffee on the market today.