Julia Hinde reports from the annual American Association for the Advancement of Science meeting in Seattle

If coffee was our worst vice, we would be in fine shape, says a leading medical academic from Seattle, America's coffee capital.

Addressing the AAAS meeting this week, John Potter, of the Fred Hutchinson Cancer Research Center and the University of Washington, said moderate coffee drinkers worried about cancer scares could sleep easy at night - providing, that is, they had not drunk too much of the stimulant and were too wired to rest.

"There appears to be only a very weak connection, where people who drink vast quantities may be at higher risk," he said.

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"Most of us think there are much more important causes of cancer such as smoking."

Coffee may be a factor in increased risk of bladder cancer he said, particularly among people who drink more than seven cups a day and smoke too.

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But there was less strong evidence of a link between coffee consumption and pancreas cancer.

British-born Professor Potter, who admits to drinking just one cup of coffee a day, put aside his work evaluating the health benefits of fruit and vegetables to turn his attention to the national drink for the purposes of the conference.