Drinking can damage your liver, as we've all known for a long time. But how many moderate drinkers end up in NHS liver-wards?

Professor Ian Gilmore, President of the Royal College of Physicians and a fierce opponent of drink, wrote to The Times arguing that the numbers are so high that one can conclude that even the moderate drinkers of "Middle England" are taking more than is good for them.

It's a false conclusion to draw from this evidence, responded Professor David Hand, President of the Royal Statistical Society, in a letter in The Times today. He says: "The premise shows that if one is a liver-ward patient then the probability of being a daily or frequent drinker is very high. But it says little directly about the probability of being on a liver-ward if one is a daily or frequent drinker - which is surely what one is interested in.

"This mistake has arisen sufficiently often for it to be given a name: the error of the transposed conditional."

Meanwhile, the latest results from the long-running Zutphen study in the Netherlands should encourage at least the occasional tipple. A 40-year follow-up of 1,373 men concludes that "light" wine consumption was associated with five years longer life expectancy at the age of 50, compared with non-drinkers. Those who drank beer or spirits also benefitted, but only by about two years, not five.

It's possible, of course, that healthier people drink, rather than drinking people being healthier. Correlation is not causation. But Dr Marinette Streppel and colleagues from Wageningen University say that the same effect was found in all socioeconomic groups. Mind you, it's hardly a licence to get plastered: the average consumption in the long-lived Dutchmen was only about half a glass of red wine a day.

Source: The Times, April 27 and April 30; Journal of Epidemiology and Community Health online