Clear labelling on shop-bought alcohol, showing the alcohol units contained and health advice, may not be effective in promoting sensible drinking, says a letter in this week’s BMJ.

In a snapshot survey of 263 supermarket shoppers in Edinburgh, two university lecturers investigated whether information labels on alcoholic drinks influenced drinking awareness.

Although most of those surveyed could define what constitutes a unit of alcohol, less than a fifth of men and just a quarter of women used the information to monitor how much they drank.

Very few - just 8% of women and 5% of men - were aware of the current guidelines which outline sensible daily drinking levels (brought in to help people avoid drunkenness). Many instead estimated the maximum number of units per day from older guidelines defining weekly levels, while a third offered no suggestion at all.

Nearly half of the shoppers surveyed preferred wine, but a fifth of those gave no estimate on how many units are in a bottle. Another third thought the alcohol content to be less than it is - guessing seven units or fewer, when the right answer is closer to nine.

Most participants said they were in favour of alcohol labelling. However, the survey found price offers influenced buying more than label information.

Despite the enthusiasm for labelling amongst the participants, evidence from other countries on its effectiveness is not supportive, say the authors. This survey shows there may be “considerable confusion about sensible drinking messages in the UK,” they conclude.