Underestimates of consumption are possible

EDITOR—Hart et al say that the mortality curve in relation to alcohol consumption may not be U shaped or J shaped once socioeconomic and confounding factors are taken into account.1 We should like to raise concerns about the estimates of weekly alcohol consumption used, in particular by taking one bottle of wine to be equivalent to six units of alcohol. This value is only true for a 750 ml bottle of wine that is 8% alcohol by volume. Apart from some German wines, most wines are between 11% and 13.5% alcohol by volume. Many supermarket wines now state how many units of alcohol are contained in each 125 ml glass.

Our brief survey in a large supermarket to assess their alcohol contents of a random selection of wines (table) shows that the actual number of units consumed in wine could be underestimated by as much as 37.5% per bottle for some types of wine, counting only 6 units of the possible 9.6 units consumed. This would have the effect of placing individuals in lower intake groups than they perhaps ought to be, and attributing to these groups health effects that are actually related to …