1. Facts about Alcohol Content of Drinks
The Unit System
The alcohol content of the various alcoholic beverages differs widely. Thus similar quantities of the various beverages can contain markedly different quantities of alcohol. The alcohol content of a given beverage is, however, easily calculated from its percentage alcohol content by volume (% ABV), which is clearly marked on the container, taking the specific gravity of alcohol into account, viz.
The absolute amount of alcohol in a given drink can then be calculated by reference to its volume (Table 1.1).
In order to simplify the quantification and hence to facilitate assessment of alcohol intake, a system, based on defining quantities of beverages containing equivalent amounts of alcohol has been devised for use in Great Britain. A 'unit' of alcohol is the amount contained in 1/2 pint (284 ml) of beer, a single glass (125 ml) of table wine, a single glass (50 ml) of fortified wine, for example sherry, or a single measure (25 ml) of spirits; it approximates to 10 ml or 8 g of absolute alcohol.
Inaccuracies of the Unit System
This system is now used widely by the lay public, by 'alcohol agencies' and by physicians alike. As currently publicized, however, it is greatly over-simplified.
The accuracy of the 'unit' system can be improved by taking differences in beverage strengths and volumes into account. Thus, the exact number of units of alcohol in a given beverage volume can be calculated from the % ABV using the information that 10 ml of absolute alcohol is equivalent to 1 unit of alcohol. Thus the number of units of alcohol in a given volume of beverage equals:
A half-litre can of 8% ABV lager contains 4 units of alcohol ; likewise, a 750 ml bottle of 13% ABV wine contains 9.8 units of alcohol (Table 1.3).
In recent years new ranges of fortified wines, such as MD 20/20 and Mad Dog, strong white ciders, such as Diamond White and Ice Dragon, fruit-flavoured lagers and ciders, such as Desperados and Maxblack and alcoholized soft drinks, the co-called 'Alcopops', such as Hooch alcoholic lemon, have been marketed. The fortified wines have sweet fruit flavours such as cherry, banana and strawberry and a % ABV of between 13 and 21%. The white ciders, which are filtered to remove colour and some flavours, have a % ABV of between 8 and 9%. The lagers and ciders which are additionally flavoured with citrus fruits or blackcurrant and the 'Alcopops' which are essentially soft drinks which have been 'fortified' with alcohol have a % ABV of between 5 to 6%. These drinks are attractively packaged, often in small volumes, which may nevertheless contain several units of alcohol. Their obvious appeal to young people has become a focus of public concern.
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