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The science of alcohol
The science of alcohol

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1.1 Units of alcohol

A unit of alcohol is a measure of the volume of pure alcohol contained in an alcoholic drink. In the UK, one unit of alcohol is equivalent to 10 ml of pure alcohol, regardless of what type of drink is involved. Table 1 gives some examples of drinks and the approximate number of UK units of alcohol they contain.

Table 1 Number of units of alcohol in common alcoholic drinks in the UK, where 1 unit equals 10 ml of pure alcohol.
A pint of ordinary strength lager (4% ABV)2 units
A pint of strong lager (5.5% ABV)3 units
A pint of ordinary bitter (4% ABV)2 units
A pint of best bitter (5.2% ABV)3 units
A pint of ordinary strength cider (5% ABV)2 units
A pint of strong cider (5.2% ABV)3 units
A 175 ml glass of red or white wine (12% ABV)~ 2 units
A pub measure (optic) of spirits (25 ml)1 unit
An alcopop ~ 1.5 units

In the early 1990s, the UK Government recommended that men should not drink more than 21 units per week while women should not drink more than 14 units per week.

However, after the initial guidance was provided, it quickly became apparent that many people were not distributing this consumption equally throughout the week and, as you have seen, this can be harmful. Therefore, more recent (2014) advice [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)] recommends a maximum number of units of alcohol per day. For men, this is 3–4 units of their weekly maximum of 21 units and, for women, this is 2–3 units of their maximum of 14 units per week.

In 2016, new guidance was issued by the Department of Health. The Chief Medical Officers' guideline for both men and women states that:

To keep health risks from alcohol to a low level it is safest not to drink more than 14 units a week on a regular basis

If you regularly drink as much as 14 units per week, it's best to spread your drinking evenly over three or more days. If you have one or two heavy drinking episodes a week, you increase your risk of long-term illness and injury.

Even with this guidance, it still remains a challenge for individuals to calculate the number of units they are drinking, even if they consider it a valuable exercise to keep track.

The Portman Group has a code of practice stating that a product must have the following labelling on it to promote responsibility:

  • unit alcohol content per container (and optionally per typical serving)
  • pregnancy logo and message – to alert drinkers to the dangers of drinking while pregnant
  • active signposting to the Drinkaware website.

The labelling used by the Cotswold Distillery on the reverse of their gin bottles is illustrated in Figure 3.

This is a photograph of a lavel from a gin bottle.
Figure 3 Product labelling to promote responsible drinking

Activity 2 Consumption awareness

Timing: Allow about 10 minutes

Watch the following video in which two different groups of students at an English university discuss their alcohol consumption including their understanding of UK units.

Download this video clip.Video player: sdk100_2015j_vid014-640x360.mp4
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Both groups of students can recall what they drink but very few had an awareness of how many units this equated to, with one student commenting that she did not know what a unit was. Estimations for the number of units in a bottle of wine varied from three to ten units, whereas it is actually eight to ten units in the UK. Some students also described alcohol in terms of percentage volume, rather than units. In most cases, what students reported drinking in one evening exceeded the recommended amounts.