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Monday, October 27, 2014 - 16:02
Beware the misleading unit

It is often stated that a unit of alcohol is supplied by a small glass of wine, half a pint of beer, or a single measure of spirits. Such statements can be misleading because they do not reflect differences in strength of the various kinds of wines, beers, and spirits. There’s no question that alcoholic consumption of even the smallest amount can impair physical mobility, reaction time, thought process and mental alertness. But while many authorities warn drivers, for example, against drinking more than two units of alcohol, this is an unhelpful guideline. Just two units of alcohol (two whiskies, say) may be sufficiently debilitating to suggest a person should not drive, yet many believe it would be safe to do so because of the almost universal guideline that you are ‘over the limit’ only if you have had more than two glasses of alcoholic drink.

The thing is ‘units of alcohol’ and size of glass, and type of liquor can all affect the resultant BAC (blood alcohol content). I have tried to determine roughly the value of units of alcohol for a given drink. I think most people will be surprised. Note that you can do your own calculation, if you have a mind to, by using the formula detailed later on.

Beer. The quantity of one unit of beer with an alcohol by volume (ABV) of 3.5% is 284 ml. That is less than a small bottle of beer! Even so, most beers are stronger. In South Africa beers generally range from 4.5% – 5.5% ABV. This means, for example, that a typical single lager of around 5.5% alcohol would contain almost two units of alcohol, not one; in fact, 568ml of lager at 5.2% alcohol contains almost 3 units of alcohol. Stronger beer (6%-12%) may contain as much as 2 units per 300ml. To revert to rounded figures in litres, for example:
A half litre of standard 5% lager contains 2.5 units;
One litre of German brewed beer (5.5%–6%) contains 5.5 – 6 units of alcohol.
Wines. A medium glass (175 ml) of 12% alcohol wine contains around two units of alcohol, not one. A large glass (250 ml) would contain three units. Red wine may have a higher alcohol content (on average 14%, sometimes up to 16%). A 750 ml bottle of wine (12% alcohol) contains 9 units. A 750 ml bottle of 14.5% wine contains 10.88 units. So if you share a bottle of wine with a partner at dinner, aside from any pre-dinner drinks or anything else, you have already both had five units of alcohol. More than two units and, technically you are over the limit. Pretty bleak if you drove to the restaurant – and I bet you did
Fortified wines. A small glass (50 ml) of sherry, fortified wine, port, or cream liqueur (20% alcohol) contains about one unit. A bottle would amount to 15 units of alcohol.
Spirits. Most spirits, such as whisky, rum or vodka, for example, have 40%-43% alcohol content. So a single measure (25 ml) of a spirit contains one unit. But who doesn’t ask for a “double”?
Alcopops. Most alcopops contain 1.4 – 1.5 units per regular 275ml bottle. As an example, a Bacardi Breezer or a Smirnoff Ice, both contain 1.5 units of alcohol.

Health issues. For health reasons, most authorities advise against drinking more than the regular daily dose of 3-4 units of alcohol for men (equivalent to a pint and a half of 4% beer) and 2-3 units of alcohol for women (remember, two units is equivalent to a single 175 ml glass of wine). ‘Regular’ means drinking every day or most days of the week.
Various countries define a ‘unit of alcohol’ differently. In the UK, for example, a unit of alcohol is defined as 8 grams (10ml); while in Australia as 10 grams (which would be 12.7 ml). In South Africa we rate a unit as 12 grams of pure alcohol. The World Health Organisation, incidentally, has settled on 10 grams as being a unit of alcohol.

Metabolism. Assuming the WHO standard, the body can metabolise one unit of alcohol in a little over 45 minutes (10ml). The rate is fixed. So no matter the gender, the body weight, the level of physical activity the body will metabolise at that fixed rate of about 13ml per hour. Of course, most drinks contain more than one unit of alcohol, which is where the general guideline that the body can metabolise one drink an hour comes in. And it is a better, easier way to think of it.

Technically speaking the liver gets the arduous task of metabolising most of the alcohol, of which around 92% of that consumed arrives there (but up to 98% under certain circumstances), because the other 8% is discharged through sweat, urination and breathing. The liver converts the alcohol to acetaldehyde using enzymes (the brain evidently has an enzyme that can metabolise a little bit of the alcohol). Since this is a poison the body must get rid of it before the liver can metabolise any more of the alcohol — which is why the metabolic rate is a controlled steady fixed rate for all people. Acetaldehyde is an organic chemical compound. It is a colourless liquid with a pungent, fruity odour. It is toxic, highly flammable and is a dangerous fire and explosion risk. It is used in the manufacture of acetic acid and various synthetic organic compounds such as butanol, pyridine and trimethylolpropane, amongst others. Good job a normal healthy body can metabolise it.

Formula. To calculate units of alcohol. The number of units of alcohol in a drink can be determined by multiplying the volume of the drink (in millilitres) by its percentage ABV, and dividing by 1 000.
For example, one 330ml of beer at 5% ABV contains 1.65 units of alcohol, arrived at as follows:
The formula uses ml ÷ 1000, which results in exactly one unit per percentage point per litre, of any alcoholic beverage.
(ml x ABV)/1000 = u (units of alcohol)

Since 5% can be expressed as .05, .05 × 330 ml gives the amount of alcohol in terms of ml—which, when divided by 10, shows the number of units.
When the volume of an alcoholic drink is shown in centilitres, determining the number of units in a drink is as simple as volume × percentage (converted into a fraction of 1).
Thus, 75 centilitres of wine (the contents of a standard wine bottle) at 12% ABV contains:
(750 x 12)/1000 = 9 units of alcohol
Note: you can shorten this by saying 75 x 0.12

It is true that a person who has eaten a full meal tends to show less alcohol in the bloodstream than, say, a person on a liquid diet. This is because the food volume in the stomach delays the processing of alcohol and holds it back from the small intestine where it would otherwise be absorbed more quickly. Nevertheless the alcohol you consumed will eventually enter the bloodstream and arrive at the liver for processing. That this takes longer means the person does not get so drunk. As to why women are less tolerant of alcohol concerns the production of acetaldehyde dehydrogenase during the metabolic process. Women simply have a lot less of this enzyme than men, so more alcohol enters the blood from the stomach, and so it will only be metabolised later by the liver, and at the same fixed rate.
And on a final note, what about all those ‘remedies’. There are none, really; no quick cures. Eating fatty foods, drinking lots of coffee will not speed up the metabolic process. When people drink too much it is normally at the expense of eating. Alcohol is also a diuretic, which is to say it leeches water from the body. Dehydration is one reason for a hangover. Residual acetaldehyde is another. Any food or extra fluid taken the morning after will redress the body’s energy, fluid and performance levels. But that’s all.

Copyright © Insurance Times and Investments® Vol:27.10 1st October, 2014
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