What is a standard alcoholic drink?

By Anna Sandiford 06/11/2013

What IS a standard alcoholic drink?  It’s a nightmare, that’s what it is.  As a forensic alcohol toxicologist, the concept of a standard drink is somewhat arbitrary and inconsistent because the people drinking them differ in physical stature and biological processing ability so the alcohol in a standard drink contributes a different amount to people of different genders, heights and weights.

A standard measure of spirit in New Zealand contains 70 ml (because they usually serve them as a double measure).  Jim Beam contains 40% alcohol by volume.  70 ml of Jim beam contains 22.12 g of alcohol.  If a standard drink contains 10 g alcohol then 70 ml Jim Beam contains just over two standard drinks.  That’s the easy bit.

It gets difficult when considering what that alcohol would contribute to a 58 kg, 168 cm woman’s blood alcohol concentration or a 95 kg, 183 cm man.  The answer for the woman is approximately 69 mg alcohol/100 ml blood.  For the man it is approximately 34 mg alcohol/100 ml blood (maximum figures, assuming no metabolism).

How then to convert a standard drink into suggested drinking levels for the public as a whole?  Fraught with difficulty.  I understand the need to give people a measure they can understand, but smaller, lighter people need to be more wary of ‘standard drink’ suggestions.  As do people who don’t drink often, people whose liver function is impaired, people who metabolise alcohol at a lower than average rate (which you can’t tell by looking at someone) – the list goes on.

Once again, be aware and if in doubt, don’t drink and drive…