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Slightly different question but something that occurred to me recently.
it seems that beer only needs to be 0.5% or less to be advertised as “alcohol free” and some 0.3% ones are labeled as “0.0” until you look close.
Given that the driving limit in Scotland / Europe is very low and these beers do contain a small amount, is there a situation where you could drink 5 or 6 “alcohol free” beers and still be approaching drink driving?
What actual amount would 3-4x be, in pints? (Or bottles of wine, or whatever!
Assuming 1.5 pints of beer is about the legal limit for the average human (massive simplification I know but go with it), 3-4 x quite a lot. I think I'd struggle to drink that much alchy free beer in one sitting and I think I'd know that it wasnt alchy free by how wobbly I got and how much I felt the need for a filthy kebab on the way home 😉
Actually it's pretty easy because the dose (grammes) is so high that metabolism is saturated - and hence linear at about one unit per hour. It's why back-calculation is allowed to predict what you would have been at the time of an accident.
Yes, I should have phrased my post better. Food and still drinks tend to slow alcohol getting out of your stomach, which makes barside approximation harder because blood alcohol might still be rising as you drive home
We were also told that fat distribution and size (often sex-related) affects metabolism. Is that your experience?
What actual amount would 3-4x be, in pints? (Or bottles of wine, or whatever!
Assuming 1.5 pints of beer is about the legal limit for the average human (massive simplification I know but go with it), 3-4 x quite a lot. I think I'd struggle to drink that much alchy free beer in one sitting and I think I'd know that it wasnt alchy free by how wobbly I got and how much I felt the need for a filthy kebab on the way home 😉
I just realised, reading your reply, what an odd question I asked, but I never drink and drive so have never really needed to think about it before. Yeah, maybe 5ish pints upwards, dependant on which beer.
Slightly different question but something that occurred to me recently.
it seems that beer only needs to be 0.5% or less to be advertised as “alcohol free” and some 0.3% ones are labeled as “0.0” until you look close.
Given that the driving limit in Scotland / Europe is very low and these beers do contain a small amount, is there a situation where you could drink 5 or 6 “alcohol free” beers and still be approaching drink driving?
The blood alcohol driving limit in Scotland is 0.5 g/L.
A pint of 0.5% alcohol contains: about 2.2g of pure ethanol.
There is a rule of thumb that blood alcohol = ((g of EtOH) / V)- B*T where V is the volume of the person, B is rate your body can get rid of it, T is the time. V averages 0.71 x weight in kg for a typical man (women are 0.58 L/kg) . So lets say 80kg = 56.8L
That means IF you could instantly consume your very low alcohol beer have it instantly make it through your stomach and immediately get in the car you would need to consume nearly 13 pints to reach the Scottish limit. B is usually about 0.15g/L/hr so you can consume almost 4 pints of 0.5% ABV per hour without your blood alcohol increasing.
I should say thats based on lots of averages and estimates and extrapolations which are probably not entirely linear but if anyone can consume enough "alcohol free" beer to blow above the Scottish limit they are probably forgetting to mention the vodka they had before they went out!
Slightly different question but something that occurred to me recently.
it seems that beer only needs to be 0.5% or less to be advertised as “alcohol free” and some 0.3% ones are labeled as “0.0” until you look close.
Given that the driving limit in Scotland / Europe is very low and these beers do contain a small amount, is there a situation where you could drink 5 or 6 “alcohol free” beers and still be approaching drink driving?
The blood alcohol driving limit in Scotland is 0.5 g/L.
A pint of 0.5% alcohol contains: about 2.2g of pure ethanol.
There is a rule of thumb that blood alcohol = ((g of EtOH) / V)- B*T where V is the volume of the person, B is rate your body can get rid of it, T is the time. V averages 0.71 x weight in kg for a typical man (women are 0.58 L/kg) . So lets say 80kg = 56.8L
That means IF you could instantly consume your very low alcohol beer have it instantly make it through your stomach and immediately get in the car you would need to consume nearly 13 pints to reach the Scottish limit. B is usually about 0.15g/L/hr so you can consume almost 4 pints of 0.5% ABV per hour without your blood alcohol increasing.
I should say thats based on lots of averages and estimates and extrapolations which are probably not entirely linear but if anyone can consume enough "alcohol free" beer to blow above the Scottish limit they are probably forgetting to mention the vodka they had before they went out!
That makes sense. Had totally not thought about the rate of the body processing it!
thanks for the explanation!
Drink driving limit is 80 mg per 100mL or 800 mg per litre. Typical alcohol volume of distribution is 55% of bodyweight* (70 kg) so 38.5L, implying a dose [g] of 38.5[L]*0.8[g/L] = 30.8g. And one unit of alcohol is 8g (10 mL) - hence 3.85 units (approx. 1.5 pints). And that's immediately on board ignoring any elimination. And is an average for a typical 70kg adult of normal adiposity. To be 3-4x over the limit you would need to neck 11-15 units in an hour. Half a bottle of spirits in an hour would finish off most people. Remember that alcoholics function with high blood alcohol levels.
There are corrections for sex, weight, adiposity, drinking history. But people are not THAT variable. Livers come as relatively standard and it's one unit per hour perhaps about half as much again for a heavy drinker due to induction. and you can't rely on any of those for a defence in back calculation (except bodyweight)
* More recent discussion here https://onlinelibrary.wiley.com/doi/10.1111/1556-4029.15317 puts the volumes a bit higher and of course sex dependent. It'a basically water content. there is subtlety in how volume is calculated due to the non-linearity of the elimination when levels reach 20 mg/100mL. Classic paper by Nick Holford on this https://pubmed.ncbi.nlm.nih.gov/3319346/
There is a rule of thumb that blood alcohol = ((g of EtOH) / V)- B*T where V is the volume of the person, B is rate your body can get rid of it, T is the time. V averages 0.71 x weight in kg for a typical man (women are 0.58 L/kg) . So lets say 80kg = 56.8L
The biggest question I have about this is: why is the typical woman so much denser then the average man? I know we have different physiology, but didn't think it would be that big!
it’s not technically that the density of man/woman varies - rather it’s the volume which blood gets into (blood v fat/bone). In fact if you were getting an expert witness to explain your particular situation in court you expect they don’t focus on gender as the main differentiator but would have better ways of estimating for the individual, but for the purposes of a demonstration calculation one number for men did the job and the woman’s number highlights that the result for people of different build and physique will be different but not orders of magnitude different.There is a rule of thumb that blood alcohol = ((g of EtOH) / V)- B*T where V is the volume of the person, B is rate your body can get rid of it, T is the time. V averages 0.71 x weight in kg for a typical man (women are 0.58 L/kg) . So lets say 80kg = 56.8L
The biggest question I have about this is: why is the typical woman so much denser then the average man? I know we have different physiology, but didn't think it would be that big!