View Full Version : BAC without alcohol consumption

29th Dec 2003, 02:18
The latest GASIL ( makes the following claim with reference to the new rules on blood alcohol concentration and flying:

The human body manufactures its own alcohol, and it is possible for the level of that ‘selfmanufactured’ alcohol to almost reach that 20 milligram level, so it would be prudent for anyone who is subject to the Act to think of the permitted level as equating to no consumed alcohol at all.

I've never heard of such a thing, and would be interested in references to literature that reports the distribution for a sample population of background blood alcohol concentrations in the absence of alcohol consumption.

29th Dec 2003, 04:35
had a scout on the medical databases and couldn't find anything useful. If you have some spare time check out this database ( . Try using key words like "alcohol" and "self manufactured" with connectors such as AND and NOT. Its a bit of a pain, but if its been published you will probably find it here.

Failing that, ask a physiologist ! The ones at Liverpool University Medical School seem quite friendly !!

29th Dec 2003, 15:24
Thanks gingernut. I tried Medline before posting, but couldn't find anything. I now find that the magic word appears to be endogenous.

This article ( has some useful references including a paper ( by AW Jones (who appears to be the expert in this area) assessing the baseline BAC in the absence of alcohol consumption as 0.04 +/- 0.04 mg/dl, compared with the proposed limit of 20 mg/dl.

While GASIL can, if it chooses to defend its literal statement, hide behind the fact that higher concentrations have been recorded in extraordinary individuals, it is extremely misleading to suggest that ordinary people's bodies manufacture their own alcohol at a level that is of any significance to flying BAC limits.

30th Dec 2003, 00:00
Hi BW,

You know I am only a simple quack but I have never heard this before and would be interested to see the evidence on which GASIL bases its assertion.

A discussion regarding this was recently had on a different BB and I wrote there that it is well documented that people after their demise start producing alcohol. However that is only of importance for post accident investigations as the distribution across the different tissues can give an indication on whether alcohol was present at the time of the accident or not.

I have yet to come across any article or evidence that endogenous alcohol production is a possible contribution to people being over the blood/alcohol limit.

Am pretty sure that if there was any mileage in this we would have seen defense cases being set up along these lines for well heeled drink drivers.

Would be keen to find out more if you come across it will have a look if I can find more but if Medline came up without anything I suspect there will not be a lot out there.



30th Dec 2003, 00:19
Also consider that endogenous alcohol is brewed up in the gut, it then travels directly to the liver where a significant amount is metabolised in the "first pass" effect. Plenty of alcohol dehydrogenase in the gut wall too. I'd be surprised if much of the low level of alcohol found in gut-fermentation got through the liver, but that's just my supposition.

This unfortunate effect can be avoided quite nicely by swilling a strong whisky around in your mouth without swallowing it. You get a nice buzz as the alcohol goes direct from the mouth to the heart to the brain. More of a student trick, now one can afford to swallow and take the loss :)

Anyway, even if the pilot claims he is over the limit because of endogenous alcohol he is still over the limit and so unfit to fly. If he claims to be one of the rare people who may truly be affected by endogenous alcohol, I think that would be as medically disqualifying as being epileptic.

30th Dec 2003, 00:58

I think that there is only very little fermentation in a normal healthy bowel.

Of course there are people with bacterial overgrowth etc that will be producing more ethanol but not convinced that is a real issue with regards to BACs.


30th Dec 2003, 02:24
Sure FD, I agree with you, the only reason you will be 'over the limit' is because you ingested alcohol.

However alcohol dehydrogenase must be in the gut wall for a reason, and I bet it "evolved" there before humans worked out how to make booze. So it's probably there to keep naturally occuring low levels of endogenous alcohol away from the CNS. I wager that GASIL didn't consider the physiology described in my first post when making their rules up.

So they got it right, but for the wrong reasons.

Now I'm just waiting for some party animal airline pilot to cite Borkenstein and Grand Rapids for it being OK to be half cut when reporting for duty :)

30th Dec 2003, 05:21
Flyin'Dutch' - I have a friend who is a UK magistrate ( :p ) who told me that one case was dismissed as the accused PROVED his BAC was 80+mg in his natural state! I personally could not see how this person could be permitted to drive at all, but he/she was.
I guess that is a touch unusual!

30th Dec 2003, 07:17

I am always a tad suspicious of these tales.

Show me chapter and verse and I will believe it.

Don't doubt you but there are quite a few urban legends floating about and call me old fashioned, I don't want to fall for them.


Chocks Wahey
30th Dec 2003, 08:48
I have worked on the railways for over 20 years and about 12 years ago the government introduced legislation that made all staff aware of the need to show due diligence with regards to colleagues under the influence of drugs and/or alcohol. Management were also required to introduce a programme of random unannounced testing. There was and still is a zero tolerance policy with regards to any amount of drug taking but the limit for alcohol was just under the legal drink drive limit.

London Underground imposed a total zero limit on alcohol and dismissed a large number of staff for being drunk on duty, this despite strenuous denials from some of the staff involved. The subsequent appeals only upheld the sackings. Then it happened that a senior manager was dismissed for being under the influence of alcohol whilst on duty. The manager also happened to be tea-total and had never drunk alcohol in his life. He sought scientific advice and to cut a long story short found that the body does indeed produce natural alcohol. This was presented to an industrial tribunal and the manager was re-instated. London Underground have since amended their policy to the current statute standards and paid out thousands in compensation to it's sacked employees.

Don't know if this will help anyone or where you can find any information on the body producing alcohol but I know it does happen hence the shift in LU policy. I don't think the aviation industry has much to fear from random drugs and alcohol testing. Only those that abuse D and A should worry. If aviation follows the railway example and allows those with a problem to come forward in confidence and admit it (pre test day) and help them out, then it can only be a good thing.

30th Dec 2003, 16:26
He sought scientific advice and to cut a long story short found that the body does indeed produce natural alcohol. This was presented to an industrial tribunal and the manager was re-instated

I have no reason to believe that any of this is not true.

But being reinstated by an industrial tribunal is not necessary the same as being able to prove something scientifically.

I have been trawling through the net about this and can not find anything substantial which would support this point of view.

My skepticism tells me that if this was a viable defense, thousands a year would use it to avoid convictions for drink driving offenses. After all the only thing your barrister would have to do is quote the scientific evidence (as presented to the industrial tribunal) and away you go.

I recently attended an AME seminar organised by the FAA and we discussed 'false positive' tests for Marijuana derivatives after eating 'food supplements', nobody mentioned the same for alcohol.

DUIs are a very hot topic for the police and the FAA, and I again am pretty sure that if this 'endogenous alcohol' was an issue that there would be more interest in it both from the enforcement side and defence lawyers over there.

Happy to look at any articles to be convinced otherwise, but for now remain sceptically.


30th Dec 2003, 19:41
Jones, A.W (1985. J. Anal. Toxicol. 9:246) found endogenous levels are from undetectable up to 0.02 mg/dl

Lester, D. (1962 Quart. J. Stud. Alcohol 23:17) found they could be up to 0.15 mg/dl

Compare with legal limit of 80mg/dl for a car driver, and 20mg/dl proposed for airline pilots. Not even close, better excuses needed ...

10th Jan 2004, 19:12
I believe the Gasil comment is ill-informed and a red herring.

However, I am concerned that the legislation mentions urine testing.

Presumably, the justification for testing is to determine impairment (of function). Yet the levels set for alcohol are at the "zero tolerance" level i.e. not simple impairment.

This is an important distinction, for example, Urine testing does not determine impairment. Hence it is possible for both breathe and blood testing to be negative, whilst urine may test positive.
Hence a urine test would not make a suitable primary or confirmatory test for alcohol impairment in court.

Note also that "drugs" are not defined, nor is any level set for drugs. This is potentially very worrying. If "zero tolerance" levels were set for "drugs" too (probably including some legal over the counter drugs) then many individuals would test positive many days after imbibing. There are so many problems with this, that it may make treatment, rehabilitation and return to duty of any individual problematic.

11th Jan 2004, 02:58

There are also sites which detail the arrest of drivers in the US for having more than 0.1% blood-alcohol who were subsequently cleared
Go on then, I would be keen to see those.

As Candida is a yeast, it produces alcohol ...........................If however you have an overgrowth of intestinal candida, the levels of alcohol entering the bloodstream are going to be greatly increased.

Just because it appears in black [blue!] and white on the internet does not mean that it is true.

When looking at sites it pays to see who promotes this 'information', surprisingly this site sells some books on this matter!