Ok, people should try to see what ReefHound is saying. I think there's a lot of prejudice and overexaggeration being thrown around on the subject of alcohol. Why not look at it objectively? I like to look at things objectively.
What are the deleterious effects that alcohol has on diving? 1) Alcohol will impair your judgement. 2) Alcohol will dehydrate you.
Let's look at those one at a time, and assess risks accurately and objectively...
1) Alcohol will impair your judgement. This is indisputable. How it affects every person will be different. Know though that everybody will be impaired in some small way, even before they can sense the impairment. Ultimately, it's up to you to decide, knowing your metabolism of alcohol, at what point the level of impairment is deemed an acceptable risk to you. Generally, one drink will be fully metabolized by the body in about an hour. Naturally this varies depending on a great number of figures, but is a good baseline to figure out when you may have fully metabolized the drink.
If you don't feel the slightest buzz after a single drink, chances are extraordinarily good that an hour or so after finishing your beer, you have very little alcohol in your bloodstream, and your impairment level is essentially nonexistent.
Unless you drank a six-pack or more the night before, 8 hours later, the effect of impairment is a non issue. Naturally, that brings us to the other issue with alcohol.
2) Alcohol will dehydrate you. Ok, but lots of things dehydrate us (food, salt, compressed air, heat, caffeine, etc, etc, etc), how do we put it into perspective? Well, since we're talking about beverage practices, let's compare alcohol to caffeine. Caffeine is regularly drunk by people before and between dives, but is certainly not frowned upon to the same extent. Let's examine objectively shall we.
For these purposes, we'll
assume that this study is correct (it's been cited by a lot of related studies, so I'll leave it to somebody else to try to debunk if they don't believe). According to that study, the diuretic effect of alcohol is 10ml extra water excreted for every gram of alcohol consumed, and that 1.17ml extra water is excreted for every milligram of caffeine consumed.
So, in an average bottle of beer (350ml) with an average (by American standards) alcohol percentage of 5% by volume, there are about 13.7g of alcohol in that bottle of beer. To compensate for the diuretic properties of that beer, you have to then consume an additional 137ml of water, or slightly less than one tablespoon (0.93tbsp). Compare that to the roughly 333ml of water being ingested with the alcohol, and you have a net gain on fluid balance. How this doesn't hold up when getting drunk, is that you'll have peed out your excess fluid you drank from say 8 beer, but you haven't gotten rid of the alcohol. That happens over the next 8 or so hours, which will dehydrate you, as you've no longer got the excess water in your system.
How does that compare to caffeine now? Well, a 250ml Red Bull has 80mg of caffeine, the larger 475ml ones (Rock Star, Xience, etc) are about double the size and have about double the caffeine at 160mg (some variants go even higher). A 475ml grande Starbucks regular coffee has anywhere from 250mg to 550mg!
What does that mean? How much extra water does the caffeine make you excrete? Red Bull: 93.6ml, Rock Star: 187.2ml, Starbucks: 290-640ml! Now, except for an exceptionally strong brew of Starbucks, drinking a single serving of any of these really isn't going to have a net negative effect on your fluid balance. Further, studies have shown that there is
"no support for the suggestion that consumption of caffeine-containing beverages as part of a normal lifestyle leads to fluid loss in excess of the volume ingested".
What does all that mean? Well, that the diuretic effect of one drink of alcohol is pretty close to that of one drink with caffeine, and that the effect of that on your fluid balance is essentially a non-issue.
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So, please take this information for what it's worth. Please do your own study and generate your own risk threshold. Hopefully it will serve to shed light on a lot of the assumptions and hyperbole being thrown around.
Craig
PS: Personally I don't want to drink anything for several hours before diving, a beer at lunch before a night dive would be about my limit. I'll have a few beer the night before, so long as it's accompanied by a decent rest period, and as always, plenty of water. But I'm not too worried about being dehydrated.
Due to the fact that we are recreating in an alien environment, I will not take guests diving when I am impaired and I will not take anyone diving if I know they are impaired.
). My accident management training leads me to believe that water is over-rated and High-C is the best post-dive hydrator, due to the high sodium content. A well known diving scientist, with the nads to form his own training agency, told me a saline solution is what flushes nitrogen best. Most sports drinks also have some sodium (not as much as High-C), but beer and pretzels is not a bad way to go, just don't pee until you really really have too.
