Monday, March 24, 2008

How Much Can You Drink?

There is considerable evidence that consumption of alcohol can have beneficial health effects, however as we have seen the recommended consumption differs between countries. Here in the USA it is two standard drinks for men with a standard drink being 13.7 grams of alcohol; this is often rounded out to 14. But not all wines have the same alcohol content, usually expressed as percent alcohol by volume (ABV). How much does alcohol content affect the volume of wine that I can drink to get my two standard drinks, or 28 grams of alcohol?

Calculating the volume of alcohol in milliliters (mls) in your wine is quite simple. If a wine is 12.5% ABV that means that 100 mls of wine contains 12.5 mls of alcohol. If its a 14% wine then it will contain 14 mls of alcohol/100mls of wine. However the volume and weight of alcohol are not equivalent; alcohol is less dense than water. So to get grams of alcohol you need to multiply the volume by the density of ethanol (0.789 grams/ml). So 100 ml of a 12.5% wine contains 9.86 grams and for a 14% wine it will be 11.05. The table below shows how much you can drink in standard drinks (5 ounces or 150 ml) or in volume (in mls) to reach that magic number of 28 grams of alcohol for wines between 12.5 to 16% alcohol by volume.

Alcohol by volume*Alcohol by Weight**Standard Drinks to reach 28 grmsVolume (mls) to reach 28 grms

12.5

9.86

2.8

420

13.0

10.26

2.7

405

13.5

10.65

2.6

390

14.0

11.05

2.5

374

14.5

11.44

2.4

360

15.0

11.84

2.35

352

15.5

12.23

2.3

345

16.0

12.62

2.2

330

*mls/100mls; **grams/100mls

But what if you want to exceed 28 grams? How much can you consume before your blood alcohol content (BAC) exceeds the legal limit. There is absolutely no doubt that equivalent consumption of higher alcohol wines will increase your blood alcohol content but what are the limits with wines of different alcohol content? For these calculations I have used the BAC from Celtic Kane simply because it allows input of a number of variables including alcohol level of the wine, number of drinks, time elapsed during drinking,etc.

Warning: BAC calculators are an estimate only and no one should assume that they are absolutely correct as they do not consider all factors involved.

As a 750 ml bottle contains 25.4 fluid ounces let’s say that a half bottle is 12.7 and if we pour a 5 ounce glass (150 mls) then we would consume 2.54 glasses; these numbers are all for convenience, anyone can add their own numbers to work out their BAC under different situations. I’ll use my weight (170lbs), a metabolic rate of Frequent Drinker, and an elapsed time of 2.5 hours; roughly a glass an hour which is about the speed I drink while having dinner or watching an hour or two of TV or doing some reading.

If I’m drinking a 13% alcohol wine my BAC would be 0.019. For a 14.5 %er it would be 0.027, and if I’m sipping on a monster Zinfandel or a high octane Shiraz of 16% my BAC would be 0.035. The difference between the 13 and 14.5 % wines is not that large; for example the time to achieve complete sobriety differs by less than 30 minutes. As expected the 16% alcohol wine will raise my BAC more but I’m still not legally drunk and in less than 2 hours I should be completely sober; with the 13% wine I’ll be completely sober in just under an hour, and in less than 1.5 hours for the 14.5%er.

If I drink 4 glasses at 5 ounces a glass then the 16% will make me just legally impaired at a BAC of 0.084, while the 13 and 14.5 % wines will not. But we are talking about daily wine drinking that uses commonsense rather than consumption for its own sake.

Of course all this assumes that the wine level on the bottle label is even close to being correct. A wine labeled below 14% can have a 1.5% variation over or under, while a 14% wine can have a 1% variation. So a 13.9% wine could be a 15.4%er, and a 14.5% wine could be a 15.5% wine.

Considering my own experience I don’t suffer any ill effects from consumption of between 2-3 glasses of (dry) wine per day; I’m sure everyone’s mileage varies on this point. However I would not drink three 5 oz glasses of some of my favorite Australian fortified wines that can be 18% alcohol, even though my BAC would only be 0.063. The reason? As much as I love them, sometimes too much of a good thing does dull the appreciation.

3 comments:

Orion Slayer said...

Interesting post, thanks. I've wondered about how much I could safely drink and your article gives a good starting point for figuring that out.

I just read yesterday about how the ability to motabilize alcohol changes as we get older. Ours bodies can't handle the same amounts at 65 that we could handle at 45. I couldn't find a link to the article I read but here is a story that shows the same findings.

Have you read anything that talks about how much alcohol is absorbed into our bodies by just tasting wine and spitting? I've felt safe going to a wine tasting where I tasted and spat and then drove, but now I'm beginning to worry. Any idea how much you can taste and spit before you begin to become imparied?

Mike said...

orion slayer,
Thanks for your comment. I have not seen anything on BAC if one spits rather than swallows wine. I’ll try to see what I can find. I know from personal experience that spitting does make a considerable difference, especially if you are spending a day tasting, in wine country for example. Of course the real trick is learning to spit without dribbling down the front of your shirt.

Arthur said...

Mike,

First, for once, I can say that I do not have a major disagreement with what you are saying in this post.

Second, if you wish to protect your clothing, I recommend a "Stainproof" Wine tasting Shirt.

;)