There's a lot of nasty, virulent bugs going around this year. Colds and flus are putting people out of commission for weeks on end. This means that by now one of your friends has told you to drink some whiskey because that'll knock the cold right out.
Some people swear by it. But is there any scientific evidence to support that (admittedly fun) hypothesis? Let's see.
Knocking Out the Virus
First let's address the theory that after you're already getting sick, drinking whiskey (or brandy, or other spirits) will kill the virus and you'll wake up healthy. It's a beautiful idea, but unfortunately no study has ever shown that this is remotely true. Further, it doesn't make any logical sense at all. People think, "Hey, alcohol is used to sterilize stuff and kill viruses outside of my body, so why wouldn't it work inside by body?" The answer is has to do with concentrations.
Once you're already infected with a cold or flu virus, it's in your bloodstream. That means that if you want to kill it, you'd have to kill it in your blood. Yes, consuming alcohol does raise your blood-alcohol levels, but not nearly enough. According to the US Center for Disease Control (CDC), "Ethyl alcohol, at concentrations of 60%–80%, is a potent virucidal agent inactivating all of the lipophilic viruses (e.g., herpes, vaccinia, and influenza virus) and many hydrophilic viruses..." In other words, your bloodstream would likely need to be 60 to 80 percent alcohol (more alcohol than blood!) in order to kill your virus. When you consider that a blood-alcohol level of 0.2 percent is enough to put most people in a stupor, and bringing it up to 0.5 can easily cause death by alcohol poisoning, this is not a reasonable solution. You'd kill yourself before you'd kill your cold.
Soothing a Savage Throat
Theory number two. "Oh, you got a sore throat, bro? Throw back some whiskey and/or 151! It'll kill that itch real quick!" Thanks, dude. At least this one make a little bit of sense, in theory. Alcohol is used to disinfect surfaces. The surface of your throat is a surface! Q.E.D.! Except not really. A) The spirit probably doesn't stay on your throat long enough to really sterilize it, it's washed away by saliva. B) Even if it did, it would only clear the top part of your throat. When swallowing, liquid is passed down from your pharynx, through your oesophagus, and into your stomach. The thing is that most sore throats continue down your breathing pipe, not your food pipe, which is why they are so difficult to sooth. Trying to rinse the soreness away would lead to asphyxiation before relief.
So why does whiskey (and hot toddies and such) sometimes make your throat feel better? Mostly because it gets you a drunk. One of the by-products of even lower levels of intoxication is that you stop feeling pain so acutely. While this sounds nice, there are risks, aside from the usual drunken ones. First, alcohol is very drying. When you've got a sore throat or a cough, the last thing you want is your throat to be any drier. Dry tissues are far more susceptible to abrasions. Second, alcohol brings your blood vessels closer to the surface of your throat, which greatly increases the chance of damaging your delicate tissues. And third, you know how when you're sick everybody tells you to "push fluids"? Drinking alcohol is like "pulling fluids." It's a diuretic, which means you are likely to wake up dehydrated. No bueno.
An amusing anecdote. A certain family member of mine was in the Navy and stationed on a submarine. He woke up with a sore throat. He figured, "Hell, alcohol kills bacteria, I'll just gargle with some." In the Navy they had access to 99-point-something percent pure alcohol (for cleaning things, I assume). He tossed some into his mouth. It burned like hell. He immediately tried to spit it out, but the alcohol has sucked the water out of his cheeks and lips, puckering him so badly that he couldn't open his mouth, so it just kept burning him. Eventually he managed to get a couple fingers into his mouth, and was able to pry open his lips enough for the alcohol to dribble down his chin. My gene pool, ladies and gentlemen.
Now, this is interesting. There have been two studies which indicate that regular consumption of alcohol may actually make you less susceptible to getting colds in the first place (with caveats). The first study was conducted by Carnegie Mellon University in 1993 to see the relation between smoking, drinking, and susceptibility to the common cold. 391 subjects were "intentionally exposed to one of five respiratory viruses and 26 subjects given saline." The study concluded that smokers got sick more often, people who were smokers and drinkers got sick a normal amount, and people who just drank got sick less than the others.
The other study found somewhat different results. Published in 2001, the study looked at 4,272 faculty and staff of five Spanish universities. It found that alcohol intake in the form of beer and spirits had no effect whatsoever on a persons susceptibility to the common cold. However, the study concluded that people who drank more than 14 glasses of wine per week were a whopping 60 percent less likely to get sick, even more so for drinkers of red wine. That is a huge number. It is suspected, however, that it isn't the alcohol directly, but rather the high levels of antioxidants which are in the wine. If that's the case then drinkers of Guinness and other dark beers (which are high in similar antioxidants) might net similar benefits. It must be said, though, that 14 glasses of wine per week is not an insignificant amount (two per night, on average), and of course, there may be health risks that outweigh the cold-fighting benefits for some people.
We can reasonably conclude that if you're already sick (or getting sick), boozing ain't going to help you. In fact it may make things worse. That said, if you have a penchant for red wine, there's some evidence that suggests it may significantly boost your cold-fighting abilities. You may be able to get achieve the same results from grape juice, however. The jury is out on that one.
All that said, have I ever drank whiskey when I've felt a cold coming on and woken up in the morning miraculously feeling better? Yes. Is that good science? No. (Was it good whiskey? Yes.) I have also repeated the same "experiment" and woken up feeling much worse that I probably otherwise would have. Again, bad science, but the point is that results are wildly inconsistent at best. So, next time you're trying to go home early because you're feeling sick, and your friend is trying to sell you on staying out and drinking whiskey instead, tell him that his theories have no scientific basis! Nerd zing. That won't shut him up, but it'll make you feel better about yourself for going to bed at 8:30.