Q: How does altitude affect the taste of wine, and how wine affects us? —Steven B., Czech Republic
A: First up, I need to squash the rumor that drinking alcohol at high altitudes will make you feel its effects sooner—multiple studies have proven that altitude alone does not have an effect on alcohol's potency. That's not to say altitude won't make you feel funny: I've personally experienced that light-headed, lethargic feeling of "altitude sickness." Understand that oxygen levels become less dense and start to thin out the higher you rise. This can result in hypoxia or lack of oxygen to the brain and muscle tissue. And a glass of wine on top of that will certainly amplify those feelings.
The biggest difference about high altitude is the dryness—you'll need to drink plenty of water, because wine will also dehydrate you, and if your nose and palate are dry, they aren't working as well and a wine's flavors can seem dull. Altitude can also make a wine seem unpleasantly sharp with tannins. Typically, tannic wines cause us to salivate, as a way to reduce their astringent effect. But if you're dehydrated, you're going to have trouble producing that moisture you need, so the wine might seem more tannic.
Then there are the high altitudes of air travel. Enjoying wine is especially bad in a pressurized plane cabin, where the reduced air pressure and lower oxygen can cause a wine's aroma to dissipate more quickly. In a plane, acid and tannins can really stick out, so airlines tend to pick fruity wines that aren't too tannic or acidic. As a fascinating aside, airplanes are also very loud, and studies have indicated that loud noises can distract from our ability to taste (and also offers at least a partial explanation for why airline food can be so disappointing).