I have a bud light in a friend's refrigerator that has a date of May 14 2007. I have heard of people drinking beer after the posted date, but does it turn harmful after all these years if I drink it?
The pH of beer is low enough that no known pathogens can survive in it. That's why you never hear about botulism problems with home-brewed beer like you do with home-canned foods, for example.
Beer slowly changes over time. High gravity beers, like barley wines or imperial stouts benefit from this, and acquire richer flavors as they slowly oxydize. Belgian styles, like lambics do as well and the wild yeasts and bacteria continue to grow. However, even those have a limit -- eventually they will begin to taste very stale.
Low gravity beers begin to taste stale much more quickly. If you are keeping them refrigerated, they may last for 6 months or more. Seven years is definitely way too long.
So it won't make you sick or harm you if you want to taste it. But it is extremely unlikely that you will enjoy it.
I've drinked beers that were 2 years past the sell by date. They tasted normal (although i´m not a beer sommellier) and nothing bad happened to me, as other answers have pointed out.
If i were you I would see this as a unique oportunity to test how 7 years of bottle aging change a Lite American Lager. Buy a brand new Bud Light, refrigerate it to the same temperature, open both bottles, pour into equal glasses and see. If they look similar (same color and foam) and the old one doesn´t smell bad, give it a small sip. If it tastes normal, there's no reason for you not to try it! In case you really compare them, can you share with us the differences in color, smell and taste between the new and the 7-years old Bud Light?
No pathogens can survive in beer. But the beer may taste off. Remember that the Pilgrims survived the journey across the Atlantic because they had beer, not water, since beer stays drinkable much longer due to the alcohol and hops that act as preservatives. Nothing will happen to you if you drink that beer.
I would drink it, if it wasn't Bud Light ;-) I had old beer before, probably 2 years after expiration. If the pressure is still there when you open it and if the can/bottle has no dents/rust/etc there shouldn't be an issue. They found a WWII food can and it was still edible when they opened in 2013, tested by a lab. Obviously taste is a different issue. There may be some deterioration. If it smells like vinegar you'll know it's bad
This is a couple years behind the topic. What the heck. I've got 3 aluminum long neck bud's, Not that light stuff either, from 2006. I'm straining them through a coffee filter just in case. 1st thing I noticed was the color. Much darker than a new bud. 2nd is the smell. Strong alcohol smell you don't get with beer. Makes me wonder if fermentation was still active at a later point. Wish I had a way of checking the alcohol lv. After about 20 oz consumed I'll have a close enough guess. Waiting til after work around 11 or 12. I'll put in an update. 9 year old beer. This sounds like fun.
I am Tom Sawyer
Sell by dates tend to be very conservative to cover peoples asses, but in reality many beers will actually get better past their sell-by date, particularly unfiltered (cloudy) beers.
Beers like any of the light lagers should be fine for a year or two and not taste significantly worse provided they are stored properly.
Improper storage would be somewhere with warm or fluctuating temperature or where the beer is exposed to light. Light is what "skunks" beer, and can literally synthesize the same chemicals that makes skunks smell.
The color of the bottle has a big effect on how rapidly this can occur. Clear glass provides no protection, I would not drink Corona that was left in the sun for even just one day (not that I wouldn't avoid it anyway). Green provides some, but is not much better (blocks somewhere around 40% of light). Brown is the best blocking around 90% of light, but completely opaque materials are the only things that are truly effective. Some breweries like Sam Adams even go the extra mile and have extra tall sides on their six packs to block light completely.
In short, old beer is not dangerous. Some styles age well (belgian styles, german wheat, unfiltered styles). Others do not (light lagers, pale ales, filtered beers). Light is the real enemy.
As far as I've ever tried, old beers, even cheap light lager like Bud Light, will taste pretty off after a lot of in-bottle or can aging. The older it is, the worse it will taste, but having drunk more than one in a sitting, I can safely say it's no more harmful than drinking a fresh one. Never gotten sick off one, but it's pretty hard to down them without gagging a bit.
Some beers actually seem to intentionally go for a similar taste. Anything with a green bottle seems to be trying for a skunky flavor, while brown bottles help filter out damaging light. Compare a Beck's or Heineken to, say, a Budweiser. The former will have a distinctly skunky flavor to them, basically similar to marijuana. The latter has a bit of a rice taste, as that's what's used in the brewing process, with a slight sweetness, but overall just a bubbly light flavor.
As Linus pointed out, there's going to be a "wet cardboard" taste with past-due light lagers. I'm guessing this is due to the breakdown of oils and sugars in the beer, as well as other general chemical changes. I'm not sure why it has that taste of cardboard or paper, but it's definitely present. After doing some research (aka looking it up on google), I found that the main culprit of that cardboard taste is a chemical called "nonenal". It's apparently also a chemical in human body odor of aged people, leading to the so-called "old people smell". This isn't proven, but there's some evidence that this is the main culprit for the somewhat-neutral scent of older people's perspiration. In a beer, not quite as neutral, however.
It is unlikely to be harmful (assuming it hasn't become infected), but the flavour may have changed compared to fresher bottles of the same brand. In particular, the aromatic oils from the hops will break down as the beer ages.
Whether this makes the beer undrinkable will depend partly on the beer and partly on the tastes of the person drinking it. If you are curious you may as well try a mouthful or two.
Here's a video of someone attempting to drink a beer from 1988 - it didn't go over very well for him.