Tea has so many health benefits that it's rare you'll find anyone disrespecting the Asian brewed drink -- but then Americans took something that's basically amazing and decided that we need to infuse it with lemons and massive quantities of sugar, make it ice-cold, and drink it that way rather than with the typical Asian respect. To be honest, much of what we refer to as 'iced tea' -- especially anything you make by mixing a powder into water -- has basically nothing to do with actual tea. It's a flavoring, and it's usually mostly artificial.
The problem with iced tea isn't limited to its extra acid from the lemon
and how all that added sugar promotes the growth of Streptococcus
Mutans (the bacteria that causes plaque, tartar, and gingivitis) in your
mouth. It's also in how we drink it. Like all bacteria, Streptococcus
Mutans has a limit to how fast it can multiply in your mouth -- and it's
also limited by its supply of fuel.
Because the tradition with iced tea is to lean back on the porch or
around the picnic table while you watch your son's Little League team
whup its competitors, you're essentially creating a worst-case scenario
in your mouth. You feed those bacteria a few sips of sugar every minute
or two for an hour, giving them all of the time and fuel they need to
make a huge, military-style advance against your gum line.
Now, if you make your tea by actually making real tea (Green is best
unless you're strictly avoiding caffeine) and then adding ice and a
small amount of added sugar, you can totally enjoy that knowing you're
doing right by your mouth. But instant, prepackaged, or other iced
"teas" aren't going to leave your mouth feeling its best.