"Mountain Dew'll tickle yer innards, cuz there's a bang in every bottle!" That's what the hillbilly spokesmascot for the carbonated beverage used to say in this old TV commercial for the "Sof' Drink."
I thought the "bang" was the added caffeine (54 mg per 12 oz ounce serving as compared to 34 mg for the same amount of Coca-Cola) but it turns out to be brominated vegetable oil, which contains bromine.
Sadly, our friends in Japan and the EU can no longer enjoy Moutain Dew or the equally delicious Fresca, because food containing bromine is banned in those places.
From Mayo Clinic:
Brominated vegetable oil (BVO for short) is a food additive sometimes used to keep citrus flavoring from separating out in sodas and other beverages.
…there have been reports of people experiencing memory loss and skin and nerve problems after drinking excessive amounts (more than 2 liters a day) of soda containing BVO. While few people are likely to drink such large quantities, concern exists because bromine appears to build up in the body.