Diet sodas contain something many regular sodas don’t: mold inhibitors. They go by the names sodium benzoate or potassium benzoate, and they’re in nearly all diet sodas. But many regular sodas, such as Coke and Pepsi, don’t contain this preservative.
That’s bad news for diet drinkers. “These chemicals have the ability to cause severe damage to DNA in the mitochondria to the point that they totally inactivate it - they knock it out altogether,” Peter Piper, a professor of molecular biology and biotechnology at the University of Sheffield in the U.K., told a British newspaper in 1999. The preservative has also been linked to hives, asthma, and other allergic conditions, according to the Center for Science in the Public Interest.