by Alanna Nuñez for SHAPE.com1. Potassium benzoate: When you crave something sweet, bubbly, and perhaps caffeinated but don't want the calories, it can be tempting to crack open a diet soda-but resist that urge. "Sodium and potassium benzoate are added to some diet soft drinks and fruit drinks," Leslie Bonci, R.D., says. "They can form benzene, which is a carcinogen when combined with vitamin C, the ascorbic acid in juice or soda. ...