In a 2016 article at the Science of People, Vanessa Van Edwards reviews the benefits of chewing gum. As she reports, chewing gum can make you more alert, resulting in improved reaction times, improved productivity, and better cognitive performance on a test (but only when gum is chewed before—not during—the test). (Other studies have also shown negative effects on memory while chewing.) Chewing gum can also improve mood and reduce stress.
While it’s certainly not a good idea to chew gum while you speak, this research suggests that if it’s something you like to do, it may be good to do it before you speak (ideally in the 15-20 minutes before your speech, as that’s how long the cognitive benefits last), simultaneously making you more alert and ready to perform, while improving your mood and reducing stress.