Q. Can one chew unflavored chewing gum on a fast day. It helps for one suffering from stress and also creates alertness. Does it depend on which fast day?
A. Poskim prohibit flavored chewing gum on a taanis (See Ohel Moshe 2: 113: 2, Mikve Hamaim 3: 47: 4 and others). However, totally unflavored chewing gum some permit, when being careful not to swallow it (Hilel Omar – O.H. 278, Likutei Kol Sinai – Bein Hametzorim 12 – quoting Horav O. Yosef zt’l, Miyam Hahalcha 1: 81).
There may be also considerations of maara ayin, since others watching don’t know it is unflavored chewing gum
Horav Shlomo Miller’s Shlit’a opinion is to avoid chewing even unflavored gum as it may contain other additives.
Rabbi A. Bartfeld as advised by Horav Shlomo Miller and Horav Aharon Miller Shlit’a