Duterte defended the habit regarded by many as a rude gesture as part of a health regimen, the Philippines' GMA network reported.
"It eases up [spinal] pain when I'm chewing," Duterte said in a statement that included phrases spoken in his native Tagalog. "It eases a bit."
In 2017, Duterte was seen on video footage chewing gum while meeting with Xi.
A subsequent meeting Japan's Emperor Akihito did not take place.
Media cited Duterte's gum chewing as a possible reason for the cancellation.
Duterte has spoken previously about his health, including back pain, but he has yet to undergo surgery.
The Philippine leader has said he "pushes a nerve behind his ear" and uses Fentanyl for pain relief, according to GMA.
Duterte's meeting with the Japanese emperor, who does not play a governing role, may have been an important one, as Tokyo is a major provider of development assistance to Manila.
But the Philippine president has not ordered the removal of a statue dedicated to Filipino "comfort women" who may have been raped or abducted to Japanese wartime brothels, Rappler reported Thursday.
"It's not something the president will act on himself. We didn't erect the statue so it's not a presidential project, so to speak," presidential spokesman Harry Roque said.
On Tuesday visiting Japanese official Seiko Noda said the statue was "regrettable," and the Japanese embassy in Manila has expressed concern about its unveiling.