Jackson, who spent time on loan with Coventry recently, was offered a transfer to the Chinese team, Dalian Wanda, last month. However, the 32-year-old, who played twice for Scotland at the World Cup last summer, decided to return to Glasgow at the weekend after a trial with the Chinese club.
"I went out there on a conditional contract and the Chinese were fantastic and treated me very well. But I am not the best of eaters at the best of times and the food wasn't what I am used to," Jackson said.
"I felt I wasn't eating properly and I wasn't myself. I wanted to come back after a day but I felt I had to give it a go and I lasted eight days. But it wasn't for me and I came back."
Having played only three games as a substitute in his loan spell at Coventry, Jackson faces a huge task to persuade Jozef Venglos, the Celtic head coach, that he merits renewed consideration for a first-team place.
"The boys are doing very well and I know it is going to be very hard to get back in," Jackson said.