According to the French coach, the sickness swept the Arsenal camp, coupled with the severe heat in China and extensive travelling to different climates wasn't "ideal physically" for the players.
Olivier Giroud missed Wednesday's friendly victory over Bayern Munich because of food poisoning, then captain Per Mertesacker pulled out of the game just moments before kick-off because he too fell ill with the same problem.
New signing Sead Kolasinac also had to come off before the break and second-half substitutes Theo Walcott and Aaron Ramsey both finished the game not feeling well.
During the game, the Arsenal team were poor in the first half in the 36 degrees Celsius (97F) heat and Wenger admitted that the extreme conditions in Shanghai were "a shock" after flying in from Australia, which is in its winter
"I was a bit scared that tonight we could have big problems and in fact in the first half we suffered a bit," said Wenger.
"Ramsey finished the game, but Walcott, Kolasinac, Mertesacker, Giroud, they all had a little food poisoning."
Wenger said the club did not know what caused the food poisoning.
Wenger added of the punishing preseason schedule that many top European clubs now undertake to far-flung destinations for commercial reasons: "If you ask me is it ideal physically to prepare? I'd say certainly not.
"Has it got other advantages? Yes because we can meet fans all over the world so that is very positive."