Its still completely plausible IMO. He never showed big interest in Klingon cuisine until he met Jadzia. He was raised by his humans, probably with human food. He might not even know that his bowel movements are irregular/unusual, since talking about shit isnt exactly a topic of honor he would discuss with other Klingons. And he always lead a pretty conservative lifestyle, avoiding change whenever possible. Why should he randomly change to a klingon diet?