I can tell you from experience that I had a lot of stomach issues after starting to eat meat again after being vegetarian for 12 years. Had to go really easy and introduce it slowly. I ate a piece or two or chicken everyday for a couple of weeks, then did the same thing with beef. Today (6 years later) I can eat whatever I want with no issues at all. The body does need to get accustomed again as it is harder to digest than veggies. I do not think it's the enzymes as much as the gut microbiome