Lactose intolerance.
Did you know 90% of people with Asian lineage cannot drink cow’s milk without losing a day to intestinal upset? That is correct. 90%. Look it up.
If you are not Asian, but are older, you become more lactose intolerant. You can do a search for cheeses that have more or less lactose.
There is more to the dairy thing than bacteria.
Raw milk is often better tolerated. It’s pasteurized milk that lacks the lactase for lactose digestions.
https://www.rawmilkinstitute.org/updates/raw-milk-and-lactose-intolerance
At 71, never had a problem, thank God.