If you're going to hang around this blog, you need to know that we cook with a lot of Greek yogurt. It is our one dairy exception because it doesn't negatively impact my husband. Lactose intolerance is caused by milk sugars -- they are the culprit. The active cultures in Greek yogurt eat the milk sugars. Therefore, most people with a lactose intolerance problem, my husband included, are able to eat Greek yogurt.
Whenever a recipe calls for sour cream, heavy cream, evaporated milk, etc., or when we want sour cream as a dip or topping, we substitute plain Greek yogurt.
There you have it. I hope we're still friends.
Disclaimer: I am not a nutritionist, nor is my husband. Through trial and error we discovered that Greek yogurt does not have the same negative effect as other dairy. The analysis above is one I arrived at through my own research and is not scientifically proven. Please incorporate at your own risk.