I have always been told that you shouldn't drink milk and eat yoghurt together. So today in the kitchen channel when they made a smoothie with milk and yoghurt I was shocked. Since I couldn't find information online, I ask here: is it safe to drink milk and yoghurt together?
Yes, that’s perfectly safe.
If your yogurt has live yogurt bacteria (so not pasteurized after fermentation), some of that bacteria would turn the fresh milk into yogurt if given enough time - but we are talking about hours in a rather warm environment, not in a smoothie that is mixed and then consumed rather quickly or stored in the fridge.
The milk is just to thin the smoothie without watering it down or the yogurt to add a bit of acidity without curdling the milk.