The best smoothies are made with buttermilk...

I was raised on it, so I am partial to it, but my daughters still can't stand the stuff, unless I fool em by making strawberry/banana smoothies with it, then they love the stuff.

I was informed that the worst of the three for palatability is definitely the raw sourdough starter. That's gauranteed to take your mind off your other worries and make you squint your eyes shut.