I feel two ways about yogurt. On the one hand, there "friendly" pro-biotic flora are present...but on the other hand, it IS dairy which produces acid. And most yogurts do contain preservatives and sugars.

However, where I live in Macedonia, yogurt is made at home by boiling milk, setting it to cool, adding a yogurt culture and then sticking it under the bed for a night. Hundreds of years of dietary use can't be wrong!