Maybe you don't want to buy buttermilk for a recipe that calls for just half a cup of it, or maybe you've already started cooking and just realized you need buttermilk and don't have any. Nothing matches the pure taste of buttermilk exactly, and if you really want to taste that flavor—if you're making dip perhaps—you should try and stick with the real thing. But if you're baking or making pancakes, don't worry about using a substitute.

The reason a lot of baking recipes use buttermilk has to do with the chemical reaction between baking soda and lactic acids. Remember making volcanoes in elementary school science class? The first time I saw that as a kid it seemed like magic: pour vinegar over baking soda and lots of bubbles pour out over the top of the vessel. Similarly (though not as dramatically) when baking soda and acidified dairy are combined in a batter, they release Co2 bubbles that help leaven and lighten whatever you're making—real, grown-up, baking magic! That magic works just as well with any of these substitutions.