Olives clearly have a few things going for them. But they’re not all created equal, which makes answering the question Are olives healthy? a little complicated.

See, the curing process involves sodium—sometimes a lot of sodium—so if you’re trying to limit your intake, Brynn McDowell recommends buying olives in a jar, which will have a nutrition label outlining exactly how much sodium is inside. “The self-serve olives at the vegetable bar in most grocery stores don’t always have that information available,” Brynn says. And that means you could be on the fast track to a sodium hangover without even realizing it.