Feeling bloated, crampy, or just not yourself? It might be IBS—not just stress or food intolerance, but a complex gut issue.

Austin Chiang: "Your stomach shrinks if you eat less." Is that true? Fola May: Myth! May: "Jumping or exercising after eating will give you an appendicitis." Chiang: What? I have never heard of this.

They may help prevent diarrhea and ease symptoms of IBS, but experts don't yet know which ones help or how much you should take. And that's the dirt on bacteria.