Cinnamon bark is used for gastrointestinal (GI) upset, diarrhea, and gas. It is also used for stimulating appetite; for infections caused by bacteria and parasitic worms; and for menstrual cramps, the common cold, and the flu (influenza).The oils found in cinnamon bark are thought to reduce spasms, reduce gas (flatulence), and stimulate the appetite. Cinnamon might also increase blood flow. Cinnamon bark also contains a chemical that might work like insulin to lower blood sugar. However, these effects are thought to be fairly weak.