What causes a person to have gas?
According to WebMD, drinking through a straw, eating or drinking too fast, smoking and chewing gum all increase the amount of swallowed air in a person’s digestive tract. Carbonated sodas increase the gas inside the body due to the chemical process that causes the bubbles. Some individuals who suffer acid reflux swallow air to force the acid back into the stomach. For others, swallowing is a nervous habit that increases the gas in the digestive system.
Sources: digestive.niddk.nih.gov, webmd.com, mayoclinic.org