The main culprit isn't the sugar or the caffeine—it's the bubbles. Carbonated beverages are infused with carbon dioxide gas, which gives them that signature pop and sizzle.
When you drink a soda, you swallow a significant amount of that gas. The average can contains about 2.2 to 2.5 volumes of CO2, meaning a 12-ounce can holds roughly 30 ounces of gas. Your stomach can handle some, but the excess has to go somewhere.
Some of the gas escapes upwards as a belch, but the rest travels down into your intestines. There, it mixes with other gases produced by your gut bacteria, creating a pressure cooker of air that eventually needs an exit strategy.
Sugar, Fructose, and the Gut Microbiome
Here’s where the plot thickens. It’s not just the gas you swallow—it’s what the sugar does once it arrives. Many popular pops are loaded with high-fructose corn syrup or sucrose.
Your small intestine can only absorb so much sugar at once. The undigested fructose then takes a trip to your large intestine, where your resident gut bacteria throw a party. They ferment that sugar, producing hydrogen, methane, and (in some unlucky people) sulfur—the stuff that gives gas its distinctive aroma.
This is why diet soda can sometimes be even more gassy for some people. Artificial sweeteners like sorbitol and aspartame are notoriously difficult for the gut to break down, leading to bacterial fermentation that creates extra gas volume.
The 16 foods most likely to make you fart - and how to stop your smelly
