"Beans, beans, the musical fruit; the more you eat, the more you toot." Beans may have a reputation as a "musical fruit," but for all their noisiness, they don't usually make farts smell worse. The same is true for most flatulence-causing foods, such as asparagus or chickpeas; they may make you fart more often, but they don't make your farts particularly stinky.
Sure, a vegetarian's diet — based on fruits, nuts, vegetables and legumes — is rich in fiber, but fiber alone isn't to blame for the increased gas production that comes with plant-based eating habits. The culprit is actually a type of sugar molecule called oligosaccharides. Oligosaccharides are too large to be easily absorbed through the wall of the small intestine, so they move through the large intestines unfettered — until they meet some of the 70-plus kinds of bacteria that live there. As these bacteria feast on oligosaccharides, they create an abundance of gassy byproducts colloquially known as farts [source: Soniak].
While the jury's still out on whether vegetarians fart more often than omnivores, there is evidence that vegetarian farts may be among the least noxious. Or not as noxious as a meat-eater's farts, anyway.
The credit for smelly farts goes, in part, to meat that is consumed as part of an omnivore's diet. For the most part, meat contains high levels of sulfur, and sulfur-laden foods produce more odors as they are digested. When bacteria in the digestive system break down foods, it produces byproducts. When they breakdown foods rich in sulfur, the byproducts include sulfides and mercaptans, the gases that lend their unmistakable smell to farts. Hydrogen sulfide, in particular, causes passed gas to have an odor reminiscent of rotten eggs. The other gases produced during digestion — nitrogen, carbon dioxide, oxygen and methane — are virtually odorless [source: Levine].
By contrast, most vegetables produce fewer smelly byproducts during digestion, like hydrogen sulfide, than meat.
But don't think that just because you don't eat meat, you'll never have smelly farts. Any food that is high in sulphites, such as cabbage, broccoli, onions, Brussels sprouts, peas, leeks and garlic will result in sulfide- and mercaptan-rich gas production. So, even though omnivores and vegetarians may not have much in common when it comes to selecting a main dish off the menu, they can raise their forks in unity at the wonders of gut bacteria. Regardless of what we eat, we all fart. And sometimes, it's smellier because of what we've eaten.