What makes us fart?

The answer may stink, but eating or drinking anything gives us gas. In fact, it's normal to fart up to half of a gallon (1.9 liters), or about 15 to 20 toots worth of gas, each day.

When we gulp down food, air comes with it. So if a belch seems rude, remember that the air has to leave our bodies one way or another.

Fragrant flatulence, however, comes from colonies of bacteria shacked up inside our lower intestinal tract (which is why it can take hours for gas to kick in after a meal). In the process of converting our meals into useful nutrients, these food-munching microbes produce a smelly by-product of hydrogen sulfide gas—the same stench that emanates from rotten eggs.

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