This time on A Moment of Science, we discuss a rather delicate subject--gas (and we don't mean the kind you put in your car).

It's normal and healthy to let out a little belch here and there after a meal. It's just one of the ways the body gets rid of gas. You probably know that we produce gas from foods like beans. Many foods high in carbohydrates, meaning sugars, starches, and fiber, have to be broken down in the large intestine by certain bacteria present there. These bacteria help our bodies digest, but in the process they produce hydrogen, carbon dioxide, and in some people, methane. This gas is passed through the rectum.

In addition to food breakdown, we also accumulate gas in the stomach by swallowing air when we eat and drink. Though some of this swallowed air travels into the intestines, most swallowed air is belched out before it gets that far.

On top of belching, it is normal for a person to pass gas 14 to 23 times a day. That amounts to 1 to 3 pints a day per person. As far as belching is concerned, people who belch a good deal more frequently than others after meals might be swallowing too much air. They should try to cut down on the chewing gum and eat slower.