Science Questions

I learnt in school many years ago that food takes 12 to 24 hours to travel through the body. As I've got older, out-gassing has become a more noteworthy part of my life but it doesn't appear to adhere tot his time schedule. When I eat flatulent foods such as beans or something like that, I become very gassy in a little as one to two hours. Why is this? Where in our gut do these vapours form and how do they get out so quickly? Dan in New York

The average human produces between half and one and a half litres of flatulent gas every day. This is partly oxygen and nitrogen that we've swallowed when we eat. But partly it's things like gases that are produced by microbes in our guts. We know that bacteria make these gases. Food passes from your mouth into your stomach and then into your small intestine within about one to two hours of eating it. It then takes five or six hours to get through your small intestine and then twelve to twenty four hours to get through your large intestine and colon. Most of the bacteria that make these smelly gases hang out in your colon, but some especially gassy people have a lot more of these bacteria in their small intestines further up the intestinal tract. This is probably what Dan is finding. The bacteria are getting to work on the food much quicker and so he's probably finding that he's getting gas much quicker than other people.

May 2006