How does your body digest food?

By Marshall Brain

In the video, we first used things like sponges and rope to show what the digestion organs (stomach, large intestine, small intestine) look like inside your body. A sponge makes a good model for the stomach, a 20-foot long piece of rope makes a good model for the small intestine and then we used pipe insulation for the large intestine and the throat (a piece of thicker rope would work just as well. Handing those kinds of things to your child, having him/her lie down on a couch and then having him/her show you what is inside his/her abdomen can be a good exercise.

The video also suggests an experiment to try at home. It sounds a little gross, but by talking about it you can get past the grossness. It is a fun experiment for the whole family to try, and it is very simple. All you have to do is eat some corn.

The thing about corn is that it has a nice, bright yellow color and the human digestive system is not able to digest all parts of a corn kernel. This means that you can use corn as a "marker" and track its progress through the digestive system. Simply eat some corn (a quarter-cup or half-cup would be plenty) and then time how long it takes for the corn to come out. The times will be different for different family members.

There are all sorts of variations that you can try. For example, if you are eating a lot of meat and processed foods when you eat the corn, how long does it take to come out? Now switch your diet to lots of fruits, veggies and salads. Does the time change? Does it matter if you eat the corn in the morning or the evening? You could perform many experiments over the course of several weeks and come up with average times as well as special situations.

An obvious question to ask is, "why doesn't the human digestive system completely digest corn?" As you are doing these experiments, you may also notice that it can't digest lettuce very well either. It is because the human digestive track does not contain the enzymes we would need to break down long carbohydrate chains found in things like cellulose. We would not be able to digest grass either, but animals like cows, goats and sheep digest grass without any problem. Termites are able to digest wood. Different digestive systems are able to handle different foods.

Finally, the video talks about farting (flatulence). There is a huge colony of bacteria living in your large intestine. If food passes through the small intestine without being digested, and if these bacteria can digest it, the bacteria will produce gas (just like yeast do). That gas becomes a fart. Beans are one food that causes flatulence for many people. Raisins are another. Are there foods that make you flatulent?

Have fun performing your own science experiments!