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Digestive System

Why can humans not digest corn?


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August 27, 2014 3:41PM

Most of us have probably realized that after eating corn, it shows up in our stool. The corn in our stool can appear only hours after we eat it. Rest assured, corn in the stool is normal, and the reason we see the corn relates largely to our digestive tract, and also to evolution.

Millions of years ago, our digestive systems were different. Primitive man was not a big meat eater. Primitive man had a digestive system with a longer digestive tract that was far better equipped to digest plant and vegetable matter. Back then, the appendix likely played a role in digestion -- a role it does not play today.

Our teeth were different then, too. We had larger molars and smaller incisors. Larger molars meant that the difficult-to-digest plant material could be well chewed and mashed. Today, our teeth are smaller and many of us even have problems with our wisdom teeth (our largest molars), which are being phased out by evolution because our diets today really do not require them. (Our jaws are becoming smaller, and as a result the wisdom teeth have less room to grow in.)

So how does this all relate to corn, and why it is seen in the stool? Since we have smaller teeth, we chew our food less effectively, and more of what we eat is swallowed only partially chewed, or not chewed at all. With corn, some of the kernels will be chewed fully, some partially, and the others will be unchewed and swallowed whole. Our digestive system today is not that good at digesting plant material anymore, much less whole kernels. They pass through our stomach and intestines, and appear in our stool to confound and entertain us.

If you would rather not see any corn in your stool, I recommend that you just chew each mouthful into a mushy mixture free of any whole kernels.

One last point I want to make is that it is not difficult for our digestive systems to pass corn kernels. It is really amazing what the digestive system can tolerate and pass. Drugs are frequently smuggled into the country by individuals who swallow balloons or condoms filled with the drugs. (These people are called "body packers.") In addition, I have read on several occasions about people who unintentionally swallowed their dentures, only to pass the dentures in their stool a few days later. I have also read of children swallowing thermometers passing them just the same.

The human digestive system really is fascinating. But remember that we are slowly evolving over time -- our digestive systems are constantly adapting to our diets and our environments. Our digestive systems of today will not be the same as the digestive systems of humans thousands of years from now. Remember this the next time you enjoy your corn, or broccoli, or any other difficult-to-digest food product -- what kind of food might future generations be spotting in their poop?