The fulfillment that comes with eating a hearty meal is one of the great joys in life. After a good meal, we feel not only fuller, but more ready to face the world. Combined with the company of good friends or family, such a meal produces happiness unlike any other.

However, there are evil forces at work in the universe that would deprive us of this happiness. These nefarious forces do not show themselves immediately after the meal. Rather, they give the eater a taste of post-feast contentment that makes the subsequent eruption all the more distressing. The offenders make themselves known first with a rumble in the gut, which is almost immediately followed by a loud burst that scientists like to call "flatulence."

What are these demons in our bellies called, you ask? What molecules would be so bold as to deny us our after-dinner enjoyment?

They go by many names — lactose, inulin, oligosaccharides — but as a group, they are referred to as the "indigestible carbohydrates." Instead of being digested in the small intestine like good little carbohydrates, these tiny devils move into the colon unaltered. There, they are eaten by bacteria that produce massive volumes of gas (and, for fellow diners, discontent). In fact, the chemistry blog Molecule of the Day (http://scienceblogs.com/moleculeoftheday) recently reported that just 1 gram of carbohydrate can produce 700 milliliters of gas! That's enough for roughly seven after-dinner, ahem, interruptions.

The first of the molecules I mentioned, lactose, is the most benign. In fact, most Americans can digest lactose, which is the principal sugar found in milk. For the majority of the population, this sugar is broken down by the enzyme lactase in the small intestine. However, some individuals, particularly those who trace their ethnic heritage back to countries with traditionally low milk consumption, do not produce lactase. After consuming large amounts of lactose, these folks develop serious cases of flatulence, but artificial lactase and lactose-free alternative products allow them to minimize their gas production. Furthermore, even most lactose-intolerant people can handle a cup of milk per day without too many adverse effects. Lactose is a relatively tame foe when compared to the other indigestible carbohydrates.

A greater and more universal offender than lactose is inulin, a form of fiber that exists in plants such as onions, garlic and Jerusalem artichokes. In fact, the last of these is reputed to wreak such havoc on digestion that the 17th century English botanist John Gerard once remarked of them, "Which way soeuer they be drest and eaten they stirre and cause a filthie loathsome stinking winde within the bodie, thereby causing the belly to be pained and tormented and are a meat more fit for swine than men." Delicious!

The last of our unholy trinity of indigestible carbohydrates are perhaps the most malicious of all: the oligosaccharides. These three-, four- and five-sugar carbohydrates have long been considered the reason beans are referred to as "the musical fruit," and they are scientifically proven to produce toots. However, recent research — yes, there are people who research this kind of thing — suggests that cell-wall cements also play a role in gas production from beans. Either way, the indigestible carbohydrates in beans make them the composers of many a sad chord in the soundtracks of our lives.

It is tempting to submit to the collective will of these indigestible carbohydrates, to throw our hands in the air and let our gut bacteria do their dirty work. However, thanks to modern chemistry, we can enjoy indigestible carbohydrates without unwanted gas production. For lactose-intolerant folks suffering after a glass of milk, it's as simple as ingesting some lactase with their beverage. In the cases of other indigestible carbohydrates, however, people who want to eat massive quantities of Jerusalem artichokes or three-bean chili need the help of something the body does not normally produce — alpha-galactosidase. This enzyme, which is sold over the counter as Beano, breaks down the normally indigestible carbohydrates, making them cave to the digestive power of the small intestine. Because of chemistry, we need not cave to the gassy forces of evil.

Indigestible carbohydrates are a powerful force. They bring with them loud noises and potent smells, and it is probably a good idea to resist them. However, in using chemicals to treat the symptoms of eating, say, a black bean quesadilla, it is important that we not forget the food's traditional effects. Perhaps the person who best sums it up is 16th-century Christian reformer Martin Luther, who was no stranger to indigestible carbohydrates. After serving dinner to a houseguest, he supposedly once asked, "Why do you not belch and fart? Did you not enjoy the meal?"

Jason Engelhart is a junior majoring in economics and history. Post-dinner intestinal turmoil getting you down? Let Jason know. E-mail him at [email protected]