Flatulence or gas can be annoying and embarrassing, but it's something that just about everyone has experienced to varying degrees. The good news is that you don't have to endure it, well at least not all the time.

What Causes Gas?

The first step toward lessening gas is learning what causes it. Most intestinal gas in healthy people results from bacterial fermentation in the colon, says gastroenterologist Satish SC Rao, MD. Complex carbohydrates are the cause of the rectal gas we pass. These include certain sugars, starch, and fiber .

"A normal diet contains a lot of carbohydrates that aren't digested by small bowel enzymes. Instead, they are dumped into the colon," Dr. Rao explains. "Between 15 and 30 grams of carbohydrates are dumped into the colon everyday, where they're digested by bacteria." This fermentation by bacteria gives off gas.


The meanest gas-producing carbohydrates, raffinose and stachyose, are found in beans. These include kidney beans, lima beans, black beans, navy beans, and soybeans. A 1999 study in The American Journal of Clinical Nutrition compared a specially made DuPont soybean (low in gas-producing carbohydrates) with the conventional soybean. People who ate the DuPont invention experienced less gas.

Milk Sugar

Lactose, which is found mostly in milk and dairy products, can also cause excess gas in some people. People who don't have enough of the enzyme lactase, which digests lactose, experience gas. This condition, known as lactose intolerance, is much more common among people of Asian, Native American, and African decent, than among people of European decent.

Other Sugars

The sugars fructose and sorbitol are also gas producers of the carbohydrate clan. Fructose is found in many fruits and vegetables. Sorbitol is found in fruits, including apples, peaches, and pears. Sorbitol is an artificial sweetener commonly used in sugar-free food products and candy.

Starches and Fiber

Aside from sugars, starch and fiber camp out in the colon too. Starches include potatoes, pasta, and rice. (Rice is fortunately fart-free). Soluble fiber found in oat bran, beans, peas, and most fruits can also give off gas.

Swallowing Air

You probably knew that eating food causes gas, but what about eating air?

"Air swallowing is one of the most common causes of gas, and it can be caused by eating quickly and taking in large amounts of air," says dietitian Lisa Andrews, MEd, RD.

But swallowed air primarily escapes through belching, not through the rectum, says Dr. Rao.

Air swallowing can also be completely unrelated to eating. Other causes of swallowed air, according to gastroenterologists and dietitians, include the following:

  • Anxiety
  • Smoking
  • Chewing gum
  • Loose dentures
  • Drinking carbonated beverages
  • Drinking through straws

What Makes Gas Smell?

Of all the gas we pass, researchers estimate that less than 1% smells. Odorless gas consists of nitrogen, oxygen, hydrogen, methane, and carbon dioxide. Researchers suspect that odorous gas consists of sulfur.

What Is a Normal Amount of Gas?

The average person passes gas eight to 14 times a day. In fact, passing gas less than 25 times a day is normal, says Dr. Rao. (Of course, it could be worse. We could be bovines. One cow produces 14 cubic feet of methane per day.)

How to Reduce Gas

Andrews recommends taking these five steps towards freedom from flatulence:

1. Avoid gas-producing foods at inconvenient times
"Remember that many of these foods are very healthy," says Andrews, "so don't completely eliminate them from your diet."

2. Introduce fiber slowly
But don't reduce it, says Andrews. "I wouldn't recommend a lower fiber diet, because fiber has so many health benefits," she says.

Instead, Andrews recommends gradually introducing fruits, vegetables, and whole grains to your diet. You may want to start off eating one or two fruits and vegetables a day for a week, she says. You should then up your fiber intake to five servings of fruits and vegetables a day over the next week or so. Remember to drink at least six to eight glasses of water a day to help prevent constipation.

3. Take Beano and other over-the-counter medications
Beano is an enzyme that is available over-the-counter in the form of drops or tablets at most major drugstores and grocery stores. It helps break down certain starches and relieves gas from beans and from vegetables with raffinose and stachyose.

In one study, people who took Beano passed slightly less gas after eating beans, but they all experienced the same amount of pain and bloating. Activated charcoal tablets, such as Charcocaps, may also relieve gas, according to some, but not all, research. Medications that contain the enzyme lactase, such as Lactaid, may also provide relief but only from lactose-induced gas.

4. Have some bacteria
Friendly bacteria, such as Lactobacillus acidophilus, may reduce gas. Start with a small dose and build up.

Should I See a Doctor For My Gas?

If after trying all these tips, you still experience excessive gas (25 or more episodes a day), see your doctor. Although gas is a normal part of life, it can also be a sign of an important but treatable gastrointestinal illness.