Some people find gas—and the belching (burping), flatulence, and stomach bloating that go with it—an embarrassing subject, but it’s actually a normal occurrence. In fact, the human body produces between one and four pints of gas a day, which it releases via the mouth or the rectum about 14 times a day.
Where does gas come from?
Gas gets into the digestive tract when you swallow air (oxygen) and during the normal metabolism of carbohydrates. Here's how it works:
Swallowed air. You swallow small amounts of air when you’re eating and drinking, and you take in greater amounts when you eat or drink rapidly, don’t chew your food completely, suck on hard candies, chew gum, smoke cigarettes, or wear loose dentures. Most swallowed air escapes from the stomach via the mouth when you burp, or belch. The rest of the air travels to the small intestine; some of it is absorbed there, while the remainder moves into the large intestine and then is released through the rectum.
Neutralization of acid. When acid is secreted by the stomach, it reacts with chemicals in the food that we eat to produce carbon dioxide gas. Much of this is burped up, but some can travel downstream to produce bloating and distention.
Undigested carbohydrates. Gas is also produced by bacteria in the colon when carbohydrates are not digested in the small intestine. Most carbohydrates can be broken down and absorbed in the small intestine, but some—like fiber—cannot be digested. Other carbohydrates that normally can be absorbed—like lactose (milk sugar)—are unable to be digested in some people because of a lack of enzymes.
When a carbohydrate enters the colon, the normal bacteria, which are harmless, ferment it and produce the odorless gases hydrogen, carbon dioxide, and sometimes methane. The bacteria may also release malodorous gases containing sulfur. Like stool, the gases are then passed out of the body through the rectum. Until they are passed, the gases that are formed may cause abdominal bloating or even discomfort.
Foods that cause gas
Several types of carbohydrate-containing foods are notorious for causing gas. These foods include:
• Vegetables such as artichokes, asparagus, broccoli, Brussels sprouts, cabbage, corn, onions, and potatoes
• Fruits such as apples, peaches, and pears
• Beans (especially baked beans)
• Carbonated beverages
• Wheat products such as pasta and whole grain breads and cereals
Many people also develop gas after consuming milk products that contain the sugar lactose. This is because they make insufficient amounts of the enzyme lactase, which the body needs to digest lactose. As you age, your lactase level naturally declines. Fats and proteins rarely cause gas.
When to call a doctor
Most cases of gas are normal. But an unusual amount of gas (more than 23 episodes of flatulence or belching/burping a day on a regular basis) or symptoms like abdominal bloating and discomfort may indicate lactose intolerance or a more serious disorder. If this is the case, you should make an appointment with your doctor.
Chronic belching can be a sign of gastroesophageal reflux disease (GERD) or a peptic ulcer, while stomach bloating can be a sign of irritable bowel syndrome (IBS), gastroparesis (delayed emptying of the stomach), or Crohn’s disease.
People who’ve had hernias in their digestive tract, have undergone many surgeries to their digestive tract, or have scar tissue in their digestive tract may also have problems with bloating and pain.
From a review of your diet and the number of times you pass gas a day, a doctor can often determine the cause of your symptoms. If a diagnosis is not obvious (for example, excess gas is not related to lactose intolerance or consumption of a large amount of gas-causing foods), your doctor may suggest you have a sigmoidoscopy, colonoscopy, or upper GI series to determine if you have a serious disorder.
What to do about flatulence, burping, and bloating
Here are some easy steps you can take to reduce the amount of gas you pass:
• Eat and drink slowly and chew your food well. This will help reduce the amount of air that you swallow.
• If you’re prone to gas, avoid chewing on gum and sucking on hard candies. Be aware that sugarless gum and candies containing the poorly absorbed sweeteners sorbitol, xylitol, or other sugar alcohols can cause or contribute to flatulence and diarrhea.
• If you have dentures, check with your dentist to make sure they fit properly.
• Identify the foods that cause gas for you. In most cases, there is a lag of two to three hours between ingestion and gas production to allow for carbohydrates to reach the colon. You probably won’t need to avoid these foods altogether. Instead, you’ll just have to reduce the amounts you currently eat.
So experiment to find out how much of these gas-causing foods your body can handle before gas becomes a problem. Your doctor may give you a hydrogen breath test, which can confirm a link between symptoms and specific foods.
• If you’re adding fiber (more fruits, vegetables, and whole grains) to your diet, do so slowly so your body can adjust without producing excess gas.
• If you experience gas after eating dairy products, you can take lactase supplements (Lactaid, Lactrase) while eating to reduce how much gas your body produces. You can also buy lactose-free milk and other products, such as Lactaid and Dairy Ease.
• Try the over-the-counter digestive aid, Beano, which contains an enzyme that helps you to digest the sugar in beans and vegetables when you eat these foods. You can add Beano to your food as a liquid or take tablets before eating.
• Try taking bismuth subsalicylate (Pepto-Bismol) or chlorophyll tablets to reduce the odor of gas.
• Peppermint oil may reduce discomfort from bloating in some people.
• Engage in regular physical activity (30 minutes a day on most, and preferably all, days of the week). Doing so will help speed the clearance of excess gas.
• Strengthen your abdominal muscles by pulling in your stomach several times a day, regularly doing exercises such as sit-ups, or wearing a support garment. Strengthening your abdominal muscles will also help decrease bloating.
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