Belching, burps, farts and flatulence. How to deal with gas in the digestive tract.

Here’s a fact: everyone has gas – from the starchiest friend to the most elegant celebrity.  Lots of people think they have too much but usually they have normal amounts.  And what are normal amounts?  Most people pass about 1-4 pints each day and pass gas up to about 20 times a day either through burping or passing flatus – farting (source National Digestive Diseases Information Clearinghouse, a service of National Institutes for Health (NIH)).

In this article we’ll look at why the gas is formed and what you can do about reducing its amount if you feel you’re passing excessive quantities.

What is digestive gas?

You can see from the diagram here that the digestive system is a long tube, starting at the mouth and ending at the anus.  The job of the digestive tube is to:

  1. crush your food
  2. mulch it down to a pulp
  3. remove the nutrients – vitamins, minerals, protein, fat and carbohydrate
  4. reabsorb fluid
  5. get the remaining solids (faeces/poop/poo) ready for expulsion via the anus.

During this process, which can take up to 24 hours, the breakdown products of some foods produce gas.  Gas in the stomach is often released as burping/belching.  Gas in the lower digestive tract is released as farting.  Both can be uncomfortable, embarrassing and smelly, depending on what you’ve eaten.

Gas is mainly made up of carbon dioxide (CO2), oxygen, nitrogen, hydrogen and sometimes methane, all of which are odourless.  The characteristically unpleasant smell of gas from the lower digestive tract is from the bacteria which are breaking down the food in the large intestine, as they release some gases containing sulphur.

What causes digestive gas?

Gas comes from 2 sources – swallowed air, and the normal breakdown of foods as we discussed above.

  1. Swallowed air (doctors call this aerophagia – say ‘air-o-fayjia’) mainly causes gas in the stomach and consequent burping.  It happens:
  • When you’re eating or drinking, especially if you’re eating/drinking quickly or drinking carbonated beverages.
  • When you chew gum.
  • Some people have a nervous habit of unconsciously swallowing air when they’re anxious.
  • Excessive belching can be caused by gastroesophageal reflux disease (GERD/GORD)
  • It can also be caused by delayed gastric emptying – gastric paresis.  This can happen as part of migraine or for another reason.
  • It can also come from certain foods and beverages – see below.

This swallowed air can cause an uncomfortable feeling of bloating and fullness in the stomach.  You may have pain until it’s released by a burp, as well as the embarrassment of the burp.

How to reduce burping and belching.

  • Avoid chewing gum if you find that makes you burp.
  • Avoid carbonated beverages such as sodas and fizzy water.
  • Eat slowly and try not to talk when you eat.
  • Stop smoking.
  • If you wear dentures make sure they fit correctly.
  • If you have excessive heartburn and gas then talk to your doctor about a test for GERD/GORD.
  • Some dieticians suggest that reducing your intake of fatty foods.  This is said to help to reduce bloating and make the stomach empty more quickly, moving the food (and gas) into the small intestine.
  1. Breakdown of undigested food.

Foods cause varying amounts of gas to be released as they are digested.  Proteins and fats cause small amounts of gas but carbohydrates cause more.  Carbohydrates are mainly digested in the large bowel because this is where there are the right bacteria and enzymes are situated.

Carbohydrates are broken down to sugars, which are their basic elements, and the body uses these sugars as its fuel/energy.  However there are some sugars that can cause more gas than others.  These are: fructose, raffinose, lactose and sorbitol.

Fructose is a sugar found in fruit and also onions, wheat and artichokes.  It is also used as a sweetener in fruit drinks and soft drinks.

Raffinose is found in cabbage, Brussels sprouts, broccoli, beans and whole grains.

Lactose is a natural milk sugar so it’s found in milk and milk products (cheese, cream, ice cream etc).  The enzyme which digests lactose is called lactase and if this enzyme is at a low level the body may produce more gas as it can’t properly digest lactose.  Some people have a low level of lactase, especially after childhood, and its level decreases as we get older.

Sorbitol is also found in many fruits and is used as an artificial sweetener in low sugar foods and diabetic foods.

Starches produce gas as they are digested.  Starches are carbohydrates in potatoes, corn, and wheat.  The only starch not to produce gas when it’s broken down is rice.

Fibre in the diet is of 2 varieties – soluble fibre and insoluble fibre.  Insoluble fibre is found in foods like wheat bran and is good for helping the bowel work normally, especially if you suffer from constipation.  It produces very little gas.

Soluble fibre is found in oatbran, beans, vegetables and fruit.  It dissolves as part of the digestive process and can cause gas in the large intestine.  Soluble fibre is important in the diet, especially if you have high cholesterol as it can help reduce this.

How to reduce gas in the large bowel.

The amount of gas caused by some foods will vary from person to person.  Something that causes a problem for one won’t be a problem for another because of the way the gut processes the gas as well as the foods.

Reducing the amount of fruit, vegetables and milk products you eat may help the gas but may cause broader problems for your health as they are healthy foods.

  • Keep a food diary and think about which foods seem to cause you the most problems.  And record your emotional state as conditions such as irritable bowel syndrome (IBS) can have a stress-related component to them.
  • Over-the-counter meds for gas include digestive enzymes which help you digest carbohydrates.
  • Examples of these supplements are: lactase (Lactrase and Lactaid) which helps you digest milk; Beano helps the body digest the sugars in beans and other vegetables.

Should I be worried about gas?

Generally no.  We all produce gas and politely burp behind our hands or blame the dog for farting.

As we mentioned above, excessive belching can be related to GERD (gastroesophageal reflux disease) where the stomach is producing too much of its digestive acids.  This can cause ulcers in the upper digestive system so should be identified and treated by your doctor.

Abdominal pain and bloating is often a symptom of an intestinal problem such as irritable bowel syndrome, Crohn’s Disease, intestinal obstruction or inflammation or colon cancer.  People who have had an operation on the bowel or for a hernia can experience pain and bloating from adhesions where scar tissue has formed after the op.

If you are worried about your symptoms of gas, pain or bloating then see your doctor.  It would be worth keeping a food diary for a few weeks before your appointment.  Record:

  1. What you eat, including snacks, drinks and food between meals
  2. When you eat and what you’re doing when you eat – watching TV, talking with friends etc.
  3. When the gas/bloating/pain happens in relation to when you eat
  4. What relieves the symptoms
  5. How long the symptoms last
  6. Other bowel symptoms such as constipation, diarrhoea, nausea, vomiting, blood in the stools or on the paper when you wipe after a bowel motion (in which case see your doctor sooner rather than later)
  7. Other life and emotional stresses etc
  8. How long these other symptoms have been going on for.

All this information will be like gold dust for your doctor in helping you both to get to a diagnosis and treatment sooner.

For further info also look at, the website for the International Foundation for Functional Gastrointestinal Disorders, and the website for National Digestive Diseases Information Clearinghouse.

If you’re worried about your symptoms or medical problem but don’t want to seek professional help because you feel embarrassed, silly or that it’s your fault, read this page now:  How to talk to a doctor about an embarrassing problem.

Elspeth Raisbeck

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