Everyone has a certain amount of gas in the gut. Some people, however, are sensitive to normal amounts. They experience pain, burp excessively or pass large amounts of wind as the gas passes through the gut.
Occasionally, greater than normal amounts of gas are produced. There are several situations in which this may occur, including air swallowing, dietary factors and, less commonly, bowel diseases.
Changes to the diet, various medicines and products which deodorise gas may be helpful.
What is trapped wind?
There is always a certain amount of gas in the bowel. Most of this comes from air swallowed whilst you eat or drink. It can also happen during smoking or when swallowing saliva. Larger amounts can be swallowed when you eat quickly, gulp down a drink or chew gum. The swallowed air goes down into the gullet (the oesophagus).
If you are sitting up, the air tends to go back up the oesophagus and escapes again through the mouth in the process of belching. If you are lying flat, the air tends to pass downwards causing gas in the stomach. This can result in bloating after eating and a hard, swollen tummy. The gas eventually enters the small bowel (small intestine) and escapes through the back passage (anus). People often refer to this as 'farting' or, more politely, 'passing wind'/'passing gas', or flatulence.
Gas can also be produced due to germs (bacteria) acting on partially digested food in the gut. This is more likely to happen with some foods than others. Broccoli, baked beans and Brussels sprouts are well-known culprits. The number of germs in the bowel also has an effect on the volume of gas produced. The gas that is made is mainly composed of carbon dioxide, hydrogen and methane. It may contain traces of a chemical called sulphur. This is responsible for the unpleasant smell experienced when you pass wind through the back passage.
Abdominal bloating is the term used when the tummy feels blown out, tight or full of gas. It results in a swollen stomach and the waistband of a skirt or a pair of trousers may feel uncomfortable. You may experience crampy tummy pains.
Trapped wind symptoms
Symptoms of trapped wind and bloating include:
- Passing a lot of wind.
- Crampy stomach pains.
- Bloated belly.
- Pain in upper abdomen
Gas sometimes settles in the curves of the large bowel (large intestine) under the liver or spleen. This can cause pain in the upper right or upper left areas of your tummy.
Most people who are bothered by these types of symptoms do not actually produce more gas than usual, they are just more sensitive to normal amounts. However, it is now considered that some patients with irritable bowel syndrome do produce larger than normal volumes of gas. Irritable bowel syndrome is a condition in which bouts of tummy pain are associated with bloating and changes in bowel habit such as constipation and diarrhoea. See the separate leaflet called Irritable Bowel Syndrome.
Just to complicate matters further, the amount of bloating does not relate to the seriousness of the cause. People with irritable bowel syndrome may complain of severe bloating, whilst in those with coeliac disease the bloating may be mild, moderate or severe.
What causes trapped wind?
Everybody has trapped wind symptoms from time to time. In most cases, this is part of the natural working of the body and the symptoms soon pass. Some people complain they are feeling bloated all the time. As mentioned above, people are occasionally sensitive to normal amounts of gas in the tummy. The reasons for this are not entirely clear.
There are some conditions associated with larger than normal amounts of gas in the tummy:
Swallowing too much air
This is called aerophagia. You may not be aware of it but you may be swallowing air frequently or in large amounts. This often happens in people who are under stress. It can be aggravated by chewing gum and smoking. Usually, air swallowed in this way passes into the gullet (oesophagus) and down into the stomach.
However, sometimes air is sucked into the back of the throat (the pharynx) and is burped out before it reaches the oesophagus. This is known as supragastric belching.
Some people swallow air deliberately to cause belching, as they find this helps to relieve symptoms of indigestion.
Foods which are well known to cause excessive wind in the gut include:
- Brussels sprouts.
- Starchy foods such as potatoes, corn and noodles.
- Foods high in soluble fibre (eg, fruit, peas and beans).
Lactose intolerance happens when your body has difficulty digesting lactose. Lactose is present in milk and foods which are made with milk. Lactose intolerance causes diarrhoea, stomach ache and bloating. See the separate leaflet called Lactose Intolerance.
Intolerance to food sugars
Intolerance to sugars in certain foods can occur. Fructose intolerance is the most common. Foods high in fructose include dried fruit, honey, sucrose, onions and artichokes. Sorbitol is another sugar to which you can be intolerant. It is found in chewing gum and 'sugar-free' sweets.
Check the leaflet of any medicines you are taking, as wind, gas or bloating can be side-effects. Metformin (a medicine for diabetes) and lactulose (a laxative) are well known to cause these symptoms. Antacids such as magnesium trisilicate help to combat indigestion but they can increase the amount of carbon dioxide produced in the stomach, and aggravate belching.
Diseases causing increased gas
Most people with gas-related symptoms have increased sensitivity to gas or have one of the causes of increased gas production mentioned above. However, occasionally these symptoms can be caused by diseases of the bowel. Sometimes, the illness can be short-lived. For example, acute gastroenteritis (also known as a 'tummy bug'), often caused by infection with a virus, can result in a short-term condition associated with increased gas.
Occasionally, gas-related symptoms can be features of long-term diseases. All of them can cause at least one gas-related symptom (ie tummy pain, excess wind or bloating).
Coeliac disease is caused by intolerance to a protein called gluten which is found in certain foods containing wheat, barley and rye. It principally affects the part of the gut called the small intestine. It can occur at any age. Symptoms are relieved by avoiding gluten-containing foods. See the separate leaflet called Coeliac Disease.
Inflammatory bowel diseases
The most common inflammatory bowel diseases are ulcerative colitis and Crohn's disease. Ulcerative colitis is a disease in which inflammation develops in the colon and the rectum (the large intestine). Crohn's disease is a condition that causes inflammation of the wall of the gut (gastrointestinal tract). Any part of the gut can be affected. The main symptoms of inflammatory bowel diseases are tummy pains and diarrhoea, but bloating and other gas-related symptoms can develop.
Diverticulitis occurs when small pouches in the wall of the large bowel ('diverticula') become infected. See the separate leaflet called Diverticula (Diverticulosis, Diverticular Disease, Diverticulitis).
Short bowel syndrome
Short bowel syndrome can be a complication of bowel surgery. If more than half the small bowel is removed during surgery this can cause difficulties in food absorption.
Small intestinal bacterial overgrowth
Small intestinal bacterial overgrowth is a poorly understood condition which is caused by an overgrowth of germs in the small intestine. It can be an aftermath of bowel surgery, and also occurs more frequently in people with diabetes, inflammatory diseases of the bowel and diverticulosis.
It may be associated with irritable bowel syndrome and can cause the same sort of symptoms, particularly bloating. Indeed, it is thought that some cases of irritable bowel syndrome may be caused by small intestinal bacterial overgrowth. Small intestinal bacterial overgrowth is sometimes treated with antibiotics such as metronidazole.
Scleroderma is a condition which causes thickening of the skin and sometimes the internal organs. When the gut is affected it can cause problems in stomach emptying and irregularity of bowel movement. This can lead to bloating, constipation and diarrhoea. See the separate leaflet called Scleroderma (Systemic Sclerosis).
Ovarian cancer is mentioned here because, although cancer of the ovary is not a disease of the bowel, it can cause symptoms which can be confused with bowel disease. These can include feeling full quickly or loss of appetite, tummy pains and bloating. See the separate leaflet called Ovarian Cancer.
This is caused by infection with a germ called giardia. One of the symptoms is belching up foul-smelling gas.
Do I need any tests for trapped wind or bloating?
Most people with these symptoms do not need any tests. However, you may need tests if you have more worrying symptoms. These can include:
- Persistent diarrhoea.
- Blood in the stools (faeces).
- Weight loss.
- Lack of appetite.
- High temperature (fever).
- Being sick (vomiting).
- Features of anaemia.
- Difficulty in swallowing (dysphagia).
The tests may include:
- A stool sample to check for blood, high levels of fat (which could suggest problems with food absorption) and infection.
- A lactose tolerance test.
- X-rays of your gut.
- Examination of your stomach or lower bowel, using a camera (endoscopy).
- A blood test for coeliac disease.
How to relieve trapped wind and bloating
People often ask how to stop bloating and how to get rid of a bloated stomach. There are several options available that will help with excessive flatulence and constant bloating.
Changes to your diet
It is known that there are some foods that make you bloated. Cutting down on these triggers will promote bloating relief. Keep a record of the foods and drinks you have and drink to see if there are any foods or beverages which could be associated with your symptoms. These can include milk and milk products, certain fruits and vegetables, whole grains, artificial sweeteners and fizzy drinks. Pulses, bran and fruit contain fermentable carbohydrates, sugars which are easily broken down by the digestive system. Not only do fermentable carbohydrates cause excess gas, but they also work with germs to cause tooth decay. Reducing your intake of the fermentable carbohydrates found in sugary foods can result in several health benefits.
If you are lactose-intolerant you will need to avoid lactose-containing foods. Talk to your doctor to find out how best to do this without developing complications such as calcium and mineral deficiency.
If you are fructose-intolerant you should avoid fructose-containing foods. Fructose is used as a sweetener in many processed foods; look for 'high in fructose corn syrup' on the label.
Live micro-organisms (probiotics) may be helpful, although the evidence is not conclusive. Probiotics are 'gut-friendly' germs (bacteria) such as lactobacilli and bifidobacteria. The specific strain of bacteria may be important but, on current evidence, it is difficult to advise which strain(s) to use.
Diets which combat constipation may be helpful. For example, soluble fibre such as linseed (up to one tablespoon daily) and oats are recommended.
Exercise has been shown to improve gas-related symptoms. This is partly due to the upright position, as lying flat tends to stop gas from moving round the body.
One word of warning: excessive flatulence and belching are common in female runners. The cause for this is unknown.
The treatment for trapped wind, gas and bloating is essentially changes to your diet and exercise, and treatment for any underlying cause. There is otherwise no good evidence for any particular medicine but the following may be tried:
- Simeticone for bloating. It is usually sold in combination with an antacid. Simeticone is also used for colic in babies and infants. Simeticone has not been found to be helpful in bloating related to irritable bowel syndrome.
- Medicines which encourage the movement of the gut (prokinetic medicines) can assist with bloating relief. They can be quite helpful as bloated stomach remedies if you have excessive belching and bloating. Most of these are prescription-only preparations but peppermint can be bought in various forms.
- Medicines which relieve spasm may also be helpful for bloating and distension. Medicines in this group, available without prescription, include mebeverine and alverine.
Carbon fibre underwear appears to be effective but is expensive. Charcoal pads and cushions are cheaper but may not be as effective.
These may be useful for people who have a low tolerance to a normal amount of gas in the stomach. Therapies which may help include mindfulness and cognitive behavioural therapy (CBT). Psychological therapies may also be helpful for people who have excessive belching, particularly where aerophagy is the cause. Aerophagy can also sometimes be helped by a speech therapist.
Further reading and references
Bendezu RA, Barba E, Burri E, et al; Intestinal gas content and distribution in health and in patients with functional gut symptoms. Neurogastroenterol Motil. 2015 Sep27(9):1249-57. doi: 10.1111/nmo.12618. Epub 2015 Jun 21.
Lacy BE, Gabbard SL, Crowell MD; Pathophysiology, evaluation, and treatment of bloating: hope, hype, or hot air? Gastroenterol Hepatol (N Y). 2011 Nov7(11):729-39.
Bendezu RA, Mego M, Monclus E, et al; Colonic content: effect of diet, meals, and defecation. Neurogastroenterol Motil. 2017 Feb29(2). doi: 10.1111/nmo.12930. Epub 2016 Aug 21.
Shah ED, Almario CV, Spiegel BMR, et al; Lower and Upper Gastrointestinal Symptoms Differ Between Individuals With Irritable Bowel Syndrome With Constipation or Chronic Idiopathic Constipation. J Neurogastroenterol Motil. 2018 Apr 3024(2):299-306. doi: 10.5056/jnm17112.
Youn YH, Park JS, Jahng JH, et al; Relationships among the lactulose breath test, intestinal gas volume, and gastrointestinal symptoms in patients with irritable bowel syndrome. Dig Dis Sci. 2011 Jul56(7):2059-66. doi: 10.1007/s10620-011-1569-2. Epub 2011 Jan 15.