Gas in the Digestive Tract: Why It Happens and How to Reduce It

Everyone has gas. Common symptoms are belching, bloating and passing gas, and some of each is normal, especially during or after meals. Gas becomes a problem when symptoms are frequent, bothersome, or get in the way of daily life.

The symptoms

• Belching (burping) releases gas from the stomach through the mouth. People typically belch up to 30 times a day; some belch more because they swallow a lot of air and release it before it reaches the stomach.
• Bloating is a feeling of fullness or swelling in the belly. When the abdomen actually gets larger, doctors call it distention — only about half of people with bloating have it. Some feel discomfort or pain as well.
• Passing gas through the anus is flatulence. Experts consider passing gas up to 25 times a day normal. Usually gas has no smell; odour comes from sulphur-containing gases released by bacteria in the large intestine.

Where gas comes from

1. Swallowed air. Everyone swallows some air when eating and drinking; air that is not belched can move into the intestines and pass out through the anus. You swallow more when you chew gum or suck hard sweets, drink fizzy drinks, eat or drink too fast, smoke, or wear loose dentures.
2. Bacteria in the large intestine. Some sugars, starches and fibre are not fully digested in the stomach and small intestine. Bacteria in the large intestine break them down and make gas in the process — so certain foods cause more gas, although a food that gives one person gas may not affect another.

Reducing gas

• drink plenty of water and non-fizzy drinks;
• eat more slowly, so you swallow less air;
• avoid milk products if you are lactose intolerant.

Medicines can reduce gas, or the pain and bloating it causes.

When to see a doctor

Talk with a doctor if gas symptoms bother you, if they change suddenly, or if you have other symptoms along with them, such as abdominal pain, constipation, diarrhoea or weight loss.

Sources

• MedlinePlus, U.S. National Library of Medicine, "Gas," drawing on the National Institute of Diabetes and Digestive and Kidney Diseases. https://medlineplus.gov/gas.html
• National Institute of Diabetes and Digestive and Kidney Diseases, "Symptoms & Causes of Gas in the Digestive Tract." https://www.niddk.nih.gov/health-information/digestive-diseases/gas-digestive-tract/symptoms-causes
• The two sources give different averages for how often people pass gas (13 to 21 times a day, and 8 to 14), so neither average is given here.
• Rewritten in hubnx's own words.