There are several natural causes of flatulence. Flatulence can also be caused by some health conditions related to the digestive system, or as a side effect of certain medicines.

Swallowing air

It's perfectly normal to swallow air while breathing and eating. However, it's easy to swallow a lot more air than usual without realising it. This can cause excessive flatulence.

Excess air can be swallowed by:

• chewing gum
• smoking
• sucking on pen tops or hard sweets
• having loose-fitting dentures
• not chewing food slowly and thoroughly – swallowing large pieces of food causes you to swallow more air

Hot and fizzy drinks also increase the amount of carbon dioxide in your stomach, although this is more likely to cause belching rather than flatulence.

Food and drink

Some carbohydrates in food can't be digested and absorbed by the intestines. These pass down into your colon to be broken down by bacteria, producing gas, which is released as flatulence.

Foods containing a high amount of unabsorbable carbohydrates include:

• beans
• broccoli
• cabbage
• cauliflower
• artichokes
• raisins
• pulses
• lentils
• onions
• prunes
• apples
• Brussels sprouts

Foods containing a lot of unrefined cereal fibre, such as bran, can also sometimes cause problems with wind and bloating.

Other foods and drinks that contain a sweetener called sorbitol (such as sugar-free gum or slimming products) or a type of sugar called fructose (such as fruit juice) can also cause flatulence. This means chewing sugar-free gum can cause flatulence from both the sweetener and swallowing air.

Certain foods, such as cabbage or onions, can lead to the production of gases containing sulphur, which can result in foul-smelling wind. However, the production of smelly wind can vary from person to person depending on what you eat, so it's up to you to work out which foods cause the most smell.

Health conditions

Certain health conditions can cause symptoms of flatulence, including:

• indigestion
• constipation 
• irritable bowel syndrome (IBS) – a common digestive condition, which can cause stomach cramps, bloating, diarrhoea and constipation
• coeliac disease – an intolerance to a protein called gluten, found in wheat, rye and barley
• lactose intolerance – where the body is unable to break down lactose (a natural sugar found in milk and dairy products) and can't absorb it into the blood
• gastroenteritis – a stomach and bowel infection
• malabsorption – where the intestines are unable to absorb nutrients properly
• giardiasis – an infection of the digestive system caused by tiny parasites

Medicine

Flatulence, often caused by indigestion, is a possible side effect of many types of medicine, including:

• non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen
• some laxatives
• antifungal medicines
• statins
• varenicline (Champix) – used to help people stop smoking