There are two causes of gas buildup in the digestive system. Firstly, when we eat, drink or swallow saliva, we also swallow tiny amounts of air. This swallowed air accumulates in the gut.

Secondly, when we digest food, bacteria create gas, mainly hydrogen, methane, and carbon dioxide. When food decomposes in the digestive system, it can also produce sulfur, which can produce an odor on expulsion.

As the gas builds up, the body may need to eliminate it through the mouth, by belching, or passing wind through the anal passage.

Flatulence often occurs without the person being aware of it. The average person expels gas through the anus 8-14Trusted Source times per day.

Causes

Flatulence can result from normal bodily processes, or it may stem from a condition affecting the digestive system.

Exogenous sources are those that come from outside. We swallow air when we eat, drink, or swallow saliva, especially when the body produces excess saliva due to nausea or acid reflux.

Endogenous sources are inside the gut. Gas may arise as a by-product of the partial digestion of certain foods.

Why do some foods cause more gas

Certain foods containTrusted Source sugars, starches, and fibers that the body cannot fully digest. When these items pass to the large intestine, bacteria begin to break them down, creating gas.

Foods that cause flatulence tend to be those high in certain polysaccharides, particularly oligosaccharides, such as inulin. Inulin belongs to a class of dietary fibers known as fructans.

Examples of foods that can worsen flatulence include:

• vegetables such as cabbage, onions, and Brussels sprouts
• cereals, such as wheat or oats
• pulses, including beans and lentils
• dairy produce
• yeast in baked products, such as bread

Here are some reasons why some foods cause more gas, but there are others.

• Complex carbohydrates: Complex carbohydrates in beans are difficult for humans to digest. When the complex carbohydrates reach the lower intestine, bacteria feed on them and produce gas.
• Lactose intolerance: When people consume food that contains lactose, such as milk, and lack the enzymes to break it down, the bacteria feed on the lactose. In people with lactose intolerance, this produces large amounts of gas.
• Celiac disease: Intolerance to the protein gluten means that people with celiac disease have excessive flatulence when they consume barley, wheat, and rye.
• Artificial sweeteners: Sorbitol and mannitol are common in candies, chewing gums, and sugar-free sweet foods. Some people develop diarrhea, gas, or both when they consume these substances.
• Fiber supplements: Adding these too rapidly to the diet can cause flatulence, especially if they contain psyllium.
• Carbonated drinks: Fizzy drinks and beer may cause a buildup of gas in the intestinal tract.

Anyone concerned about how their diet may be causing flatulence should ask a doctor or a qualified dietitian for advice.

Conditions that can worsen flatulence

Certain health conditions can cause or worsen flatulence.

• Underlying health conditions: Some chronic conditions can cause flatulence, for example, Crohn’s disease, ulcerative colitis, or diverticulitis. Some types of cancer can lead to a blockage in the intestines.
• Gallbladder problems: Gallstones and cholecystitis can cause additional gas.
• Constipation: Feces can make it harder to expel excess gas, resulting in further accumulation and discomfort.
• Gastroenteritis and other intestinal infections: A viral, bacterial, or parasitic infection of the digestive system, or food poisoning, can cause a buildup of gas. Examples include Escherichia coli (E. coli) infection, amebiasis, and giardiasis.
• Antibiotics: These can upset the normal intestinal flora, or bacterial flora, in the gut, leading to flatulence.
• Laxatives: Regular and excessive use of laxatives can increase the risk of developing flatulence.

Other causes include pregnancy, a hernia, pancreatitis, Hirschsprung disease, premenstrual syndrome, endometriosis, and others.

If there are signs of poisoning or a blockage, or if there is blood in the feces, urgent medical attention is needed.