What is the mechanism of flatulence?

From the Guidelines

Flatulence occurs when excess gas builds up in the digestive tract and is expelled through the rectum, primarily due to swallowed air and bacterial fermentation in the intestines, as supported by the most recent study 1. The mechanism of flatulence involves the breakdown of undigested carbohydrates by bacteria in the large intestine, producing gases like hydrogen, methane, and carbon dioxide as byproducts.

• Foods high in certain carbohydrates, such as beans, lentils, broccoli, cabbage, and whole grains, often cause increased gas production.
• Some people lack sufficient enzymes to digest specific foods properly, like lactose in dairy products, leading to more fermentation and gas.
• The composition of intestinal bacteria also influences gas production, with some individuals naturally producing more gas due to their unique gut microbiome.
• The characteristic odor of flatulence comes from small amounts of sulfur-containing compounds produced during bacterial breakdown of proteins. Key factors that contribute to flatulence include:
• Swallowed air
• Bacterial fermentation in the intestines
• Undigested carbohydrates
• Unique gut microbiome
• Food intolerances, such as lactose intolerance Typically, passing gas 10-20 times daily is considered normal, though this varies widely among individuals, as noted in the study 1. It is essential to note that while some studies suggest that probiotics may have a positive effect on bloating and flatulence, the most recent and highest-quality study 1 does not recommend their use for treating bloating or distention due to potential negative impacts on the gut microbiome and lack of sufficient evidence. Instead, central neuromodulators, such as antidepressants, may be effective in reducing visceral sensations and improving symptoms of bloating and distention, as suggested by the study 1. Additionally, gut-related medications that treat constipation, such as secretagogues and 5-hydroxytryptamine 4 receptor agonists, may also help alleviate bloating symptoms, as reported in the study 1. Brain–gut behavioral therapies, including hypnotherapy and cognitive-behavioral therapy, may also be beneficial in treating bloating and distention, as supported by the study 1.

From the FDA Drug Label

Use relieves bloating, pressure and fullness commonly referred to as gas Purpose Antiflatulent

The mechanism of flatulence is not directly explained in the provided drug labels.

• The labels mention that simethicone is used to relieve bloating and gas, and is an antiflatulent.
• However, they do not provide information on the underlying mechanism of flatulence itself 2 2. The FDA drug label does not answer the question.

From the Research

Mechanism of Flatulence

The mechanism of flatulence involves the production of gases in the digestive system, primarily in the colon.

• The main sources of intestinal gases are:
  • Swallowed air
  • Carbon dioxide from gastric acid neutralization
  • Gases produced by intestinal bacterial colonies, including hydrogen, methane, and carbon dioxide 3
• Bacterial fermentation of undigested carbohydrates is a key process in the production of these gases.
  • The colon is home to a large population of bacteria, which break down carbohydrates that are not digested in the small intestine 4
  • The products of this fermentation include short-chain fatty acids, such as acetate, propionate, and butyrate, as well as gases like hydrogen, methane, and carbon dioxide 4, 5
• The formation of bubbles in the colon is thought to occur when the partial pressure of bacterial gases exceeds 90 mmHg, allowing bubbles to form and fuse 3
• The movement of these bubbles through the colon can lead to the release of flatus, which is rich in bacterial gases 3
• Factors that can influence flatulence include:
  • Diet: Foods high in lactose, wheat products, and other carbohydrates can contribute to gas production 6
  • Gut motility: Altered movement of the gut contents can affect the formation and release of gas bubbles 3
  • Bacterial colonization: The type and amount of bacteria in the colon can impact gas production and flatulence 4, 5

Factors Affecting Flatulence

• Diet plays a significant role in flatulence, with certain foods contributing to gas production.
  • A low-flatulence diet, which is low in lactose and wheat products, can reduce the frequency of gas passage 6
  • A 'fibre free' diet can significantly reduce the total volume of flatus produced, as well as the volume of fermentation gases like hydrogen and carbon dioxide 5
• The type and amount of bacteria in the colon can also impact flatulence.
  • Probiotic organisms, such as Bifidobacteria, can metabolize oligosaccharides and other carbohydrates, but may not significantly affect faecal short-chain fatty acid excretion 4
• Other factors, such as gut motility and the rheological properties of the gut contents, can also influence the formation and release of gas bubbles 3