Whether the body releases flatus, or intestinal gas, while a person is asleep is a common curiosity. This normal bodily function is a byproduct of the digestive process. Understanding the physiological changes that occur during rest helps to explain the mechanisms behind this unconscious gas release.
The Science of Unconscious Flatus Release
Individuals frequently pass gas without being aware of it during sleep. This unconscious release is a consequence of the body entering a state where sensory perception is significantly reduced. While awake, the sensation of gas accumulation in the rectum triggers a conscious response, allowing for regulation of its release.
During sleep, the brain’s ability to process and respond to these subtle internal signals is suppressed. This diminished awareness means the body is less likely to register the pressure change that precedes flatus release. The release of gas is often a purely involuntary event, bypassing conscious control. This is why most people who pass gas in their sleep find out if a partner or housemate informs them.
How Sleep Affects Muscle Control
The physiological mechanism permitting unconscious gas release is directly related to the relaxation of the body’s musculature during sleep. The body experiences a reduction in muscle tone, a state known as atonia, as it progresses through different sleep cycles. This includes the muscles responsible for maintaining continence.
The external anal sphincter, a muscle under voluntary control, relaxes more than it does while awake. The internal anal sphincter, which is involuntary, also has fluctuating pressure cycles throughout the night. This reduced vigilance of the external sphincter allows gas pressure that has built up in the colon to escape more easily. While the muscle tone is reduced, it remains sufficient to prevent the involuntary passage of stool in most cases, which requires a much greater relaxation.
Sources of Nocturnal Gas Production
Nocturnal gas originates from two primary digestive processes that do not cease during sleep. One source is aerophagia, which is the swallowing of air, often unconsciously, throughout the day. Activities like eating quickly, drinking carbonated beverages, chewing gum, or talking can cause a person to ingest air, which must eventually be expelled as a burp or flatus.
The second, and often more significant, source of intestinal gas is the bacterial fermentation of undigested food components, primarily carbohydrates, in the large intestine. Since the small intestine cannot fully break down certain complex carbohydrates, they travel to the colon where the resident gut bacteria feed on them. This fermentation process yields various gases, including hydrogen, carbon dioxide, and methane, which accumulate in the digestive tract. Because the digestive system continues to operate throughout the night, this gas production ensures a steady supply is available for unconscious release.