Flatulence is a natural bodily function that everyone experiences, yet it remains one of the most awkward topics to discuss. But have you ever wondered why some farts are silent and deadly while others are loud but odorless? Does the sound of a fart relate to its smell? Can eating beans really cause excessive gas? Is smelling farts actually good for your health? Let's debunk these questions by understanding the science of flatulence.
According to the NHS, farting (flatulence) is the process of passing gas from the digestive system out of the back passage. It's completely normal and something everyone experiences regularly.
The term comes from "flatus." Flatus is the medical term for gas generated in the stomach or bowels. There's even a scientific field dedicated to studying this phenomenon called flatology.
The gas production process begins in your digestive system. The stomach and small intestine cannot fully digest certain carbohydrates, including sugars, starches, and fiber found in many foods. This undigested food travels through the small intestine and reaches the large intestine.
Once in the large intestine, bacteria break down these undigested carbohydrates, releasing hydrogen and carbon dioxide during the process. Other bacterial species in the large intestine consume hydrogen gas and produce methane gas or hydrogen sulfide. Hydrogen sulfide is the most common sulfur gas in flatus.
The Truth: It's Actually the Opposite
This is perhaps the most common misconception about flatulence. Dr. Wendi LeBrett, MD, a double board-certified gastroenterologist and internal medicine physician with degrees from Stanford University and UC San Diego School of Medicine, explains the real science behind this phenomenon via an Instagram reel.
Loud farts are high-volume and primarily contain gases naturally found in the air, including oxygen, nitrogen, carbon dioxide, and hydrogen. These gases are odorless. Loud farts are mainly caused by swallowed air and things moving quickly through the digestive system. When this high volume of gas passes through the rectum rapidly, it causes vibration of the anal sphincter, creating that distinctive sound.
Silent farts, on the other hand, result primarily from the breakdown of compounds in the gut through fermentation. These farts contain sulfur-containing gases in small volumes. “They are small in volume and they exit the rectum more slowly, so they don't cause any sound, but they are lethal in smell,” said Dr. Wendi.
Your nose only needs a tiny amount of these sulfur compounds to detect them, making them "silent but smelly."
Loud farts tend to be less smelly because they contain primarily atmospheric gases. Silent farts are typically more pungent because they contain concentrated sulfur compounds in smaller volumes.
The Truth: Bean Flatulence Is Greatly Exaggerated
Beans have an infamous reputation for causing gas, but is it true? According to a study published in Nutrition Journal, people's concerns about flatulence from eating beans may be significantly exaggerated.
The research revealed some surprising findings:
Less than 50% of participants reported increased flatulence from eating pinto or baked beans during the first week of trials.
Only 19% experienced increased flatulence with black-eyed peas.
The study concluded: there is significant individual variation in response to different bean types. Not everyone experiences gas from beans, and the extent varies greatly from person to person.
The Truth: It's Not Beneficial, But There's Interesting Science Behind the Myth
This myth has circulated widely on the internet, but according to Hong Kong University of Science and Technology, it's largely false. However, there's fascinating science that led to this misconception.
The myth stems from legitimate scientific research about hydrogen sulfide. It is one of the gases that gives farts their distinctive smell. Research has shown that hydrogen sulfide produced within cells can have beneficial effects. It can modulate reactions in mitochondria and provide cellular protection under certain conditions, such as high blood glucose caused by diabetes.
Scientists at the University of Exeter identified a molecule called AP39 that can direct hydrogen sulfide to the mitochondria of stressed cells in controlled amounts, releasing the gas in a very slow manner. This enables researchers to administer hydrogen sulfide from outside the body and mimic natural protective processes. 2
However, the scientists explicitly stated at the end of their press release that they never claimed sniffing hydrogen sulfide brings any health benefits.
Why smelling farts doesn't work: For treatment to be effective, hydrogen sulfide must be delivered to the right cells at precisely the right dose. Smelling farts cannot achieve this targeted delivery or dose control. Smelling farts is not effective or beneficial as a form of disease treatment or prevention.
Flatulence is a universal human experience that doesn't deserve the embarrassment and misconceptions surrounding it.
What is flatology?
Flatology is the scientific study area dedicated to researching flatulence and the gases produced in the digestive system.
Why do some farts smell worse than others?
Farts smell worse when they contain higher concentrations of sulfur-containing gases like hydrogen sulfide. Others are due to odorless atmospheric gases like oxygen, nitrogen, and carbon dioxide from swallowed air, making them less smelly.
Does the sound of a fart relate to its smell?
Loud farts are typically less smelly because they're high volume and contain odorless gases that pass quickly through the rectum, causing vibration of the anal sphincter. Silent farts are more pungent because they're low volume, sulfur-rich, and exit slowly without creating sound.
1. Winham DM, Hutchins AM. Perceptions of flatulence from bean consumption among adults in 3 feeding studies. Nutr J. 2011;10:128. Published 2011 Nov 21. doi:10.1186/1475-2891-10-128
2. University of Exeter. (2014, July 9). Rotten egg gas holds key to healthcare therapies. http://www.exeter.ac.uk/news/research/title_393168_en.html