On Passing Gas

"A person produces about 30 to 91 cubic inches (500 to 1,500 milliliters) of flatus every day regardless of their diet, and over 99% of those gases are odorless".    But what happens when we hold that gas in?  What causes some gas to be really smelly?  Two articles posted on Live Science address these important questions.

First, when hold gas in, it will eventually come back out.  "The external anal sphincter is the only part of the digestive process we have conscious control over. So, if we decide the time is not right to pass gas, we constrict the sphincter and the fart is trapped. Without a backdoor to escape from, the gases recede back into the colon.  But primarily, the body is trying to push gas out. So farts that are ignored during the day are mostly released during bathroom breaks or as the body relaxes in sleep at night."

What causes that anally-expelled gas to smell?  There are many variables that affect this including that person's intestinal microbiota.  One major culprit is "Sulfur-rich foods include legumes (such as lentils, beans and peas) and brassicas (such as broccoli and cabbage). These fibrous veggies also contain insoluble carbs that bacteria in the colon may convert into stinky gas."


https://www.livescience.com/health/what-happens-when-you-hold-in-a-fart
What happens when you hold in a fart?
News
By Sierra Bouchér published 9/28/24

We all hold in farts from time to time, but where does the gas go?.

Imagine being on a first date when you feel the need to toot your own horn — that is, pass gas. The average person releases about 0.5 to 1.5 liters (0.1 to 0.4 gallons) of gas a day. Most of these farts are odorless, but it's rarely acceptable to take the chance and break wind. Whether in the workplace or with friends, we all clench our cheeks from time to time.

But what does holding in flatulence do to our bodies? Gas is a natural byproduct of digestion, and holding it in can cause discomfort, bloating and even nausea. But according to Dr. Ellen Stein, a gastroenterologist at RWJ Barnabas Health in New Jersey and a spokesperson for the American Gastroenterological Association, the body has other ways of handling this gas buildup.

"There's lots of different changes and cycles that happen with the bacteria that's in our gut that helps us to digest," Stein told Live Science. "The good news is that we have a process for it; the bad news is that gas has to pass eventually."

From the moment you take a bite of food, your body begins breaking it down mechanically and chemically. For instance, your teeth mechanically mash the food, and your saliva breaks it down chemically. As food travels down the digestive tract, it's broken down further in the stomach, small intestine and large intestine. Microbes in the gut help break down the food into its most basic building blocks. Then, these building blocks can be absorbed into the bloodstream and delivered throughout the body as energy.

But not everything in food can be used by the body, especially if the body can't fully break down certain substances. For example, people with lactose intolerance don't make enough of the enzyme lactase in their small intestine, so lactose, a sugar in dairy products, stays and ferments in the digestive system, causing symptoms such as bloating, diarrhea and excessive gas.

However, gas builds up even in typical digestion. According to the American Society for Microbiology, hydrogen sulfide (which can cause the rotten-egg smell in farts) is made by friendly bacteria in the gut that breaks down proteins. Farther down the digestive tract, carbohydrates are broken down in the large intestine, and their byproducts of hydrogen and methane are added to the gas building up in the body. Even oxygen and carbon dioxide can be present in the gut, taken in when a person swallows food, Stein said.

Farts are the natural way the body handles this unneeded gas. But before this gas can be released, it hits the anal sphincter. "That's the last stop: the control center … that tells you when to release a fart," Stein explained.

The external anal sphincter is the only part of the digestive process we have conscious control over. So, if we decide the time is not right to pass gas, we constrict the sphincter and the fart is trapped. Without a backdoor to escape from, the gases recede back into the colon.

But primarily, the body is trying to push gas out. So farts that are ignored during the day are mostly released during bathroom breaks or as the body relaxes in sleep at night.

While there is a time and place to let a toot loose, Stein said, always holding it in can be bad for the bowels over time. Small pockets called diverticula can form in your colon from the stress of consistent bloating, and they can become harmful if infected.

"Can you injure yourself by never passing gas?" she said. "Yes, the same way you can injure yourself by never pooping."

https://www.livescience.com/health/food-diet/which-foods-make-the-smelliest-farts
Which foods make the smelliest farts?
News
By Elana Spivack published October 2, 2023

Gastroenterologists describe the factors that go into passing gas and which foods make farts smell.

Nothing clears a room like a smelly fart. Even though this gas, known scientifically as flatus, is a part of our daily lives, we still know surprisingly little about what goes into it. So which foods make us the gassiest, and which ones make for the stinkiest farts?

A smelly fart usually starts with carbohydrates, especially insoluble ones that make it through the stomach and upper intestinal tract without being absorbed, Dr. Ali Rezaie, a gastroenterologist at Cedars Sinai in Los Angeles, told Live Science. Bacteria populating the colon thrive on these unabsorbed sugars, which are "like high-octane fuel for them," Rezaie said.

Although these carbs like fiber and starch weren't absorbed higher in the gut because our bodies lack the enzymes to break them down, bacteria, like those in the phylum Firmicutes in the colon, digest them easily. In feasting on these carbs, the bacteria produce gas, which can turn into farts.

However, not all of the gas that bacteria produce from food become smelly farts. A person produces about 30 to 91 cubic inches (500 to 1,500 milliliters) of flatus every day regardless of their diet, and over 99% of those gases are odorless, Rezaie said. Unscented gases — like methane, carbon dioxide and hydrogen — all contribute to farts, but gassiness doesn't necessarily correlate with stench.

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Offensive gases include hydrogen sulfide, known for its rotten-egg smell; indoles; and skatoles, "which, as the name implies, smells like poo," Dr. Eric Goldstein, a gastroenterologist at Mount Sinai Medical Center in New York City, told Live Science. But, when it comes to converting food into gas, it's not a one-to-one conversion rate in the gut.

"You can eat a ton of sulfur-containing compounds and have bacteria present that are making hydrogen sulfide," but "your flatulence will not smell like hydrogen sulfide," Goldstein said. Instead, the hydrogen-sulfide-producing bacteria may be counterbalanced by other bacteria feasting on that very compound. Sulfur-rich foods include legumes (such as lentils, beans and peas) and brassicas (such as broccoli and cabbage). These fibrous veggies also contain insoluble carbs that bacteria in the colon may convert into stinky gas.

Goldstein and Rezaie emphasized that many factors affect the volume and smell of flatulence. While we can assess common compounds in both foods and farts, some people have unique food sensitivities based on their gut microbiome. Insoluble sugars generally provide the basis for noxious gas, but there are no universal foods that become a polluting toot from every rear end.

"The gas production of bacteria in our gut is not just dependent on what you eat," Rezaie said. "It's all dependent on what other gas-producing bacteria in the gut that are feeding them other gases." Other factors — like gut motility, changes in bacterial composition, and how long it takes food to move through the gut — also influence how a fart might stew. What's more, farts also comprise swallowed air and gases diffused from the bloodstream, which are also odorless. These factors mean that a fart is more likely to be heard than smelled.

Disorders and intolerances also affect how bacteria produce gas. For example, in people who are lactose intolerant, the carbohydrate lactose makes it all the way to bacteria in the colon, which may leave someone farting up a storm that may or may not be smelly. Goldstein pointed to the FODMAP diet, a temporary elimination diet, as one way to reduce extreme cases of flatulence in those who are prone to it.

Still, Goldstein underscored that "there's really no clear one size fits all" when it comes to diet and farts, as myriad factors in each person's body interfere with all flatus. The measure of whether to seek help depends on how much flatulence disrupts someone's everyday life. On the other hand, farts — even stinky ones — are inevitable, and we can learn to forgive others and ourselves.