Is Flatulence (Farting) Good for You? Depends on the Smell?!

2. The Makings of a Fart


A fart, also called gas, “passing wind” or flatulence, is caused by the internal buildup of gases that are formed during the process of digestion and respiration. The causes of farts and how they develop within the digestive tract vary considerably depending on the person and circumstance.

As you’ve probably experienced firsthand many times, some farts can be pretty foul-smelling and noisy, while others easily slip below the radar. Wondering how much farting is too much? A mostly healthy person might pass gas 14–18 times per day, sometimes not even realizing it because the farts are mostly silent and odorless. (1) Rather than how often you fart, however, you might want to take a look at the smelliness of your farts and to examine other digestive symptoms present in order to determine if it’s really become a problem.

Is there likely anything to be worried about when it comes to your gas? Yes and no. Some flatulence is normal, especially when eating a whole foods, high-fiber diet — but excessive gas coupled with other symptoms can be a sign that something inside is going wrong, especially when it comes to digestion of certain foods. Too much farting can be a warning sign that normal intestinal gas dynamics have become compromised. This might result in subtle dysfunctions in intestinal motility, bacteria growth or changes in the microbiome composition taking place.

Is it really “Gas”?

The main type of gas that gets trapped inside the body and leads to flatulence is nitrogen, which researchers estimate accounts for about 20 percent to 90 percent of all the gas that causes farts. Followed by nitrogen, carbon dioxide also contributes to the gaseous volume of farts (about 10 percent to 30 percent) along with oxygen (up to 10 percent), methane (around 10 percent) and hydrogen (about 10 percent to 50 percent). (2)

Methane and hydrogen are actually both flammable gases — which explains why you might have seen some cartoon characters light their farts with a flame when you were a kid! The combination of gases described above usually causes a smell because some contain sulfur, the same smelly compound found in foods like eggs or cruciferous vegetables.

Why is there such a range in the percentages of gases within a fart and the level of smelliness, depending on the specific person? This has to do with how much air is swallowed by someone in a typical day, the types of foods within someone’s diet, and also the internal chemical reactions taking place within the microbiome or intestines during digestion.

The severity of smells associated with farts mostly has to do with the percentage of different gases present in the body at any given time. Surprisingly, most of the gas within a fart is odorless, and only a very small percent (around 1 percent) causes the signature foul smell of farts. The reason for stinkiness in general comes down to how much sulfurous gasses form within the intestines. (3)

Within a fart, several sulfur-related compounds develop that contribute to the intensity of the fart’s smell. These include:

  • Hydrogen sulphide: This is the component of a fart that usually smells like rotten eggs. Not only does it smell unpleasant, but it’s also flammable and can be toxic when consumed in large amounts. The human body makes some of its own hydrogen sulphide, but interestingly, it’s also produced within the environment in things like swamps, sewage systems and certain types of explosive volcanic rock.
  • Methanethiol: This is found naturally within the human body, mostly within the blood and brain. Ever open up your refrigerator and get a strong whiff of leftover veggies? Methanethiol has a strong smell similar to cruciferous veggies. including broccoli or cabbage. This same compound also contributes to other types of body odors including bad breath.
  • Dimethyl sulphide: Here’s another chemical compound that contributes to the smelliness of veggies. This is responsible for the smell produced when you cook things like Brussels sprouts. It’s present in foods along with methanethiol and created from the formation of certain bacteria.

—> NEXT: The Underlying Causes of Farting

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Dr. Josh Axe, DNM, DC, CNS, is a doctor of natural medicine, doctor of chiropractic and clinical nutritionist with a passion to help people get well using food as medicine and operates one of the world's largest natural health websites: He is the author of the groundbreaking health book Eat Dirt, which uncovers the hidden causes and cures of leaky gut syndrome. Dr. Axe is an expert in digestive health, functional medicine, natural remedies and dietary strategies for healing. He has been featured on many television shows, including the Dr. Oz Show, CBS and NBC, and has his own Eat Dirt program running on select PBS TV stations. Dr. Axe founded one of the largest functional medicine clinics in the world, in Nashville, TN, and has been a physician for many professional athletes. is one of the most visited websites worldwide for healthy recipes, herbal remedies, nutrition and fitness advice, essential oils, and natural supplements.