Passing Gas: Different Smells and What They Mean

The average person can pass gas, also known as farting, 6 - 20 times a day. That number might seem like a lot, but it’s true. With more than 500 different types of bacteria in your large intestine that aid in digestion and absorption of nutrients, you produce enough gas to fill one to three pints a day. Though passing gas can be embarrassing, flatulence is a natural part of the body’s digestive process.

It's good to be aware that excessive gas and changes in the smell of your flatulence can be signs of health concerns. The question is: What's normal when it comes to gas?

What Exactly is Passing Gas?

Gas is a natural byproduct of breaking down food you eat. After food and liquid enter the mouth, they're transported to the stomach via the esophagus. Enzymes in the stomach then break down food so it can be used by the body. Food and liquids continue to be broken down – separating proteins and carbohydrates – in the pancreas, liver and gallbladder. The small intestine becomes essential to digestion as it's where food and liquids consumed become nutrients absorbed by the body. Once passed to the large intestine, waste is broken down by bacteria and yeast. Here, the bacteria digest sugars found in the waste through fermentation, which creates gas.

More than 50% of the gas you release is nitrogen. Hydrogen, carbon dioxide, oxygen and methane make up the rest, along with sulfur, which is the source of gas’s odor.

What Causes Gas?

There are two reasons for gas: 

• Natural byproduct of the digestive process - Your digestive tract produces gas by breaking down undigested foods in the large intestine, also known as the colon. This process creates gases such as hydrogen, carbon dioxide and methane.
• Swallowing air - Gas is also caused by swallowing air, which happens when you chew gum, smoke, drink carbonated drinks or eat and drink large amounts too quickly. Instead of your body creating these gases (like nitrogen and oxygen) inside your colon, the flatulence caused by swallowed air comes from outside the body and travels through your digestive system. Aerophagia is the condition of swallowing very large amounts of air, which further increases gas.

Different Fart Smells and What They Mean

Sulfur compounds account for only 1% of your flatulence and causes gas to smell. Different types of sulfur compounds create different odors:

• Hydrogen sulfide, which is very common, produces a rotten egg smell.
• Methanethiol produces a smell similar to rotting vegetables or garlic.
• Dimethyl sulfide is often described as smelling like cabbage but might add a sweetness to the overall smell of gas.

Based on the bacterial composition of an individual’s digestive tract, the smell of gas could be one sulfur compound or a combination. 

Different bacteria produce different gases. The pungency of gas is also affected by how long it takes for your body to digest food. The longer it takes your body to digest food, the more time bacteria has to cause stronger odors when the gas is released. Eating foods high in fiber and drinking plenty of water will decrease the amount of time gas resides in your colon, causing less odor. Paying attention to your flatulence frequency and pungency is important as this could be your body’s sign of digestive issues and infections.

Why am I so Gassy Lately?

Certain carbohydrates are especially difficult for your body to digest. This group of short-chain carbs is known as FODMAP, which stands for “Fermentable, Oligo-, Di-, Monosaccharides and Polyols.” Foods high in FODMAPs include:

• Garlic
• Onions
• Asparagus
• Fruits high in fructose
• Milk
• Yogurt
• Fruit juice

These foods are poorly digested by the small intestine, leaving more waste to be processed by the large intestine, which is where the bacteria create gas. Individuals with normal digestive systems can eat these foods with only a mild increase in gas production. If foods high in FODMAPs cause abdominal bloating and pain, this could indicate an intolerance to certain foods that produce excess gas.

Which Foods Cause Gas to Smell Worse?

Since sulfur compounds produce the odor related to gas, eating foods high in sulfur compounds increase the pungency of your flatulence. Foods high in sulfur include:

• Meat
• Poultry
• Eggs
• Onions
• Garlic
• Broccoli
• Cabbage
• Brussel sprouts
• Cauliflower

Excessive Gas Could Be Sign of Digestive Disorders

Indigestion is difficulty digesting food that leads to bloating, abdominal pain and an increase in gas. Indigestion is caused by certain foods and drinks or due to emotional stress and anxiety. Indigestion is diagnosed by your primary care provider. It can also lead to disorders such as irritable bowel syndrome (IBS), ulcers or even stomach cancer.

Gastroenteritis (stomach flu) is caused by an infection that inflames the stomach and intestines. Symptoms of gastroenteritis include abdominal pain, bloating, vomiting and diarrhea.

Lactose intolerance occurs in individuals who lack the enzymes to digest sugars in cows’ milk and milk-based products such as creams or cheeses. If the small intestine can't digest the sugars in milk, digestion within the large intestine takes longer and can lead to excessive gas and a stronger smell.

Carbohydrate malabsorption causes abdominal pain and bloating due to an inability to digest wheat, rye and barley products. In its severe form, it's known as Celiac Disease.

Crohn’s Disease is thought to be caused by an overactive immune system that goes beyond attacking the bacteria it’s meant to repel and attacking the digestive system, instead. It leads to poor digestion that creates abdominal pain along with bloating, chronic diarrhea and rectal bleeding. Crohn’s Disease can also cause inflammatory bowel disease (IBD), which is a progressive disease of the intestines.

Irritable bowel syndrome (IBS) causes excessive gas as well as stomach pain and bloating. Though the cause of IBS is unknown, it's assumed to be associated with an overactive digestive system.

When Should Talk to Your Doctor About Gas?

Symptoms that indicate digestive problems:

• Excessive flatulence or strong odor (accompanied by other symptoms)
• Severe stomach/abdominal pain or bloating
• Diarrhea
• Constipation
• Blood in stool
  
• Nausea
• Vomiting

Talking about gas concerns with your doctor is never a taboo topic, changes in how often you're passing gas, or the smell, could be a sign of more concerning digestive issues. It's important to pay attention to your body and know what's normal for you. The better your doctor knows your body, the better he or she will be able to recognize changes that could be early warning signs, too. Call your care team or message them through My UnityPoint, our patient portal, if something with your digestive system feels off.