Flatulence, also known as breaking wind, passing gas, or farting, is a natural bodily function that helps to release gas from your body. While it is normal for farts to have a smell, some farts can be particularly pungent and unpleasant, and they can even be the source of embarrassment, depending on where you are when it happens. Truly foul-smelling gas is most often the result of a normal chemical reaction in the intestines, but it can sometimes also be an indicator of an underlying health condition.

What Is a Fart?

Flatulence is the medical term for a fart, which is the expulsion of gas from the intestines through the anus. The word flatulence comes from the name for the gas generated in the stomach and bowels: flatus. It is a normal part of the digestive process for a buildup of this gas to eventually be passed, but the volume and frequency can vary from person to person. A fart is a similar phenomenon to belching or burping, but in those cases the excessive gas is expelled up the esophagus and out the mouth.

The various chemical reactions in the small intestine and large intestine produce between 500 and 2,000mls of gas each day. Flatus can be composed of a number of different gases, but the most common components are methane, nitrogen, and carbon dioxide. The different smells that can be perceived depend on the ratio of these gases, which is influenced in large part by the foods we eat. The intestinal gas that tends to be behind most smelly farts is hydrogen sulfide, and it is typically described as smelling like rotten eggs.

Common Causes of Stinky Farts

It’s worth noting that most flatulence is odorless; in fact, it has been estimated that only about 1% of passed gas has an odor that the average human would find unpleasant. A lot of the odorless gas is caused by simply swallowing air during chewing and swallowing food. Yet when the smell has a strong odor, there are a variety of possible causes:

  • Food intolerance: Food intolerance is a condition in which a person has difficulty digesting certain foods or ingredients in food. Common examples are gluten intolerance (primarily celiac disease) and lactose intolerance (inability to fully digest dairy products). In addition to typical gastrointestinal symptoms like diarrhea, bloating, and abdominal pain, food intolerance can also cause smelly gas to build up in the digestive tract.
  • Dietary fiber: Sulfur is one of the biggest sources of smelly farts, and many high-fiber foods contain more sulfur than other types of food. So even if a person was producing a similar amount of gas, a high-fiber diet may make that gas relatively more smelly. Some of the foods known for their effect on gas are cruciferous vegetables like Brussels sprouts, broccoli, cabbage, and kale as well as lentils, beans, and other legumes.
  • Medication: There are certain medications that can cause someone to produce smelly gas as they make their way through the digestive system. One of the more common culprits is antibiotics, a type of medication that is prescribed to treat bacterial infections. In the process of killing off harmful bacteria, though, antibiotics can sometimes also kill off some of the beneficial gut bacteria that reside in the large intestine. The loss of these bacteria can cause an imbalance in the gut microbiome that can lead to more gas that smells worse.
  • Infection: Even apart from the potential side effects of antibiotics, some bacterial infections can cause gas to smell particularly bad. In this case the smell is a byproduct of sulfur-containing compounds produced by the bacteria. This is especially noticeable when the infection leads to overgrowth as with the condition known as SIBO (small intestine bacterial overgrowth).
  • Constipation: Constipation is a type of bowel dysfunction that is usually defined as having fewer than three bowel movements in a week. When this happens, stool sits in the colon as water continues to be absorbed; this makes it harder to pass the stool, but it also can lead to a buildup of gas. Whether this gas is especially foul-smelling is mostly dependent on what the person has been eating and how long the stool stays in the body.
  • Gastrointestinal conditions: Many problems related to the digestive system have similar symptoms. This means that any strong gassy odor could potentially be a symptom of a deeper problem. Two of the more common possible causes are irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD), a group of conditions that includes Crohn’s disease and ulcerative colitis.
  • Colon cancer: In very rare cases, really stinky farts may be a sign of colorectal cancer. This is because colorectal cancer often starts from a polyp, a small overgrowth of tissue in the lining of the digestive tract that can continue to grow and eventually cause a blockage that leads to a gas buildup. An important caveat, however, is that other symptoms like intestinal bleeding and unexplained weight loss would have to be present in order to be considered a sign of cancer.

    How Do You Prevent Smelly Farts?

    If the cause of the odor is a particular medical condition, treating that condition will likely improve both the odor and the presence of excessive gas. For most people, though, preventing the odor will involve making some adjustments to your diet and lifestyle. Below are some tips for how to limit smelly farts:

    • eat smaller meals and chew food slowly with your mouth closed
    • avoid eating foods that tend to lead to a bad smell
    • drink more water and avoid carbonated beverages
    • add probiotic foods like yogurt into your diet that are known to improve gut health
    • increase daily activity levels to improve overall digestive health and bowel motility
    • recent research has provided some evidence that limiting artificial sweeteners like sorbitol may decrease gassiness and bad odors

      When to Speak With a Gastroenterologist

      While flatulence in a public setting can lead to shame or embarrassment, it really is a natural bodily function that is normal for everyone. There are a wide variety of reasons why a natural buildup of gas could become especially smelly, and most of those reasons are harmless or not a reason for concern. Improving the situation may be as simple as starting a food journal and making note of the kinds of foods that are more likely to contain sulfur and lead to an unpleasant odor.

      In some rare cases, however, a habit of foul-smelling farts—when paired with other gastrointestinal symptoms—can be an indicator of a bigger problem. If you have been experiencing this kind of smell at the same time as having severe abdominal pain, nausea, vomiting, bleeding, fever, or unexplained weight loss, it may be time to speak with a digestive health specialist like any of the board-certified physicians at Cary Gastro. Please contact us today to request an appointment.