Farting is a natural bodily function, and the average person passes gas around 14 to 23 times a day. While passing gas is normal, the odor can sometimes be alarming. If you’ve noticed your farts smell particularly foul, perhaps even like sewage, you’re not alone in wondering what’s going on. While occasional smelly gas is usually nothing to worry about and often related to diet, persistently pungent farts, especially those smelling like sewage, can indicate underlying issues.
This article will explore the common reasons why your farts might smell like sewage, helping you understand when it’s just a matter of diet and when it might be a sign to consult a healthcare professional.
1. High-Sulfur Foods in Your Diet
One of the most frequent culprits behind sewage-smelling farts is the consumption of high-sulfur foods. Sulfur is a naturally occurring compound that, when broken down in your digestive system, can produce a smell reminiscent of rotten eggs or sewage. Many healthy and nutritious foods are naturally high in sulfur.
Common high-sulfur foods include:
- Cruciferous Vegetables: Broccoli, cauliflower, cabbage, Brussels sprouts, kale, and bok choy are notorious for causing smelly gas due to their sulfur content.
- Alliums: Garlic, onions, shallots, and leeks are also rich in sulfur compounds that contribute to fart odor.
- High-Protein Foods: Red meat, poultry, eggs, and even beans can be sources of sulfur, although vegetables are often the bigger contributors to fart smell.
Image alt text: A colorful assortment of cruciferous vegetables including broccoli, cauliflower, and cabbage, known to be high in sulfur and potentially cause smelly farts.
When these foods are digested, bacteria in your gut break them down, releasing sulfur-containing gases like hydrogen sulfide. This gas is responsible for the sewage or rotten egg smell you might notice. If your diet is rich in these foods, especially in large quantities, it’s highly likely they are the primary reason for your sewage-smelling farts. Simply moderating your intake of these foods can often significantly reduce the odor.
2. Food Intolerances and Malabsorption
Food intolerances, such as lactose intolerance or gluten sensitivity, can also lead to unusually smelly farts. When your body can’t properly digest certain foods, it leads to malabsorption, where nutrients aren’t fully absorbed in the small intestine. This undigested food then reaches the colon, where bacteria ferment it, producing gas.
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Lactose Intolerance: People with lactose intolerance lack the enzyme lactase, which is needed to digest lactose, the sugar in milk and dairy products. Undigested lactose ferments in the colon, leading to gas, bloating, and sometimes sewage-smelling farts.
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Gluten Sensitivity and Celiac Disease: Gluten, a protein found in wheat, barley, and rye, can be problematic for some. Non-celiac gluten sensitivity and celiac disease (an autoimmune disorder triggered by gluten) can both cause digestive issues, including increased and foul-smelling gas. In celiac disease, the intestinal lining is damaged, further impairing nutrient absorption and exacerbating gas production and odor.
Image alt text: Various dairy products like milk, cheese, and yogurt, representing foods that can cause smelly farts in individuals with lactose intolerance due to malabsorption.
If you suspect a food intolerance, pay attention to how you feel after eating certain foods, especially dairy or gluten-containing products. Consulting a doctor for allergy or intolerance testing can help identify specific triggers and guide dietary changes to improve your digestion and reduce smelly farts.
3. Medications, Particularly Antibiotics
Certain medications, while intended to improve health, can inadvertently disrupt the balance of bacteria in your gut, leading to changes in fart odor. Antibiotics are a prime example.
Antibiotics work by killing bacteria, both harmful pathogens causing infection and beneficial bacteria that reside in your gut and aid digestion. This disruption of the gut microbiome can lead to:
- Imbalance of Gut Flora: With fewer “good” bacteria, the digestion process can be altered, leading to increased fermentation and gas production.
- Overgrowth of Odor-Producing Bacteria: Some bacteria that thrive after antibiotic use may be more prone to producing sulfurous gases, contributing to sewage-smelling farts.
Image alt text: A close-up of antibiotic pills, illustrating medications that can disrupt gut bacteria and potentially cause smelly farts as a side effect.
If you’ve recently started taking antibiotics and noticed a change in your fart odor, it’s likely related to the medication. This effect is usually temporary and resolves once you complete the antibiotic course and your gut bacteria rebalance. However, if the symptoms are severe or persistent, discuss it with your doctor.
4. Constipation and Fecal Buildup
Constipation, characterized by infrequent bowel movements and difficulty passing stool, can also be a cause of sewage-smelling farts. When stool remains in your colon for an extended period, it allows more time for bacteria to ferment undigested food and waste products.
- Increased Bacterial Fermentation: Prolonged stool transit time in the colon means more substrate for bacteria to work on, leading to greater gas production and stronger odors.
- Odor Absorption: As waste sits in the colon, the odors produced can be reabsorbed into the body and expelled through gas.
Image alt text: A visual depiction of constipation with hard, compacted stool in the colon, highlighting how stool buildup can contribute to smelly farts.
Addressing constipation through increased fiber intake, hydration, and exercise can help regulate bowel movements and reduce the buildup of fecal matter, potentially alleviating sewage-smelling farts. Over-the-counter laxatives can provide short-term relief, but consulting a doctor is advisable for chronic constipation.
5. Bacterial Overgrowth or Infection
An overgrowth of bacteria in the small intestine (SIBO – Small Intestinal Bacterial Overgrowth) or a digestive tract infection can significantly alter gut function and lead to very smelly farts.
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Small Intestinal Bacterial Overgrowth (SIBO): In SIBO, bacteria that normally reside primarily in the colon proliferate excessively in the small intestine. This misplaced bacteria can ferment carbohydrates prematurely, leading to gas, bloating, and altered bowel habits, including foul-smelling gas.
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Digestive Tract Infections: Infections caused by bacteria like Giardia or C. difficile can disrupt the normal gut flora and cause inflammation and changes in digestion. These infections often present with diarrhea and abdominal pain, and the resulting gas can be particularly pungent and sewage-like due to the infectious process and altered bacterial activity.
Image alt text: An anatomical illustration of the small intestines, the area affected by bacterial overgrowth and infections that can cause significant changes in fart smell.
If you experience persistent sewage-smelling farts accompanied by other symptoms like abdominal pain, diarrhea, or bloating, especially if these symptoms are new or worsening, it’s important to seek medical attention to rule out bacterial overgrowth or infection.
6. Colon Cancer and Bowel Obstruction
While less common, a more serious cause of sewage-smelling farts can be colon cancer. Tumors or polyps in the colon can cause a partial bowel obstruction, hindering the normal passage of stool and gas.
- Partial Bowel Obstruction: Obstructions can lead to a buildup of gas and fecal matter in the colon, promoting increased bacterial fermentation and the production of foul-smelling gases.
- Changes in Gut Microbiome: Tumors can also alter the local environment in the colon, potentially influencing the types of bacteria present and their metabolic activity, which can affect fart odor.
Image alt text: An illustration depicting colon cancer within the colon, representing a serious condition that can, in rare cases, contribute to changes in fart odor.
It’s crucial to emphasize that colon cancer is not a common cause of smelly farts, and most people with smelly farts do not have colon cancer. However, if you experience a persistent change in bowel habits, rectal bleeding, unexplained weight loss, or persistent abdominal discomfort alongside sewage-smelling farts, it’s important to consult your doctor for a thorough evaluation to rule out serious conditions.
7. Dumping Syndrome After Bariatric Surgery
Individuals who have undergone bariatric surgery, particularly procedures that alter the stomach and small intestine like gastric bypass, may experience dumping syndrome. Dumping syndrome occurs when food, especially sugary foods, moves too rapidly from the stomach into the small intestine.
- Rapid Food Passage and Malabsorption: The accelerated transit of food can overwhelm the digestive capacity of the small intestine, leading to malabsorption and increased fermentation in the colon.
- Altered Gut Motility: Bariatric surgery can change gut motility and bacterial balance, contributing to altered gas production and odor.
Image alt text: An illustration showing different types of bariatric surgery, surgical procedures that can sometimes lead to dumping syndrome and altered fart odor.
Sewage-smelling farts can be a symptom of dumping syndrome, along with other symptoms like nausea, diarrhea, abdominal cramps, and lightheadedness after eating. If you’ve had bariatric surgery and experience these symptoms, discuss them with your surgeon or healthcare provider.
When to Seek Medical Advice
Occasional smelly farts are usually not a cause for concern. However, if you experience any of the following along with sewage-smelling farts, it’s advisable to consult a doctor:
- Persistent or worsening smelly farts: If the odor doesn’t improve with dietary changes or home remedies.
- Accompanying symptoms: Abdominal pain, bloating, diarrhea, constipation, nausea, vomiting, unexplained weight loss, or rectal bleeding.
- New onset of smelly farts: Especially if you are over 40 or have a family history of colon cancer or digestive disorders.
Your doctor can evaluate your symptoms, medical history, and conduct necessary tests to determine the underlying cause of your sewage-smelling farts and recommend appropriate treatment or management strategies. In most cases, the cause is benign and easily addressed, but it’s always best to seek professional advice when concerned about persistent or concerning symptoms.
