Digestion Pros Explain Why Your Farts Smelly Really, Really Disgusting
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Bring up farts and suddenly the most mature adult seems to morph back into an awkward middle-schooler. However,
passing gas is not only completely normal—but an important indicator of your
digestive health, which has a significant impact on your overall well-being.
“The digestive system is the body’s main way to take in and absorb nutrients, which is essential to sustain life, but it’s so much more than that,” says
Shilpa Ravella, M.D., a gastroenterologist at Columbia University Medical Center in New York City. “As a barrier from the outside world, it’s also one of the body’s main defenses against disease and the home of the
trillions of bacteria that play an essential role in health.”
And, yes, one of the digestive system’s everyday processes is producing gas. “People pass gas an average of 14 to 22 times a day,” says Marta Ferraz Valles, R.D., a dietitian with the
Mercy Medical Center Institute for Digestive Health & Liver Disease.
While having some gas is totally healthy, particularly foul-smelling (or constant) farts can indicate some sort of issues in the GI tract. Here, digestion experts share eight common causes of unusually smelly farts and when to see your doctor about it.
1. You ate a bunch of sulfur-heavy foods.
According to Dr. Ravella, super-smelly gas is often the result of eating foods rich in sulfur, which the digestive system breaks down into stinky compounds called sulfides. Two high-sulfur foods Americans eat a lot of:
meat and
eggs. Ever had gas that smells like rotten eggs? Yeah, that’s from a nasty by-product called hydrogen sulfide.
Other foods that can lead to sulfide-related smelly farts include garlic, sulfite-containing wines, and dried fruits preserved with sulfur dioxide, says Ferraz Valles.
2. …or noshed on some FODMAPs.
FODMAPs, a family of short-chain carbohydrates found in all sorts of foods, can also cause digestive issues that stink up your gas. “FODMAPs are poorly absorbed in the small intestine, osmotically active (meaning they increase intestinal water content), and are quickly fermented by gut bacteria,” says Dr. Ravella. For sensitive people, this can lead to more—and worse-smelling—gas.

A Low FODMAP Diet Could Ease Your Bloated Belly
Unfortunately for sensitive stomachs, all sorts of foods contain FODMAPs, including certain fruits (like watermelon and mangoes) and vegetables (like broccoli and Brussels sprouts), high-fiber grains, onions, dairy, and the list goes on, says Dr. Ravella.
You’ll also find FODMAPs like sugar alcohols (think sorbitol) and fructose in lots of processed foods, Ferraz Valles adds.
3. You’ve been loading up on fiber.
Fiber, the indigestible parts of the plants we eat, is an incredibly important part of our diet. In addition to supporting a healthy digestive system (and
regular bowel movements), it also makes us feel satiated after eating, helps stabilize our blood sugar, lowers cholesterol, makes maintaining a healthy weight easier, and helps us live longer, per
the Mayo Clinic.

The Beginner's Guide to Low-FODMAP: Easy Meal Plans, Recipes, and Tips to Calm Your Gut
Thing is, many Americans don’t regularly eat enough fiber—and suddenly loading up on it can cause some digestive upset and increased flatulence, says Ferraz Valles. (Beans and legumes, for example, are a common culprit here.)
Often, it takes a few weeks for the digestive system to adjust to increased fiber intake, which is why Ferraz Valles recommends gradually increasing intake to the recommended amount (25 grams a day for women under 50 and 38 grams a day for men under 50) and drinking plenty of water alongside fibrous foods like oats, apples, lentils, and berries.
4. One of your medications (or supplements) may be to blame.
Sad but true: All sorts of prescriptions, OTCs, and dietary supplements—even those meant to ease stomach issues—can affect your farts, says Ferraz Valles.
NSAIDs (think Advil),
antacids, diarrhea medications, chemotherapy drugs, multivitamins, and fiber supplements can cause changes in flatulence frequency and odor, she says. It’s inconvenient, yes, but not necessarily anything to be concerned about.
5. Or, lactose intolerance could be the issue.
Lactose, a natural sugar found in dairy products, is famously difficult for many adults to digest. “One of the most common reasons people may suffer from excessive gas is lactose intolerance,” says Ferraz Valles. “This can cause excessive gas and other gastrointestinal distress.” According to the
National Institutes of Health (NIH), approximately 65% of people have difficulty digesting lactose.
Since different dairy products contain different amounts of lactose (milk contains more than hard cheese, for example), people may notice worse symptoms after eating different types of dairy, says the NIH. However,
abdominal pain,
bloating,
nausea, and lots of smelly farts 30 minutes to 2 hours
after eating dairy indicate lactose intolerance.
6. It could be due to a gluten sensitivity (or celiac disease).
Gluten, the always-controversial protein found in grains like wheat, barley, and rye, can also contribute to problematic flatulence. “People who have celiac disease or non-celiac gluten sensitivities may experience excessive gas when consuming gluten,” says Ferraz Valles. In both cases, consuming gluten can also contribute to a slew of digestive issues, as well as
headaches, fatigue, and mood issues, according to the
Celiac Disease Foundation.
However, while genetic celiac disease can be identified through blood testing, identifying a gluten
sensitivity or intolerance typically just involves observing changes in symptoms after
removing gluten from the diet (which should be done under the supervision of a dietitian or doctor).
7. You could have a gut microbiome imbalance, like SIBO.
“Bacterial imbalances can certainly cause excessive and foul-smelling gas,” says Dr. Ravella. People with low bacterial diversity in their gut (which can be caused by frequent, excessive
antibiotic use or a diet low in fiber and high in animal products) often face this issue, Dr. Ravella says.

What Is SIBO? The IBS-Like Condition, Explained
Another common culprit, though, is small intestinal bacterial overgrowth,
also known as SIBO, she says. SIBO occurs when excess bacteria builds up in the small intestine, which can affect nutrient absorption and cause all sorts of digestive symptoms (including an uptick in flatulence).
8. It may be a sign of irritable bowel syndrome.
Irritable bowel syndrome, a condition in which dysfunction in the large intestine causes digestive issues like bloating and abdominal pain, and bouts of diarrhea and constipation, is yet another common culprit behind particularly smelly farts, according to the
Mayo Clinic.
Though frequent gas alone is not enough to diagnose IBS, changes in gas odor and production are common factors, says Dr. Ravella. Often, managing IBS involves making healthy diet and lifestyle changes—and
addressing stress.
When to see your doctor about smelly farts
Though gas varies from person to person, regularly stinky farts—when in combination with certain other symptoms—do warrant a trip to the doctor, as they can indicate serious conditions, like
colon cancer. According to Dr. Ravella, the following are cause for concern:
- Bloody stool
- Unexplained weight loss
- Fevers
- Severe abdominal pain
- Floating stools
- Vomiting
However, even consistently smelly farts accompanied by more minor digestive upset (like bloating) can indicate issues like
food sensitivities and bacterial imbalances, Dr. Ravella says. In these cases, a registered dietitian can help you evaluate and modify your diet to ease your symptoms.
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Lauren Del Turco Lauren Del Turco is a writer, editor, and social media/content manager, who has contributed to Men's Health, Women's Health, The Vitamin Shoppe, and more.
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