Health Conditions A-Z Digestive Health Why Do My Farts Smell So Bad? Here's What Doctors Have to Say About Stinky Farts Here's what got you into this stinky situation. By Karen Pallarito Karen Pallarito Twitter Karen Pallarito tells stories grounded in science and backed by solid reporting. As Senior Conditions Editor for Health, she covers COVID-19 plus umpteen other health and wellness topics. Her freelance portfolio includes pieces for The Washington Post, U.S. News & World Report, Working Mother, Westchester Magazine, and the news syndicate HealthDay, among others. Karen started her career as a health policy reporter in the nation's capital, where she covered congressional hearings on Medicare and Medicaid. From the late 90s to the early aughts, she reported on health business for Reuters Health and contributed to its medical and consumer health newswires. Prior to that, she was Modern Healthcare's New York Bureau Chief. A fellow of the Association of Health Care Journalists' 2019 class on Comparative Effective Research, Karen is committed to helping people understand the benefits and harms of clinical interventions and exposing racial/ethnic disparities in healthcare. When not on deadline, you might find her whipping up something in the kitchen, working out, bingeing on cable news, or indulging in some form of mind candy (aka reality TV). health's editorial guidelines Updated on February 12, 2020 Share Tweet Pin Email Just in case you need to hear it: Farting is normal. People break wind an average of 14 times a day, emitting anywhere from half a liter to more than 2 liters of gas over a 24-hour period. And, believe it or not, 99% of gas is odor-free. But sometimes your farts are just downright funky, forcing you to ask yourself, "Why do my farts smell so bad?" Luckily, there's a pretty valid reasons for your not-so-pleasant smelling gas: "Silent-but-deadly ones, the really smelly guys, are due to fermentation by bacteria in your colon," says Patricia Raymond, MD, a Virginia Beach-based gastroenterologist and assistant professor of clinical internal medicine at Eastern Virginia Medical School. For more on digestive conditions, check out our Digestive Health Condition Center If you're having wicked gas, it's probably something you ate–and not necessarily a bad thing. Gas is a healthy, normal byproduct of digestion, after all. While the smell may be embarrassing in social situations, it might mean you've fed your gut nutritious, fiber-rich, plant-based foods. However, sometimes a bad odor can signal a more serious health problem requiring a thorough workup by a GI doc. Here are eight reasons why the gas you pass can sometimes be offensive. 20 Reasons Why Your Stomach Hurts 01 of 08 The bugs in your gut LightFieldStudios/Getty Images During digestion, gut bacteria produce sulfur-containing compounds like hydrogen sulfide that create a stench in your gas, Dr. Raymond notes. The foods you eat can influence the population of bacteria that live in your colon, which then affects your farts, explains Frederick Gandolfo, MD, a gastroenterologist at Precision Digestive Care in Huntington, New York. "Certain people have a certain type of flora inside of them that causes them to produce more gas or smellier gas," he says. 5 Sneaky Causes of Bloat and How to Avoid Them 02 of 08 Sulfur-rich foods Edelweiss Spykerman / EyeEm/Getty Images Foods high in sulfur can make your farts reek of rotten eggs. Cruciferous veggies like broccoli, Brussels sprouts, cauliflower, and cabbage are often to blame. Other sulfur-rich foods include garlic, onions, legumes, cheddar cheese, dried fruit, nuts, beer, and wine. Even animal proteins, like eggs, meat, and fish–all high in sulfur–may be problematic. In a small lab experiment involving seven healthy people, an Australian research team found that mixing poop with cysteine, a sulfur-containing component found in protein sources, resulted in a seven-fold increase in stinky hydrogen sulfide emissions. It may be why bodybuilders–who tend to consume a lot of protein powder–have notoriously foul farts, the lead researcher speculated. 13 Veggies You Only Think You Don't Like 03 of 08 Lactose intolerance Katri Lehtola/Folio Images/Getty Images Some people blame milk, ice cream, and cheese for stinking things up, and rightly so. An estimated 30 to 50 million Americans are deficient in the enzyme needed to digest lactose (aka, lactase), the natural sugar found in dairy products. In these folks, lactose passes through the small intestine without being absorbed, traveling downstream to the colon, where trillions of bacteria "have a little party," Dr. Raymond says. The effect is smelly gas, since milk and certain cheeses have a high sulfur content. People can also be intolerant to (and pass smelly gas from) other sugars, including sucrose (table sugar) and fructose (found in fresh fruit, corn syrup and some processed foods). 6 Things That Happen to Your Body When You Quit Sugar 04 of 08 Raffinose Getty Images Beans, beans. They're a rich source of protein, antioxidants, vitamins, and minerals. But, whoa, they get a bad rap for making you fart. Beans contain raffinose family oligosaccharides (RFOs), a group of sugars that are at least partially responsible for the bloating and gas that can occur after a beany meal. So do lentils, legumes, and cruciferous veggies. The human GI tract lacks an important enzyme needed to break down and digest these sugars. One study found that soaking dried beans in water helps remove RFOs without compromising the nutritional value of the beans. Taking an enzyme-based digestive aid (like Beano, for example) can also help ease symptoms. 9 Reasons You Should Eat More Beans 05 of 08 Sugar alcohols Dave Bradley/Getty Images Beware of sugar alcohols, like sorbitol and xylitol, which can be found in diet drinks, sugar-free candy, and some chewing gum. These sweeteners cannot be fully absorbed by the body, so they travel to the colon where they can contribute to awful-smelling gas. Keeping a food diary can help you determine if sugar alcohols are causing your stinky farts. Dr. Raymond recalls a female patient who had bad gas but only on weekdays. It turned out that a big bowl of sugar-free candies at her office was the culprit: The woman would grab some every morning, "and by late afternoon, in a business meeting, she would be passing lots of gas," Dr. Raymond remembers. 10 Artificial Sweeteners and Sugar Substitutes 06 of 08 Constipation Bagels, rice, and pasta aren't necessarily gas-producing carbs. But load up on these low-fiber picks, and you may have difficulty moving your bowels. That's when things get smelly. When you're constipated, poop "hangs around your colon for too long, and then bacteria can really go to town and cause lots of gas," Dr. Gandolfo says. To keep from getting backed up, drink plenty of water, exercise regularly, and include high-fiber foods in your diet, he says. 13 Surprising Reasons You're Constipated 07 of 08 Medicines Ivan Bajic/Getty Images Certain prescription drugs, vitamins, and supplements can do a number on your gut, including turning your farts foul. The reasons they cause flatulence differ by drug, and how much they'll make you gas (and how badly that gas stinks) varies from one person to the next, explains doctor of pharmacy Oralia Bazaldua, professor of family and community medicine at UT Health San Antonio. "Each person, along with their provider, will have to weigh the risks versus benefits of the offending agent," she says. 10 Side Effects of Antibiotics–and What to Do About Them People taking the weight loss medication orlistat commonly experience gas with oily discharge. Iron supplements are also known to cause gas and bloating. Supplements containing fiber can produce gas as a byproduct, and the diabetes drug metformin can also make you gassy. Diabetes drugs called alpha-glucosidase inhibitors, which slow carbohydrate absorption, can give you gas too. But don't use Beano with drugs in this class, Bazaldua says, because it can affect how well the medicine works. To get our top stories delivered to your inbox, sign up for the Healthy Living newsletter 08 of 08 Infection or disease GettyImages Smelly gas alone is usually nothing to worry about, Dr. Gandolfo says. But if you also have other signs and symptoms, get checked out. Talk to your doctor if you have fever, weight loss, blood in your stool, or persistent diarrhea alongside your stinky farts, or if you have a history of inflammatory bowel disease or colon cancer. Any change in your bowel habits or abdominal pain that doesn't go away after you pass gas or poop could signal trouble. It's important to rule out (or treat) other conditions that can cause smelly farts, says Dr. Gandolfo, including a bowel obstruction, inflammatory bowel disease (such as ulcerative colitis and Crohn's disease), colon cancer, celiac disease (an immune reaction to gluten), and C. difficile (a bacterial infection that causes diarrhea). 10 Risk Factors for Inflammatory Bowel Disease Was this page helpful? 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