Passing gas up to 25 times a day is normal for a healthy adult. If you feel like you’re gassy all the time, you may be producing more gas than average, noticing it more than usual, or both. The cause almost always traces back to one of three things: swallowed air, bacterial fermentation of food in your colon, or an underlying issue with how your body digests certain nutrients.
How Your Body Makes Gas
Your large intestine is home to trillions of bacteria that help break down food your small intestine couldn’t fully absorb. When these bacteria ferment leftover carbohydrates, they produce carbon dioxide, hydrogen, and sometimes methane. No human cell can produce hydrogen or methane on its own. Every bit of those gases in your gut comes from bacterial activity.
The composition of your gut bacteria matters. Some people harbor bacteria that convert hydrogen into methane, while others have bacteria that produce hydrogen sulfide, the compound responsible for foul-smelling gas. Your personal mix of gut microbes helps explain why certain foods make you gassy while the same foods barely affect someone else.
Foods That Cause the Most Gas
Certain carbohydrates are poorly absorbed in the small intestine, which means more of them reach the colon for bacteria to ferment. The biggest offenders include:
- Beans and lentils: High in raffinose, a complex sugar humans lack the enzyme to break down on their own.
- Cruciferous vegetables: Cabbage, cauliflower, broccoli, and Brussels sprouts also contain raffinose.
- Onions, garlic, and artichokes: Rich in fructans, another type of fermentable carbohydrate.
- Sugar alcohols: Sorbitol and mannitol, found in sugar-free gums and candies, pass through to the colon largely undigested.
- High-fiber foods: Whole grains, fruits, and vegetables are healthy, but a sudden increase in fiber gives your gut bacteria a feast.
If you recently changed your diet to include more of these foods, that alone could explain the uptick in gas. Your gut bacteria typically adjust over a few weeks, so the problem often improves with time rather than requiring you to cut these foods out permanently.
Swallowed Air Adds Up Fast
Not all gas comes from fermentation. A surprising amount enters your body as swallowed air, a process called aerophagia. You swallow small amounts of air with every bite of food and sip of water, but certain habits dramatically increase the volume:
- Eating too fast or talking while eating
- Chewing gum or sucking on hard candy
- Drinking through straws
- Carbonated beverages
- Smoking
Swallowed air primarily causes burping, but some of it travels past your stomach and eventually exits as flatulence. If your gas is mostly odorless, swallowed air is a likely contributor. Slowing down at meals, taking sips from a glass instead of a straw, and cutting back on gum can make a noticeable difference within days.
Lactose and Fructose Intolerance
About 68% of the world’s population has some degree of lactose malabsorption. If you’re among them, your small intestine doesn’t produce enough of the enzyme that breaks down lactose, the sugar in milk. Undigested lactose travels to your colon, where bacteria ferment it into hydrogen, carbon dioxide, and methane. The result is gas, bloating, and often cramping within a few hours of eating dairy.
Fructose works similarly. Some people absorb fructose poorly, and the excess reaches the colon and feeds bacteria. High-fructose corn syrup, honey, apples, pears, and fruit juices are common triggers. You might not connect the gas to these foods because the symptoms can take hours to appear, making the link easy to miss.
A simple way to test either one: eliminate dairy or high-fructose foods for two to three weeks and see if your symptoms improve. If they do, you’ve likely found your answer.
When Your Gut Bacteria Are in the Wrong Place
Sometimes the problem isn’t what you eat but where your bacteria live. In a condition called small intestinal bacterial overgrowth (SIBO), bacteria that normally thrive in the large intestine colonize the small intestine instead. Because the small intestine is where most nutrient absorption happens, these misplaced bacteria get first access to your food and start fermenting it before your body can absorb it. The result is persistent gas, bloating, and sometimes diarrhea.
SIBO is diagnosed through a breath test that measures hydrogen and methane after you drink a sugar solution. Hydrogen levels above 20 parts per million or methane above 10 parts per million in the first 90 minutes point toward overgrowth. If you’ve been gassy for months regardless of dietary changes, SIBO is worth investigating with your doctor.
Irritable Bowel Syndrome and Chronic Gas
IBS is one of the most common reasons people deal with persistent gas and bloating. It affects how your gut moves food along and how sensitive your intestines are to stretching. People with IBS often produce a normal amount of gas but experience more discomfort from it because their intestinal nerves are more reactive. A gut that’s technically producing an average volume of gas can still feel painfully bloated.
IBS typically comes with a pattern: recurring abdominal pain tied to bowel movements, along with changes in stool frequency or consistency. If your gas comes with alternating constipation and diarrhea, or if symptoms flare during stressful periods, IBS is a strong possibility. A low-FODMAP diet, which temporarily restricts the fermentable carbohydrates that feed gut bacteria, is one of the most effective approaches and reduces symptoms in roughly 70% of people with IBS.
Over-the-Counter Options That Help
If gas from beans and cruciferous vegetables is your main issue, an enzyme supplement containing alpha-galactosidase (sold as Beano) can help. This enzyme breaks down raffinose before it reaches your colon. In controlled studies, people who took it with a bean-heavy meal had significantly fewer gas episodes and lower total symptom scores compared to those who took a placebo. You take it with the first bite of the problem food, not after symptoms start.
For lactose intolerance, lactase enzyme tablets work the same way, supplying the enzyme your body doesn’t make enough of. Simethicone (Gas-X) takes a different approach: it doesn’t reduce gas production but breaks large gas bubbles into smaller ones, which can relieve the pressure and bloating sensation. It won’t cut down on flatulence, but it can make the discomfort more manageable.
Signs Something More Serious Is Going On
Gas by itself, even a lot of it, is rarely a sign of something dangerous. But pay attention if it comes alongside unintentional weight loss, blood in your stool, persistent diarrhea lasting more than a few weeks, or pain that wakes you up at night. These symptoms can point to inflammatory bowel disease, celiac disease, or other conditions that need proper evaluation. Fever alongside digestive symptoms is another reason to get checked sooner rather than later.
If you’ve tried dietary changes for a few weeks without improvement, keeping a food diary can help you and your doctor spot patterns you might otherwise miss. Track what you eat, when symptoms appear, and how severe they are. That record is often more useful than any single test in pinpointing what’s driving the problem.