Most people pass gas about 15 times a day, but anywhere from a handful to 40 times falls within the normal range. Your intestines produce between 500 and 2,000 milliliters of gas daily, and that gas has to go somewhere. If you feel like you’re on the higher end, the cause is almost always traceable to what you’re eating, how you’re eating, or how your gut bacteria are processing what you give them.
Where Intestinal Gas Comes From
Five gases make up more than 99% of flatulence: nitrogen, oxygen, carbon dioxide, hydrogen, and methane. They come from two main sources. The first is air you swallow, which contributes nitrogen and oxygen. The second, and far more productive source, is fermentation by bacteria in your colon. Gut microbes are the sole producers of all the hydrogen and methane in your intestines. When those bacteria break down food your body couldn’t fully digest higher up in the digestive tract, they release gas as a byproduct. The more undigested material that reaches your colon, the more gas you produce.
Foods That Cause the Most Gas
The biggest gas producers are foods containing complex carbohydrates your small intestine can’t break down on its own. Beans are the classic example. They’re rich in a sugar called raffinose, a three-part molecule your body lacks the enzyme to split apart. Instead, it passes intact into the colon, where bacteria ferment it rapidly, producing carbon dioxide and other gases. That same fermentation process happens with other high-fiber and high-FODMAP foods: cruciferous vegetables like broccoli, cabbage, and Brussels sprouts, as well as onions, garlic, lentils, and whole grains.
Research from Monash University found that when both healthy people and those with irritable bowel syndrome ate high-FODMAP meals, everyone produced more gas and experienced more abdominal discomfort. The difference was that people with IBS were more sensitive to that gas, experiencing higher rates of pain from the same amount of fermentation. So if certain foods seem to hit you harder than they hit other people, that sensitivity is real and measurable.
Swallowed Air Adds Up
Not all gas comes from your gut bacteria. A surprising amount enters your body as swallowed air, a phenomenon called aerophagia. You swallow small amounts of air constantly, but certain habits increase the volume significantly:
- Eating too fast or talking while eating
- Chewing gum or sucking on hard candy
- Drinking through straws
- Carbonated beverages, which release carbon dioxide directly into your stomach
- Smoking
Some of this air gets burped out, but whatever passes beyond your stomach continues through the intestines and exits as flatulence. If you’ve recently picked up a gum habit or started drinking more sparkling water, that alone could explain a noticeable increase.
Lactose Intolerance and Enzyme Gaps
If dairy seems to be a trigger, your body may not be producing enough lactase, the enzyme that breaks down lactose (the sugar in milk). When lactase levels are low, undigested lactose travels to your colon, where bacteria break it down and create both fluid and gas. This is one of the most common digestive enzyme deficiencies worldwide, and it often develops gradually in adulthood. You might have handled milk fine as a teenager and notice increasing problems in your twenties or thirties.
The pattern is usually recognizable: gas, bloating, and sometimes diarrhea within a few hours of consuming milk, ice cream, soft cheese, or other dairy products. A simple way to test this is to cut dairy for two weeks and see if your symptoms improve, then reintroduce it and note what happens.
Bacterial Overgrowth in the Small Intestine
Normally, most of your gut bacteria live in the colon. But sometimes bacteria colonize the small intestine in unusually high numbers, a condition called small intestinal bacterial overgrowth, or SIBO. When that happens, bacteria start fermenting carbohydrates earlier in the digestive process, before your body has a chance to absorb them. More bacteria feasting on food means more gas and other byproducts.
SIBO tends to cause persistent, hard-to-explain gassiness along with bloating, abdominal discomfort, and sometimes diarrhea. It’s diagnosed through a breath test that measures hydrogen and methane levels. If your levels are above a certain threshold, it indicates an overabundance of gas-producing bacteria. SIBO is more common in people who’ve had abdominal surgery, take certain medications long-term, or have conditions that slow the movement of food through the gut.
Medications That Increase Gas
Several common medications can quietly increase flatulence. Fiber supplements like Metamucil and Citrucel are a frequent culprit, especially when you start them without ramping up slowly. Iron pills, multivitamins, antacids, opioid pain medications, and even some anti-diarrheal drugs can all cause gas and bloating as side effects. If your gas increased around the time you started a new medication or supplement, that connection is worth exploring.
How to Reduce Excessive Gas
Start with the simplest changes. Slow down when you eat, put your fork down between bites, and avoid talking with food in your mouth. Cut back on carbonated drinks and gum. These adjustments reduce swallowed air and can make a noticeable difference within days.
For food-related gas, a structured low-FODMAP elimination diet is one of the most effective tools. Developed by researchers at Monash University, it involves temporarily removing high-FODMAP foods (certain fruits, vegetables, grains, and dairy) for two to six weeks, then reintroducing them one category at a time. This process helps you identify your specific triggers rather than guessing. Many people find that only one or two food groups are responsible for most of their symptoms.
If you suspect lactose intolerance, try eliminating dairy or switching to lactose-free versions. For bean-heavy diets, soaking dried beans overnight and discarding the soaking water before cooking reduces their raffinose content. Increasing fiber gradually, rather than all at once, also gives your gut bacteria time to adjust without producing a surge of gas.
Signs Something More Serious Is Happening
Gas alone, even a lot of it, is rarely a sign of something dangerous. But gas paired with other symptoms can point to conditions like celiac disease, inflammatory bowel disease, or other digestive disorders. Pay attention if your gas comes with blood in the stool, unintentional weight loss, persistent diarrhea or constipation, vomiting, or heartburn. Severe gas that doesn’t respond to dietary changes also warrants investigation, since conditions like SIBO or food intolerances are treatable once identified.