Passing gas between 14 and 23 times a day is completely normal. If you’re well beyond that range, or your gas is unusually smelly or painful, something specific is almost always driving it, whether that’s what you eat, how you eat, or how your gut bacteria handle what arrives in your large intestine.
How Gas Forms in Your Gut
Five gases make up more than 99 percent of what your body expels: nitrogen, oxygen, carbon dioxide, hydrogen, and methane. Most of the gas in your stomach is simply swallowed air, which is mostly nitrogen. The more interesting action happens lower down. When food reaches your large intestine without being fully digested and absorbed, your gut bacteria go to work on it through fermentation. That fermentation produces hydrogen, methane, carbon dioxide, and fatty acids as byproducts. The more undigested material that arrives in the large intestine, the more gas your bacteria produce.
The smell comes from an entirely different set of compounds. When bacteria break down proteins from meat, eggs, and certain vegetables, they release hydrogen sulfide, the chemical responsible for that rotten-egg odor. So volume and smell have different causes: volume is mostly about fermentable carbohydrates, while smell is mostly about sulfur-containing proteins.
The Most Common Dietary Triggers
Certain carbohydrates are poorly absorbed in the small intestine and arrive in the large intestine largely intact, where bacteria ferment them rapidly. These are collectively called FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols), and they’re found in a wide range of everyday foods: onions, garlic, wheat, beans, apples, pears, milk, and mushrooms, among others. For some people the byproducts of that fermentation cause not just gas but bloating, cramping, and abdominal distension.
Fiber is another major contributor. Soluble fibers like those in oats, barley, and legumes are readily fermented by gut bacteria, which is actually part of why they’re good for you. They feed beneficial bacteria. But that feeding process produces gas, and a sudden increase in fiber intake, say from a new diet or supplement, can overwhelm your system before your gut adjusts. The recommended daily fiber intake for adults under 50 is 38 grams for men and 25 grams for women. If you’re nowhere near that and suddenly jump to those levels, expect a gassy transition period of a few weeks.
Sugar alcohols deserve special attention because they’re increasingly common in “sugar-free” and “keto” products. Sorbitol, xylitol, maltitol, and lactitol all share the same problem: your body lacks the enzymes to fully absorb them in the upper digestive tract. The unabsorbed portion reaches the large intestine, where bacteria ferment it and it draws water into the gut through osmosis. Maltitol, for instance, can cause noticeable flatulence at doses around 40 grams, roughly the amount in a few sugar-free candy bars. Erythritol is the one sugar alcohol that largely avoids this problem because it’s absorbed before reaching the colon.
Swallowed Air Adds Up Fast
Not all gas comes from fermentation. You swallow several milliliters of air with every normal swallow, and certain habits multiply that intake significantly. Eating too fast, talking while eating, chewing gum, sucking on hard candy, using straws, drinking carbonated beverages, and smoking all increase the amount of air entering your stomach. This swallowed air is mostly nitrogen and oxygen, which means it doesn’t typically smell, but it does increase the total volume of gas you pass. If your gas is frequent but not particularly odorous, swallowed air could be a major contributor.
Food Intolerances You Might Not Know About
Lactose intolerance is one of the most common and underrecognized causes of excessive gas. If your body doesn’t produce enough of the enzyme that breaks down lactose (the sugar in milk), that lactose passes undigested into your large intestine, where bacteria ferment it. Normally very little hydrogen is present in your breath, but in people with lactose intolerance, breath hydrogen levels rise sharply after consuming dairy. A clinical breath test considers a rise of 20 parts per million above baseline a positive result. Roughly 68 percent of the global population has some degree of reduced lactose digestion, so this is far from rare.
Fructose malabsorption works similarly. If your small intestine can’t absorb fructose efficiently, the excess ferments in the colon. High-fructose corn syrup, honey, apples, and pears are common triggers. Celiac disease, where gluten damages the lining of the small intestine, can also lead to malabsorption of multiple nutrients, producing persistent gas alongside other digestive symptoms.
When Gut Bacteria Are the Problem
Small intestinal bacterial overgrowth, or SIBO, occurs when bacteria that normally live in the large intestine colonize the small intestine instead. These misplaced bacteria begin fermenting food much earlier in the digestive process, producing large amounts of gas. In a study of over 1,400 patients tested for SIBO, about a third tested positive. Among those, roughly half produced primarily hydrogen, nearly 40 percent produced primarily methane, and about 11 percent produced both. The type of gas matters: hydrogen-dominant SIBO tends to cause diarrhea, while methane-dominant SIBO is more closely associated with constipation and bloating.
SIBO can develop after food poisoning, abdominal surgery, or as a consequence of conditions that slow gut motility. If your gas came on after an illness or seems disproportionate to what you eat, this is worth investigating with a healthcare provider through a breath test.
How to Reduce Your Gas
Start by identifying patterns. A food diary for two to three weeks, noting what you eat and when your symptoms peak, can reveal triggers faster than guessing. Common culprits include beans, cruciferous vegetables (broccoli, cabbage, Brussels sprouts), dairy, wheat, onions, and sugar-free products.
If you suspect FODMAPs, a structured low-FODMAP elimination diet can help isolate which specific carbohydrates bother you. This involves removing all high-FODMAP foods for two to six weeks, then reintroducing them one category at a time. Most people find they react to one or two categories, not all of them.
For fiber, the key is gradual increases. Adding a few grams per week gives your gut bacteria time to adjust, which typically reduces the gas response over time. Drinking more water alongside fiber also helps it move through your system more smoothly.
Addressing swallowed air is straightforward: eat more slowly, put your fork down between bites, limit gum and carbonated drinks, and avoid straws. These changes alone can make a noticeable difference within days for people whose gas is primarily air-based.
Signs That Something More Serious Is Going On
Gas by itself, even a lot of it, is rarely dangerous. But when it’s accompanied by other symptoms, it can signal a digestive disorder that needs attention. Unintentional weight loss, blood in your stool, persistent abdominal pain, fever, or a sudden change in bowel habits alongside increased gas could point to conditions like celiac disease, Crohn’s disease, or ulcerative colitis. A noticeable shift in your baseline, going from normal gas to significantly more frequent or painful gas without an obvious dietary explanation, is also worth discussing with a doctor.