Gas comes from two sources: air you swallow and food that bacteria ferment in your colon. The average healthy adult passes gas about 10 times a day, with anything up to 20 times considered normal. If you’re exceeding that or dealing with uncomfortable bloating, the cause is almost always something you’re eating, drinking, or doing at the table.
Swallowed Air
Every time you eat, drink, or swallow saliva, a small amount of air goes down with it. Most of that air comes back up as a burp. But some travels further into the digestive tract and exits the other way. Certain habits dramatically increase how much air you take in:
- Eating too fast or talking while you eat
- Chewing gum or sucking on hard candy
- Drinking through a straw
- Carbonated beverages, which release carbon dioxide directly into your stomach
- Smoking
If your gas mostly shows up as frequent belching or a feeling of fullness in the upper abdomen, swallowed air is the likely culprit. Slowing down at meals, skipping the straw, and cutting back on sparkling water or soda can make a noticeable difference within days.
Foods That Ferment in Your Gut
The bigger source of flatulence is bacterial fermentation. Your colon is home to trillions of bacteria, and they feed on whatever your small intestine didn’t fully absorb. When they break down these leftover carbohydrates, they release hydrogen, methane, and other gases as byproducts. The more undigested material that reaches your colon, the more gas those bacteria produce.
Some carbohydrates are especially prone to fermentation. A group called FODMAPs (short-chain carbohydrates found in many everyday foods) consistently increases gas production. One study published in the journal Gut found that both healthy people and those with digestive symptoms produced more gas and experienced more abdominal discomfort after eating high-FODMAP meals. This isn’t a sign that something is wrong. It’s normal digestion doing exactly what it does with certain foods.
Beans and Legumes
Beans are notorious for a reason. They’re loaded with sugars called raffinose-family oligosaccharides, which your body simply cannot break down on its own. You lack the enzyme needed to split these sugars apart, so they pass intact into your colon where bacteria feast on them. Soybeans contain about 6 to 8 grams of these sugars per 100 grams. Lentils, peas, chickpeas, and faba beans all carry significant amounts too, with concentrations varying widely between varieties. The over-the-counter product Beano works by supplying the missing enzyme, helping break down these sugars before they reach your colon.
Cruciferous Vegetables and Alliums
Broccoli, cauliflower, cabbage, and Brussels sprouts contain both fiber and raffinose, making them double contributors. Onions and garlic are high in fructans, another type of fermentable carbohydrate. Cooking these vegetables softens fiber and can reduce gas somewhat, but won’t eliminate it entirely.
Whole Grains and High-Fiber Foods
Wheat, oats, and other whole grains contain fiber your body can’t digest, which is the whole point of fiber for gut health. But a sudden jump in fiber intake is one of the most common reasons people experience a wave of new gas and bloating. If you’re adding more fiber to your diet, increase gradually over two to four weeks to give your gut bacteria time to adjust.
Dairy and Lactose
Roughly 65 to 70 percent of the global population has some degree of lactose intolerance. If you’re among them, your small intestine doesn’t produce enough of the enzyme that breaks down lactose, the sugar in milk. That undigested lactose moves into the colon and gets fermented by bacteria, producing gas, bloating, and sometimes cramping or diarrhea. Symptoms typically hit 30 minutes to 2 hours after you eat or drink something containing lactose.
The severity varies a lot. Some people can handle a splash of milk in coffee but not a bowl of ice cream. Hard cheeses and yogurt tend to be easier to tolerate because fermentation during production breaks down much of the lactose. If dairy consistently gives you trouble, a lactase enzyme supplement taken with your first bite can help.
Sugar Alcohols in “Sugar-Free” Products
If you chew sugar-free gum, eat protein bars, or use low-calorie sweeteners, sugar alcohols may be a hidden source of your gas. These are carbohydrates that are only partially absorbed in the small intestine, leaving plenty for colon bacteria to ferment.
Not all sugar alcohols are equal. Sorbitol (also called d-glucitol) is one of the worst offenders and shows up in sugar-free candy, cough drops, and pharmaceutical syrups. Maltitol and isomalt can cause significant flatulence and diarrhea in large amounts. Xylitol is moderately tolerated. Erythritol, because of its smaller molecular size, tends to be absorbed before it reaches the colon and causes the fewest problems.
One complicating factor: people often blame the wrong food. If you eat beans and sugar-free candy at the same meal, you might assume the beans caused your gas when the sugar alcohols were the real issue, or vice versa. Paying attention to individual foods in isolation can help you identify your actual triggers.
When Gas Points to Something Deeper
For most people, gas is dietary. But persistent, excessive gas that doesn’t respond to food changes can signal a condition worth investigating.
Small intestinal bacterial overgrowth, or SIBO, occurs when bacteria that normally live in the colon colonize the small intestine instead. Food gets fermented earlier in the digestive process than it should, producing excess gas, bloating, and often diarrhea or constipation. Doctors diagnose it with a breath test: you drink a sugar solution, then breathe into a collection device at intervals. The test measures hydrogen and methane in your breath. A hydrogen rise of 20 parts per million or more within 90 minutes, or methane at 10 parts per million or above at any point, suggests bacterial overgrowth.
Other conditions that increase gas include celiac disease, where gluten damages the lining of the small intestine and impairs absorption, and irritable bowel syndrome, where the gut reacts more strongly to normal amounts of gas. Inflammatory bowel diseases like Crohn’s can also disrupt digestion enough to produce excess fermentation.
Practical Ways to Reduce Gas
Start with the simplest fixes. Eat more slowly, chew thoroughly, and finish one bite before taking the next. Switch from carbonated drinks to still water for a week and see if belching improves. If you chew gum daily, try stopping for a few days.
For flatulence specifically, an elimination approach works well. Keep a simple food diary for a week, noting what you eat and when gas is worst. Common triggers to test one at a time include beans, dairy, onions, garlic, broccoli, and sugar-free products. You don’t need to avoid these foods forever. Once you identify your triggers, you can manage portions or use enzyme supplements strategically.
Over-the-counter gas drops containing simethicone work differently than enzyme supplements. Simethicone doesn’t prevent gas production. Instead, it acts as a surfactant that merges small gas bubbles into larger ones, making them easier to pass as a belch or flatulence. It can relieve the uncomfortable “trapped gas” feeling but won’t reduce the total amount of gas your gut produces. For that, you need to address the source: either the food reaching your colon or the air going into your stomach.