Stomach gas comes from two main sources: air you swallow and gas produced when bacteria in your large intestine ferment undigested food. Most people pass gas between 14 and 23 times a day, and that’s completely normal. When you’re consistently exceeding that range or feeling uncomfortably bloated, one or more specific triggers are usually responsible.
Swallowed Air
Every time you eat, drink, or swallow saliva, a small amount of air goes down with it. Certain habits dramatically increase the volume. Eating too fast, talking while eating, chewing gum, sucking on hard candy, drinking through a straw, and smoking all push extra air into your stomach. Carbonated drinks deliver gas directly, releasing carbon dioxide as the bubbles break apart in your digestive tract.
Some of this swallowed air comes back up as a burp. The rest travels into your intestines and eventually exits as flatulence. If you notice most of your gas is in the upper stomach (belching and a feeling of fullness), swallowed air is the likely culprit. Slowing down at meals and cutting out gum or straws can make a noticeable difference within a day or two.
Foods That Ferment in Your Gut
The biggest driver of intestinal gas is food that your small intestine can’t fully absorb. When these partially digested carbohydrates reach the large intestine, resident bacteria break them down through fermentation, producing hydrogen, methane, and carbon dioxide in the process.
The worst offenders belong to a group of short-chain carbohydrates researchers call FODMAPs, found in foods like onions, garlic, wheat, beans, lentils, apples, pears, and certain dairy products. In a controlled study, people eating a high-FODMAP diet produced roughly four times more hydrogen gas over the course of a day compared to a low-FODMAP diet. Even healthy volunteers with no digestive conditions reported increased flatulence on the high-FODMAP plan.
Fiber-rich foods like broccoli, cabbage, and whole grains also contribute. Fiber is essential for digestive health, but a sudden increase, like switching to a high-fiber diet overnight, can overwhelm your gut bacteria and cause a temporary spike in gas. Gradually increasing fiber over a few weeks gives your system time to adjust.
Lactose and Other Food Intolerances
If your body doesn’t produce enough of the enzyme that breaks down lactose (the sugar in milk), that lactose passes intact into your colon. Bacteria there ferment it rapidly, generating carbon dioxide, hydrogen, and methane, along with byproducts that pull water into the intestine. The result is gas, bloating, and often diarrhea after consuming milk, ice cream, soft cheese, or other dairy products.
Lactose intolerance affects a large percentage of adults worldwide, and the severity varies widely. Some people can handle a splash of milk in coffee without issue but react to a full glass. Others are sensitive to even trace amounts in processed foods. A simple way to test whether lactose is your trigger is to eliminate dairy for two weeks and see if your symptoms improve, then reintroduce it and track the response.
Sugar Alcohols and Artificial Sweeteners
Sugar-free gum, protein bars, diet candies, and many “no sugar added” products contain sugar alcohols like sorbitol, xylitol, mannitol, maltitol, and isomalt. These compounds are poorly absorbed in the small intestine, so they travel to the colon where bacteria ferment them, producing gas. They also have an osmotic effect: their presence in the gut draws water from surrounding tissues into the intestinal space, which can cause both gas and loose stools.
Sorbitol is one of the most common culprits. In the colon, bacteria convert it into smaller molecules with an even stronger water-drawing effect than other sugar alcohols. One exception is erythritol, which is absorbed earlier in the digestive tract and typically causes fewer gastrointestinal symptoms. If you chew sugar-free gum daily or regularly eat protein bars sweetened with sugar alcohols, those products alone could explain your symptoms.
Why Some People Feel More Gas Than Others
Two people can eat the same meal, produce the same volume of intestinal gas, and have completely different experiences. The reason is visceral hypersensitivity, a condition where the nerves in the gut respond more intensely to normal amounts of stretching and pressure. People with irritable bowel syndrome (IBS) are particularly prone to this. Their pain and discomfort thresholds in response to intestinal distension are measurably lower than in people without IBS.
This means the problem isn’t always that you’re producing too much gas. Sometimes your gut is simply more reactive to a normal amount. In the FODMAP study mentioned above, IBS patients produced more hydrogen gas than healthy volunteers on the same diet, but they also reported a wider range of symptoms, including bloating, abdominal pain, and even fatigue, while healthy participants noticed only increased flatulence. If your gas comes with significant pain or cramping, the sensitivity of your gut may be part of the equation.
What Actually Helps Reduce Gas
The most effective approach is identifying and reducing whatever is triggering the gas in the first place. A food diary, where you track what you eat and when symptoms appear, can reveal patterns within a week or two. Common strategies include:
- Eating more slowly and avoiding talking while chewing to limit swallowed air
- Cutting back on high-FODMAP foods temporarily to see if symptoms improve, then reintroducing them one at a time
- Checking labels for sugar alcohols in sugar-free and “diet” products
- Increasing fiber gradually rather than all at once
Over-the-counter options exist, but the evidence behind them is mixed. Products containing alpha-galactosidase (sold as Beano) work by breaking down specific hard-to-digest sugars found in beans and cruciferous vegetables before bacteria can ferment them. In a randomized trial, alpha-galactosidase reduced bloating and flatulence compared to a placebo. Simethicone, the active ingredient in Gas-X, works differently: it helps small gas bubbles merge into larger ones that are easier to pass. However, clinical evidence for simethicone’s effectiveness is weak, and many patients find it underwhelming.
Signs Something More Serious Is Going On
Gas by itself is rarely a sign of a dangerous condition. But certain accompanying symptoms warrant attention. Unexplained weight loss, blood in your stool, persistent diarrhea or constipation, or a sudden change in your gas patterns after years of normalcy can point to conditions that need evaluation. Persistent abdominal pain that doesn’t resolve after passing gas is also worth investigating, since gas pain typically eases once the gas moves through.