Why Beans Cause Gas

Bowl of pinto beans, lentils, kidney beans, navy beans, and lima beans

Verywell / Zorica Lakonic

It's not exactly something you would keep track of, but most people pass gas between 13 and 21 times a day. It can happen even while you're asleep.

Gas is part of the natural digestive process. However, many people find gas embarrassing, particularly if they pass an excessive amount of gas.

It's true that some foods cause someone to produce more gas than others. In particular, foods with a high fiber content are frequent offenders. They can cause bloating, too.

It's also true that most people do not get enough fiber in their diet and should eat more fibrous foods. One food that has an especially notorious reputation when it comes to gas is beans, a member of the legume family.

Beans are well known for their ability to cause flatulence, but the reason may surprise you. This article explains why they have this effect, and what you can do about it.

Understanding Gas

Intestinal gas consists of hydrogen, nitrogen, and carbon dioxide. These gasses are odorless. Another element exists in the intestinal gas of about one-third of people: methane.

It's unclear why some people's bodies produce methane and others do not. One way to tell if there is methane in gas is to look at the stool after going to the bathroom. People who produce methane typically have stools that float in water.

Sulfur is the substance that gives gas its distinctive odor. It follows, then, that eating foods high in sulfur—such as garlic, onions, broccoli, cauliflower, and cabbage—can cause your gas to be stinkier.

Why Beans Cause Gas

Beans (legumes) cause gas because they contain a particular type of sugar, called an oligosaccharide, that the human body cannot fully digest. Other sugars are broken down and absorbed in the small intestine. But the human body does not produce an enzyme that breaks down oligosaccharides.

Oligosaccharides in beans make it all the way to the large intestine undigested. Bacteria in the large intestine finally feed on these sugars.

Doing so causes fermentation (a chemical breakdown) and the production of gas. We release that gas as flatulence.

Other foods that enter the large intestine without being absorbed in the small intestine can cause gas, too. And stress can affect digestion and nutrient absorption. The result? More gas.

When to Call Your Doctor

Gas may be a natural function, but you should talk to your doctor if your symptoms:

  • Bother you—or others
  • Get worse
  • Couple with stomach pain, constipation, diarrhea, or weight loss.

Preventing Gas From Beans

To prevent gas that is caused by eating beans or other foods, the oligosaccharides must be broken down before they reach the large intestine.

An enzyme called alpha-galactosidase can do this. But you will need help since the human body does not produce this enzyme.

You can take this enzyme as a supplement right before a meal. Derived from the fungus Aspergillus niger, it is available in pill form under the brand name Beano and others.

Alpha-galactosidase may not be appropriate for people with diabetes. The increased breakdown of oligosaccharides can raise blood sugar.

Alpha-galactosidase may also increase levels of a sugar called galactose in the blood. People with the genetic disease galactosemia should not use it. People with this disorder can't process galactose, so the sugar builds up in the body to toxic levels and can lead to a wide range of complications.


Beans cause gas because they contain a type of sugar, called oligosaccharide, that the body cannot break down. Gas can cause pain and discomfort, but there is a supplement you can take for relief.

A Word From Verywell

As long as it's not causing pain or excessive bloating, gas is a normal part of the digestive process. In fact, gas is an indication that things are working the way they should in the intestines.

Gas doesn't cause any real harm, but taking steps to minimize it may be a priority if it bothers you or others. Talk to your physician if you believe you experience too much gas or discomfort.

Frequently Asked Questions

  • How can I cook beans so they don't cause gas?

    Soaking beans before cooking has been found to reduce the amount of raffinose and stachyose—two oligosaccharides (sugars) that cause flatulence. You can do this in two ways: Soak beans overnight or boil them for two or three minutes and then allow them to soak for an hour.

  • Is gas caused by eating beans good for you?

    In a way, yes. Gas is a byproduct of the fermentation that takes place in the gut as beans are being digested. The fiber and sugars in beans serve as food (sometimes called prebiotics) for "good" bacteria in the digestive system.

  • Does eating more beans cause less gas?

    Yes, eventually. You may notice an increase in gas at first when you add more beans to your diet. But as you eat them regularly, your stomach will adjust and you'll produce less gas.

5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. National Institute of Diabetes and Digestive and Kidney Diseases. Symptoms and causes of gas in the digestive tract.

  2. American Psychological Association. Stress effects on the body: Gastrointestinal system.

  3. National Institute of Diabetes and Digestive and Kidney Diseases. Treatment for gas in the digestive tract.

  4. The Bean Institute. Two ways to soak beans to reduce gas.

  5. Cleveland Clinic. What you should know about beans and the (embarrassing) gas they cause.

By Amber J. Tresca
Amber J. Tresca is a freelance writer and speaker who covers digestive conditions, including IBD. She was diagnosed with ulcerative colitis at age 16.