Pinto beans, navy beans, and baked beans are among the gassiest, with about half of people reporting increased flatulence when eating them. Black-eyed peas sit at the other end, causing noticeable gas in only about 19% of people. The difference comes down to specific sugars and fiber levels that vary significantly from one bean to another.
Which Beans Produce the Most Gas
A set of feeding trials published in the Nutrition Journal tracked how different beans affected real people’s digestion. In the first week of eating each bean type, 50% of participants reported increased flatulence from pinto beans and 47% from vegetarian baked beans (typically made with navy beans). Black-eyed peas caused increased gas in just 19% of people.
The pattern lines up with fiber content. Pinto beans and baked beans contain about 7 grams of fiber per half-cup serving, while black-eyed peas have 4 grams. But fiber is only part of the story. Beans from the Phaseolus family, which includes kidney beans, Great Northern beans, and California small white beans, have historically been used in flatulence research precisely because they’re known to be heavy gas producers.
Here’s a rough ranking from most to least gassy, based on both clinical observations and their sugar profiles:
- Most gas: Navy beans, pinto beans, kidney beans, Great Northern beans, baked beans
- Moderate gas: Chickpeas, lima beans, soybeans, cowpeas
- Least gas: Black-eyed peas, lentils, faba beans, mung beans
Why Beans Cause Gas in the First Place
Your small intestine lacks the enzyme needed to break down a family of sugars called raffinose and stachyose. These complex sugars pass through your stomach and small intestine completely intact, arriving in your colon undigested. There, trillions of bacteria ferment them as fuel, and the byproducts of that fermentation are gases: hydrogen, carbon dioxide, and in some people, methane. These three gases make up more than 99% of intestinal gas. The less than 1% of remaining compounds are the ones responsible for the smell.
The more of these sugars a bean contains, the more raw material your gut bacteria have to work with, and the more gas you produce. That’s why the type of bean matters so much.
The Sugar Content That Sets Beans Apart
Researchers have measured the raffinose and stachyose levels across dozens of legume varieties, and the differences are striking. Soybeans contain an average of about 8.3 mg/g of raffinose and 31.7 mg/g of stachyose, making them relatively high in gas-producing sugars. Lupins are even higher, with stachyose levels reaching 4.8 to 8.5% of dry weight. Lima beans clock in around 2.8% stachyose, and cowpeas range from 2.0 to 3.6%.
On the lower end, faba beans contain only about 0.7% stachyose and 0.2% raffinose. Mung beans and lentils fall in a similar low range, with stachyose levels between 1.0 and 2.7%. This helps explain why lentils and mung beans are generally easier on digestion than kidney or navy beans. Chickpeas are harder to pin down because their sugar content varies enormously depending on variety, ranging from 0.4% to over 59% stachyose in different cultivars. In practice, most common chickpea varieties fall in the moderate range.
How Soaking and Cooking Reduce Gas
The simplest way to cut down on gas is to soak dried beans before cooking and discard the soaking water. Research on common beans found that soaking and then draining reduced raffinose by 25%, stachyose by about 25%, and verbascose (another gas-producing sugar) by nearly 42%. Total sugars dropped by over 80% with this method. The key step is throwing out the soaking water rather than cooking in it, since the sugars leach out into that liquid.
A long soak of 8 to 12 hours works better than a quick soak. Cooking under pressure appears to break down even more of these sugars, though the exact reduction depends on time and temperature. If you’re using canned beans, much of this processing has already happened during the canning process, but rinsing them thoroughly before eating helps remove additional sugars sitting in the canning liquid.
Enzyme Supplements for Bean Gas
Over-the-counter enzyme supplements (sold under brand names like Beano) contain alpha-galactosidase, the enzyme your body doesn’t produce on its own. This enzyme breaks down raffinose and stachyose before they reach your colon, so there’s less for bacteria to ferment. In a randomized, double-blind trial, only 19% of people taking the enzyme reported flatulence compared to 48% on a placebo. The enzyme also reduced severe bloating by about two days per week.
You take these supplements with your first bite of beans, not after the gas has already started. They work best when the sugars are still in your stomach and small intestine, before reaching the colon.
Your Gut Adapts Over Time
One of the most useful findings from the feeding trials is that gas symptoms decreased the longer people kept eating beans. The initial spike in flatulence that half of participants experienced in week one dropped noticeably by weeks two and three of consistent daily consumption. Your gut bacteria gradually shift their population in response to a steady supply of these sugars, becoming more efficient at processing them with less gas as a byproduct.
If you’re adding beans to your diet, starting with lower-gas options like black-eyed peas or lentils and eating them regularly gives your digestive system a chance to adjust. Jumping straight to a large bowl of navy bean soup after months of not eating legumes is a reliable recipe for discomfort. Gradual increases in portion size, combined with proper soaking, make the transition much smoother.