Published 20th September 2022

Why do beans give you gas?

Cannellini, pinto, black, kidney, and lima. The list of beans is long. 

Although they’re all subtly different, they have at least three things in common: They’re delicious, nutritious, and have a bad reputation for promoting farts.

In this article, we’ll explain why these nutrient-dense foods might increase the likelihood that you’ll release more wind.

We’ll also offer some tips on how to reduce beans’ ability to boost your gas. 

Then right at the end — plot twist! — we’ll turn this whole thing on its head and ask whether beans really do make people fart more than other veggies.

What’s in a bean?

Beans come fully packed with a range of nutrients, including protein, potassium, polyphenols, magnesium, folate, iron, and zinc. Most importantly for this article, though, they’re high in fiber.

Fiber is vital for gut health because it helps feed your gut microbiome. It also helps protect your overall health.

Beans are rich in soluble fiber. This type of fiber is water soluble and turns into a kind of gel in your gut. 

We can’t digest these compounds, but our gut bacteria love them.

As your gut bugs start to ferment the soluble fiber, they produce gasses. These build up and eventually work their way through your gut and exit via your butt.

Although beans are rich in soluble fiber, they’re not the only plants with high levels. Soluble fiber also occurs in a range of fruits, vegetables, and legumes.

So, what else do beans contain that makes them so windy?

Introducing raffinose

Aside from fiber, beans also contain raffinose. This is a type of carbohydrate called an oligosaccharide.

Humans can’t break down raffinose, but, once again, our gut bacteria do the work for us. And as they process this compound, they release lots of gas — specifically hydrogen, methane, and carbon dioxide.

Raffinose is not a bad actor, though. Instead, it acts as a prebiotic, a compound that promotes “good” bacteria and deters “bad” bacteria.

Beyond beans, raffinose occurs in lesser amounts in chickpeas, soybeans, lentils, cabbage, broccoli, and Brussels sprouts — another selection of foods famous for generating farts.

So, high levels of fiber and a healthy dose of raffinose appear to be the windy culprits.

Can you change the winds of fate?

We should mention that it’s normal to fart — if you have gas inside you, it needs to come out, whether up top or down below.

With that said, if you love beans but don’t want the added air, there are things you can do to reduce their malodorous music.

We asked ZOE’s U.S. medical director, Dr. Will Bulsiewicz, if he had any tips. Will is a board-certified gastroenterologist and a New York Times best-selling author.

We also asked ZOE’s senior nutrition scientist, Emily Leeming, Ph.D., for her insights.

First and foremost, Emily explained that your “gut microbiome produces gas as it metabolizes food — so it can also be a sign of a healthy gut.”

But for folk who are more sensitive, there are some things you can do:

1. Build up slowly

If you don’t usually eat a lot of fiber, it’s a good idea to build up slowly so that your gut — and its microbial residents — get used to the extra fiber.

Start small and work up.

2. Drink water

Emily explained that drinking water with a meal can help reduce flatulence.

Because some fiber absorbs water, it keeps things moving and lowers the risk of constipation — a risk factor for increased gas.

3. Prep and processing

Will told us that soaking dry beans overnight can reduce the amount of raffinose and related compounds, which will help reduce farts. 

When doing this, it’s important to discard the water the beans were soaked in and boil them in fresh water. 

Will also explained that repeatedly rinsing them can help — raffinose is water soluble, so this will wash a lot of it away.

Additionally, letting the beans sprout before cooking them or cooking them in more alkaline water can also reduce levels of oligosaccharides.

4. Movement

According to Emily, gentle movement, like a walk, after a bean-heavy meal can reduce the chances of excess farts.

5. Medication

Some over-the-counter remedies contain an enzyme called alpha-galactosidase. This enzyme breaks down raffinose and similar compounds.

Studies have shown that these products can reduce flatulence in healthy adults, children, and people with irritable bowel syndrome.

6. Onions?

According to one study that included more than 300 children in Nigeria, cooking beans with onion might also help reduce flatulence. 

Unfortunately, there doesn’t seem to be any other evidence to support this method, and onions also contain oligosaccharides, so it’s counterintuitive.

As Will explained, onions contain an oligosaccharide called fructans, which can cause flatulence in some people. 

With that said, onions and beans are a delicious combo, so it’s worth a try.

According to Will, cooking beans in a pressure cooker or with a strip of kombu seaweed can also help reduce bean-associated flatulence.

Are beans as bad as we think?

So, we’ve established that beans are particularly high in fiber and that raffinose boosts gas production. 

But we’ve also noted that beans aren’t the only food with these compounds. So, compared with other plants, are beans as bad as we’ve been led to believe?

According to a survey of dietitians, after they had recommended beans, clients commonly reported that excess gas was an issue. That’s a shame — beans are highly nutritious, relatively cheap, and tasty.

So, a group of researchers set out to see whether beans truly increase farts. 

Join our mailing list

Sign up for fresh insights into our scientific discoveries and the latest nutrition updates. No spam, just science.

The authors explain that, while people who don’t generally eat much fiber might be more likely to have increased gas after eating beans, “For some people, just the expectation of excessive flatulence from eating beans may influence their perceptions of having gas.”

Their study was three-pronged. The scientists compared self-reported flatulence after eating three types of beans: black-eyed peas, pinto beans, and baked beans. 

As a control, some participants ate canned carrots instead of beans. The studies ran for 8–12 weeks. 

Interestingly and importantly, at the end of the trials, participants who ate the beans had significantly lower levels of total cholesterol and “bad” cholesterol than the control group. 

But that’s not why we’re here. What about the farts?

In the pinto and baked bean trials, fewer than half of the participants noted an increase in flatulence. And in the black-eyed pea study, only 19% noticed a rise in farts.

Also, a small percentage of people eating the carrots (3–11%) reported an increase in farts.

And for the participants who did note an uptick in flatulence at the start of the study, their level of flatulence returned to baseline after a few weeks, the scientists found. So, although there was a short-term boost in gas, it settled down quite quickly.

We should note that these studies were small and measured perceived farts rather than the precise volume of wind. 

However, they show that — at least for some people — beans don’t make much difference to how windy they feel.

To bean or not to bean?

That is the question. 

In summary, don’t avoid beans just because of the theoretical increase in farts. Beans can form an important part of a varied, healthy diet. They should be revered, not feared.

At ZOE, we know everyone is different. Some people may experience an increase in gas after eating beans, but others might not. And those who have more gas at first might find that levels go back to normal if they continue eating beans over weeks and months.

Our bodies — and gut microbiomes — are unique. And they change. Work out what’s right for your body.

With that said, try some of our hints above if you're experiencing excess wind or bloating after eating beans. 

And if the bloating doesn’t improve, speak with your healthcare provider to make sure nothing else is going on.

Sources

Carbohydrate quality and human health: a series of systematic reviews and meta-analyses. The Lancet. (2019). https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(18)31809-9/fulltext 

Dietary fibre in foods: A review. Journal of Food Science and Technology. (2012). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3614039/ 

Efficacy and tolerability of α-galactosidase in treating gas-related symptoms in children: a randomized, double-blind, placebo controlled trial. BMC Gastroenterology. (2013). https://pubmed.ncbi.nlm.nih.gov/24063420/ 

Foods likely to cause gas. (n.d.). https://iffgd.org/gi-disorders/symptoms-causes/intestinal-gas/foods-that-may-cause-gas/ 

Increasing symptoms in irritable bowel symptoms with ingestion of galacto-oligosaccharides are mitigated by alpha-galactosidase treatment. The American Journal of Gatroenterology. (2017). https://pubmed.ncbi.nlm.nih.gov/28809383/ 

Legume promotion in counselling: an e-mail survey of dietitians. Canadian Journal of Dietetic Practice and Research. (2001). https://pubmed.ncbi.nlm.nih.gov/11742561/ 

Nutritional and health benefits of dried beans. The American Journal of Clinical Nutrition. (2014). https://academic.oup.com/ajcn/article/100/suppl_1/437S/4576589 

Perceptions of flatulence from bean consumption among adults in 3 feeding studies. Nutrition Journal. (2011). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3228670/ 

Raffinose family oligosaccharides: Friend or foe for human and plant health? Frontiers in Plant Science. (2022). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8891438/ 

Role of onion in reducing flatulence and other problems of indigestion among people eating beans in Imo State South East Nigeria. Journal of Biological and Genetic Research. (2000). https://www.iiardjournals.org/get/JBGR/VOL%201/ROLE_OF_ONION_IN_REDUCING_FLATULENCE.pdf 

Soaking and cooking modify the alpha-galacto-oligosaccharide and dietary fibre content in five Mediterranean legumes. International Journal of Food Sciences and Nutrition. (2019). https://www.tandfonline.com/doi/full/10.1080/09637486.2018.1544229 

The effect of oral alpha-galactosidase on intestinal gas production and gas-related symptoms. Digestive Diseases and Science. (2007). https://pubmed.ncbi.nlm.nih.gov/17151807/

Join our mailing list

Get occasional updates on our latest developments and scientific discoveries. No spam. We promise.