Friday Weird Science: beans, beans, a magical fruit...

Apr 13 2012 Published by under Friday Weird Science

...the more you eat the more you toot!

Everyone knows that beans make you fart. It's something that's basically assumed to be a fact of life. Beans have high fiber, high fiber does things to your intestinal tract, and the net result is a chorus of flatulence and stink that makes you unfit company. I know many people who won't touch beans on a first date, for fear of the farts. So we think beans must cause farting...but is it TRUE?


(Oh sure, they look so innocent. Source)

Winham and Hutchins. "Perceptions of flatulence from bean consumption among adults in 3 feeding studies" Nutrition Journal, 2011.

Why study whether beans make you gassy? Well...why not? I mean, what else is science for!? But really, the authors of this study were interested in whether beans really make you cut the cheese because they are interested in health. A diet high in vegetables, including legumes (beans) is thought to be good for the prevention of chronic disease. And beans really are a wonderful fruit legume. They are high in protein (which is what they are most known for), but they are also high in vitamins and minerals and are a good source of fiber. Really, you can't go wrong with a bean.

But people avoid beans because of their wind-making prowess, and this means they could be missing out on an important addition to a healthy (and possibly gassy?) diet. So the authors wanted to determine if eating beans really did cause gas.

And beans can definitely cause gas. They not only contain a lot of fiber, they also contain resistant starches, which aren't easily broken down. This means they end up getting digested by bacterial fermentation in your intestines, and a side effect of fermentation? That's gas. But gas production could vary from person to person. There's also the possibility of adapting to the gas producing qualities (or maybe just losing your sense of smell and dignity). After all, many other cultures eat way more beans on a daily basis than most Americans do.

But we still worry. And so, to put the idea of beans and gas to bed, the authors conducted a series of three experiments.

In the first study, they had participants eat 1/2 cup of beans (either black eyed peas or pinto), or 1/2 cup of carrots as a control. They could eat them alone or put them in a recipe as they wished, for 8 weeks. Because of the blacked-eyed peas and pinto beans in this study, they referred to it as the BEP study, which reminds me forcibly of this:

In the second study, they did the same 8 week treatment, only this time with 1/2 cup of vegetarian baked beans (with the carrots as control). And the final study was either 1/2 can of pinto beans or a control soup per day for 12 weeks. All the patients were told not to eat any other beans during the course of the study.

And the results? When it comes to farting, bean type matters. Only 19% of patients complained of farting after black-eyed peas, while 47-50% complained the magical fruit gave them too many toots when they ate pinto beans or baked beans (one unfortunate carrot eating control did complain of really bad gas). But this was only in the first week. Farting reports dropped off in week two and by the end of the 8 weeks, they might as well have been eating carrots. But keep in mind, all the subjects who were eating beans KNEW what they were eating, and the psychological expectation of a mass o'gas could have affected the results.

It's important to note that they weren't just studying farts here. This study was part of a larger study on the effects of beans on heart disease risk, and they found significant improvements in things like lipoprotein profiles and cholesterol. So 1/2 cup of beans per day could definitely do some good, without causing too much bad air.

So it seems that low levels of beans are safe. But it's important to note that in all three experiments, people were consuming only 1/2 cup of beans per day. This isn't a lot, I mean, a good sized Taco Bell anything will pack at least double the punch. While the people in this study didn't fart excessively, I have to wonder if it's a result of low bean dose.

Finally, the authors do note that farting occurs most often when people increase fiber from a low fiber diet, and goes away as you get used to it. And this is basically what they saw. So if you need more beans in your diet, better to get them on the daily and suffer it out for a week or two (maybe in the middle of a desert or something if you think it will be really bad), and then maybe life will return to normal. And if you're really worried? Stick to black-eyed peas. They look a little safer.

Winham, D., & Hutchins, A. (2011). Perceptions of flatulence from bean consumption among adults in 3 feeding studies Nutrition Journal, 10 (1) DOI: 10.1186/1475-2891-10-128

11 responses so far

  • Jim Thomerson says:

    My wife bought a bag of freeze dried okra snacks. They were pretty good and I ate a couple of handful. A while later, I started farting loudly and almost continuously. My wife ate a couple and complained of diarrhea. We decided not to put the remainder out for the deer, but chucked them in the garbage instead. I eat lots of beans and there was no comparison to the effects of the okra. I've eaten okra in other forms without any reaction.

  • Ricki Lewis says:

    I have discovered that if you do a low-carb diet for a long time -- at least 6 months -- and then eat, say, an evil white bagel, you will fart your brains out. Loudly and odorifically. It ain't the beans. I can eat nothing but beans and never toot at all. Beans have been maligned. I love them. Especially big fat mushy limas cooked in chicken broth in a crockpot.

  • The Daleks says:

    As a vegetarian with a high fiber intake, my experience is that the fiber from legumes and other starches cause significant gas. Not so much with vegetables, except the cruciferous variety. I really like stir-fried broccoli and tofu, but will have it for dinner only if I know I'll be alone the next day.

    What helps is Beano. It's not perfect, but a 75% success rate isn't bad. And you have to follow the directions carefully, or it won't work at all.

  • Nkem says:

    Most traditional food preparation calls for beans and legumes to be soaked prior to cooking. This certainly isn't just to speed cooking. It makes them much more digestible (read more nutrient absorption) and less gas-producing. So perhaps the research question is to compare not only bean vs. non-bean but also consider manner of preparation

  • [...] One more for carb-lovers. (The brain uses about 20% of your carbohydrate intake and it likes a consistent supply). Beans are truly an amazing food that is sadly overlooked. They’re humble, but very smart. Not only are they loaded with fiber, vitamins, minerals and protein, they’re ridiculously cheap. An entire bag of beans usually costs only a few dollars and will provide many meals. Beans provide a steady, slow release of glucose to your brain – which means energy all day without the sugar crash. Don’t go eating a whole platter of frijoles, though – just 1/4 of a cup is fine (and the side effects are, um…well-known). [...]

  • [...] took 16 volunteers, and fed them an extra 200g of pinto beans (one of the best beans for producing some good gas) the night before and the morning of the experiment. They added some lactulose two hours before [...]

  • [...] Well, in my google research, I stumbled across this fabulous little blog that tells you all about beans, and why they do in fact make you gassy!http://scientopia.org/blogs/scicurious/2012/04/13/friday-weird-science-beans-beans-a-magical-fruit/  [...]

  • Sandra says:

    When cooking beans, add one garlic clove or a pinch of whole cumin; I add both; gas problem resolved!

  • owisabella says:

    [...] One more for carb-lovers. (The brain uses about 20% of your carbohydrate intake and it likes a consistent supply). Beans are truly an amazing food that is sadly overlooked. They’re humble, but very smart. Not only are they loaded with fiber, vitamins, minerals and protein, they’re ridiculously cheap. An entire bag of beans usually costs only a few dollars and will provide many meals. Beans provide a steady, slow release of glucose to your brain – which means energy all day without the sugar crash. Don’t go eating a whole platter of frijoles, though – just 1/4 of a cup is fine (and the side effects are, um…well-known). [...]

  • Neil Carr says:

    I've just had a meal of BEP and brown rice. I eat other beans fairly regularly - 3/4 times a week. However I started farting big time only 30-45 minutes after eating. Surely the beans hadn't yet reached the large intestine?

  • […] One more for carb-lovers. (The brain uses about 20% of your carbohydrate intake and it likes a consistent supply). Beans are truly an amazing food that is sadly overlooked. They’re humble, but very smart. Not only are they loaded with fiber, vitamins, minerals and protein, they’re ridiculously cheap. An entire bag of beans usually costs only a few dollars and will provide many meals. Beans provide a steady, slow release of glucose to your brain – which means energy all day without the sugar crash. Don’t go eating a whole platter of frijoles, though – just 1/4 of a cup is fine (and the side effects are, um…well-known). […]

Leave a Reply