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Beans Beans, The Magical Fruit…

The more you eat em’ the more you toot.
The more you toot, the better you feel.
So eat those beans with every meal.

That was a little rhyme my grandfather used to always say to me when he was eating beans at family gatherings. I am sure many of you are familiar with it as well. We all know that eating beans can lead to levitating bed sheets, drive significant others into different rooms, and allow our asses to move around more air than a window fan. However do you know why this happens? Let’s take a look at this though the eyes of science!

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Why do we fart in the first place?

Farting is just the expelling of trapped gasses from our digestive tract.

These gasses can get trapped in there by a number of mechanisms: Swallowing air with the foods we eat, from air trapped in those foods, from reactions taking place in our digestive systems that generate a gas, and finally as a byproduct from the metabolic workings of the various bacteria which reside in our digestive systems. With regards to beans, the important one in this list is bacterial metabolic processes. To understand why let us first discuss sugars, glycosidic bonds and digestive enzymes.

Sugars and Glycosidic Bonds and Digestive Enzymes

Sugars in the foods we eat usually do not exist as single molecules (monosaccharide, meaning one sugar) they are typically polymers (polysaccharide, multiple sugars). The sugar molecules themselves can exist in two different forms depending on how certain parts of them are oriented, we call these two different possible molecular orientations either alpha or beta. The easiest example to show to explain this is Glucose:

Source 1 and Source 2
I have put a red star by the part of the glucose molecule we are interested in (it’s an -OH, or hydroxyl group), and as you can see the α-Glucose has the hydroxyl group pointing down, while the β-Glucose has the hydroxyl pointing up. The direction that this group points matters because it is the part of the glucose molecule that gets bonded together to form polysaccharide chains. For glucose there are two types of polysaccharides that can be formed, those from α-Glucose called starch, and those from β-Glucose called cellulose:

Source 1 and Source 2 edited by me.

Here we can see that the way the monosaccharides are linked together into their polysaccharide form (the actual polysaccharides are many more linked together then what I show here) is very different. The enzymes required to break these complex carbohydrates down into their simple monosaccharide form (which we can use for energy) are also very different. The human body has the enzyme required to break the α-bond found in starch (called amylase) however we lack the any of possible enzymes necessary to break down cellulose (these are called cellulases and there are a variety of them). Because we cannot break down cellulose we refer to these indigestible plant sugars as fiber.

What Does This Have To Do With Beans and Farting @justtryme90?

More than you might think! Beans have a few unique sugars in them that like cellulose are indigestible for us humans, we just lack the enzymes. One of these sugars is called Raffinose:

Source
We lack the enzyme to break the glycosidic bonds in Raffinose called α-galactosidase but a number of bacteria that live in our digestive tracts have it! When we typically consume foods most of the sugars are broken down early on in our digestive processes and quickly absorbed by the body in the lower intestine before they reach the dense collection of microorganisms residing in our large intestines. However when we consume beans, the Raffinose just passes on by our digestive enzymes until it reaches those bacteria in the lower intestine. For them this is a feast! Their α-galactosidase is all fired up and ready to break this sugar down. The bacteria are able to grow and metabolize the sugar rapidly. One of the byproducts of all of this metabolism is the production of a large amount of gas. This same gas is then sent lovingly by you out into the world as your bean farts.

Over The Counter α-galactosidase

You can purchase α-galactosidase in the pharmacy department over the counter. It’s sold under the brand name “Beano.” Taking this prior to consuming beans allows for this Raffinose sugar to be broken down into simple sugars which can be absorbed by the body in the small intestine. This is how when you take Beano, you don’t get gassy. Since the gas is just a byproduct of the bacteria you already have, excitedly eating the sugars from the beans that you can’t normally digest! No more sugars… no more bean farts.

Concluding Remarks

So there you have it, next time you eat beans know those farts are all because of Raffinose (and a few other sugars) that you just can’t digest. That, and you’re actually passing second hand bacterial farts.

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. I am a PhD holding biochemist with a love for science. My future science blog posts will cover a range of topics in the biology/chemistry fields.

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