Heads up: This post is a continuation of my basics series. I recommend reading this post about IBS first!

AKA: Maria talks about science.

Disclaimer: Both of my parents are biologists. Somehow, though, I hated science in school (especially chemistry). Now I’m about to talk to you about chemistry. The world is weird, isn’t it?


So. Another acronym. I can tell you what it stands for, if you like.
FODMAP = Fermentable Oligo-, Di-, and Mono- saccharides And Polyls.
Ah, yes, it’s all clear now right?


So forget what the acronym actually stands for. All you need to know is this:


FODMAPs = Fermentable carbohydrates.



Mmm yeah, carbohydrates. Remember how I hated chemistry? So when I started taking my diet seriously, I had this massive list of things that were low and high in FODMAPs. Don’t eat apples, bananas are ok. Blackberries will make you feel terrible, but raspberries won’t. It was impossible to remember everything, and nothing made sense. And so I tried to start figuring out why I certain things made me feel terrible, and what FODMAPs actually are, and I stumbled across this – fermentable carbs. And I was like, ok yeah I’ve heard those words before … hang on. What exactly are carbs again?



Very simply, carbs are chains of sugar. There are simple and complex carbohydrates (this sounded vaguely familiar), which are short and long chains of sugars, respectively. Generally, the longer chains of sugar (complex carbs) are starches, and are not considered FODMAPs. So rice and potatoes: fine for me to eat.

It’s the short chains of sugars (simple carbs) that cause trouble. Take, for instance, one of the most basic: fructose. (It’s just one sugar molecule by itself.) Fructose is found in high concentrations in many fruits, such as apples, blackberries, and peaches, which all make me feel terrible. Or lactose (two sugar molecules), which is in milk products. Also don’t make me feel great. 



Ok, so but why are those particular carbs hard for me (and many others) to digest? First of all, FODMAPs aren’t easily absorbed into my intestine. And this is where the fermentable part comes in. Fermentation is the process of bacteria eating sugar (carbs), producing gas.

Think about beer for a second. Brewers add yeast to the hops & grain. Yeast, which is a bacteria, eats the grain, which has been broken down into sugar, and the result = carbonation! (aka gas.) A similar thing happens in digestion. Bacteria in the intestine eats the sugar (carbs), producing gas. This is normal to a point, but FODMAPs are rapidly fermentable, which means that the bacteria produce a lot of gas in a small amount of time. Remember, FODMAPs aren’t absorbed easily into the intestine, so there are a lot of sugars for the bacteria to eat. So more sugar = more gas = a lot of discomfort and pain.

The end

Yikes! That was a lot of information (and I cut it down a ton too)! Let’s do a quick recap.

FODMAPs are specific types of carbohydrates. Carbohydrates are chains of sugar. The sugars aren’t absorbed very well in the intestine, rapidly eaten by the bacteria, producing lots of gas. Thus, digestive discomfort. Which is why I don’t eat foods with FODMAPs, and feel so much better for it.

For the sake of actually writing something that anyone – and not just dietitians and scientists – can understand, I’ve cut out a lot of information here. For instance, not all complex carbs are starches, and not all of them are FODMAP-free. There also is a reason for the “Fermentable Oligo-, Di-, and Mono-Saccharides And Polyls,” which I plan to cover in detail in a later series of posts.

If you’re still curious, refer to the resources page for more posts. For a complete list of FODMAPs, I highly recommend the Monash University app. It isn’t free, but they update it as they test new foods, and I’ve found it to be worth the investment.

If you’re looking for next steps, read my guide to getting started on the low FODMAP diet next!

Low FODMAP Pumpkin Lasagna | Go Messy or Go Hungry

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