Living with IBS can often feel like navigating a minefield: one wrong bite and your gut lets you know about it. The low-FODMAP diet has been shown to reduce symptoms in most people with IBS by lowering the number of foods that are most likely to trigger gut symptoms. But it can also feel restrictive, as some foods are limited or restricted.
The good news? Research indicates that specific food processing techniques can actually lower the FODMAP content of foods, making some of them more tolerable for those with sensitive digestive systems (1). This means that with the right strategies, you may be able to safely enjoy foods you thought were off-limits. In this article, I’ll walk you through five evidence-based ways to reduce FODMAPs using everyday cooking and preparation methods. You’ll learn how boiling, straining, fermenting, and other processes change the way foods affect your gut. And how you can apply these techniques in your own kitchen to expand your diet without sacrificing comfort.
Quick Overview of FODMAPs & IBS
FODMAPs are a group of fermentable carbohydrates (including lactose, fructans, GOS, excess fructose, and polyols) that can be difficult for some people with IBS to digest. When they aren’t absorbed well, they draw water into the gut and are rapidly fermented by bacteria, which can lead to bloating, gas, abdominal pain, and changes in bowel habits.
The low-FODMAP diet has been shown to reduce symptoms in about 3 out of 4 people with IBS. It’s usually followed in three phases – elimination, reintroduction, and personalization. I’ve outlined in detail how the FODMAP protocol works in this article: How the FODMAP Diet Works – Step 1: The Elimination Phase.
For today, what’s most important to know is that food preparation and processing methods can change FODMAP levels, sometimes lowering them enough to make a food more tolerable. Let’s look at five practical ways you can use this to your advantage.
5 Ways to Lower the FODMAP Content of Foods
1. Boiling and straining
I am often asked by my clients whether cooking reduces FODMAPs or how to make lentils and beans low FODMAP. To answer this question, I explain that one key feature of FODMAPs is that they are water-soluble, meaning they can leach into the cooking water when boiled.
Research shows that boiling dried red lentils or kidney beans progressively lowers their FODMAP content, with reductions occurring every 5 minutes up to 30 minutes. Straining the beans and lentils after boiling removes even more FODMAPs, making them easier to tolerate.
Canned legumes take this process a step further. While sitting in the liquid in the can, chickpeas, beans, and lentils continue to release FODMAPs, which is why canned varieties are often lower in FODMAPs than freshly cooked dried beans.
Dietitian Tip: During the elimination phase, choose canned legumes rated “green” by the Monash FODMAP App, such as chickpeas and lentils. After completing the GOS challenge, you can gradually experiment with cooking other dried beans and lentils to see which ones you tolerate best
2. Pressing and straining
This technique is most relevant when it comes to tofu. Firm and extra-firm tofu is made by coagulating soy milk and then pressing and straining out the liquid, which removes most of the FODMAPs. In contrast, silken tofu is coagulated in its package, so all the liquid – and the FODMAPs – remain.
Dietitian Tip: Choose firm or extra-firm tofu, drain it from the packaging liquid, and pat it dry before cooking or adding to recipes for a lower-FODMAP option.
3. Fermentation
This is where things get tricky: depending on the food, fermentation can either lower or increase the FODMAP content. For example, you may know that the low FODMAP diet mostly excludes wheat, as it is high in FODMAPs. However, when making sourdough bread, the microorganisms in the culture feed on the FODMAPs and lower the overall FODMAP content of the bread.
On the other hand, fermenting raw cabbage to make sauerkraut or kimchi increases the content of the polyol mannitol, as this is a by-product of the fermentation.
Dietitian Tip: If you want to enjoy wheat bread while on a low FODMAP diet, you can have small amounts of authentic sourdough bread. However, limit sauerkraut and kimchi to very small portions, unless you have passed the mannitol challenge, and enjoy small quantities of regular cabbage.
4. Pickling
This research showed that pickling onions, garlic, and beets reduced the FODMAP content by more than 80%. This was enough to make onions and beets “green”- rated foods. This is due to the fermentation that occurs when vegetables are immersed in brine, or to the lowering of the pH when they are immersed in vinegar.
Dietitian Tip: If you miss these vegetables, buy pickled varieties and check out the Monash University FODMAP App for appropriate serving sizes.
5. Activating (a.k.a. Soaking)
This mostly pertains to nuts. Activating involves soaking the nuts in water for a minimum of 12 hours, then dehydrating them at low temperatures. The research showed that activated cashews and pistachios (high in FODMAPs) had significantly lower FODMAP content than their raw counterpart. This happened possibly because the FODMAPs leached out in the water. Unfortunately, the reduction in FODMAP content was not sufficient to rate them “green” at a standard serving. However, a very small serving of activated cashews was rated green.
Dietitian Tip: Buying activated nuts such as almonds, which are low in FODMAP at small serving sizes, may allow you to eat more of them. After you have reintroduced FODMAPs, you can experiment and possibly increase the variety and quantity of nuts you can enjoy.
Quick Reference: How Processing Affects FODMAPs
Here’s a quick overview you can save or screenshot for easy reference when planning your meals:
| Technique | How It Affects FODMAPs | Best Examples | Dietitian Tip |
|---|---|---|---|
| Boiling & Straining | Water-soluble FODMAPs leach into cooking water | Legumes (chickpeas, lentils, kidney beans) | Use canned or soak & boil dried beans; always drain well and rinse |
| Pressing & Straining | Removes FODMAP-rich liquid | Firm/extra-firm tofu | Drain and pat dry before cooking; avoid silken tofu |
| Fermentation | Can lower (bread) or raise (cabbage) FODMAPs | Sourdough bread | Choose true sourdough; choose low FODMAP servings of fermented veggies like sauerkraut and kimchi |
| Pickling | Significantly lowers FODMAP content | Onions, garlic, beets | Use pickled forms in safe serving sizes |
| Activating (Soaking Nuts) | Can reduce but not fully eliminate FODMAPs | Almonds, cashews | Try activated almonds or cashews; keep portions small |
To Wrap It All Up!
Managing IBS is about more than just avoiding “trigger foods”. It’s about finding ways to nourish your body while still enjoying the pleasure of eating.
As you’ve seen, choosing selected canned legumes, buying firm tofu and pressing it to discard the liquid, and opting for sourdough bread and pickled vegetables or activated nuts, can make a significant difference in how well you tolerate certain foods. These strategies don’t just reduce symptoms; they also help you reintroduce variety and balance back into your diet.
Remember, everyone’s tolerance is unique. What works for one person may not work for another, which is why it’s so important to track your symptoms, experiment carefully, and seek guidance from a FODMAP-trained dietitian.
Working with a registered dietitian like me, with years of experience helping people with IBS eat a wide variety of foods without gut symptoms, can help you identify which foods are triggering your IBS and regain control of your life.
If you want to learn more about how I can help you find relief from bloating, abdominal pain, and unpredictable bowel movements, reintroduce more foods into your diet, and feel good at the same time, book your complimentary IBS Clarity Session.
We will review your symptoms and history and discuss the best next steps for you! You will come out of this call feeling relieved and hopeful that you can take control of your IBS.
Let’s work together
Book a free IBS Clarity Call today!
Published September 25, 2018. Updated, August 25, 2025.
P.S. Thanks to all my readers! Feedspot selected my blog as one of the Top 50 Low Fodmap Blogs on the web. This is the most comprehensive list of Top 50 Low Fodmap Blogs on the internet.
Antonella Dewell, MS, RDN | IBS Resolution Expert
Antonella Dewell is a registered dietitian and IBS specialist based in California. She has over 2 decades of experience working in clinical research at Stanford. Since 2018, she has been running a private practice. She helps people with IBS gain real, lasting relief from IBS symptoms in just 2-4 weeks without giving up all the foods they love, so they can stop feeling anxious around food and get back to fully enjoying food and life again.
