What is mannitol? And how does it affect people with IBS?

Are you feeling overwhelmed by the complexities of managing your Irritable Bowel Syndrome (IBS) through the low FODMAP diet?

If so, you’re not alone. In this blog post, we’ll unravel challenge of the low FODMAP diet, in particular mannitol.  As your dedicated IBS nutritionist, I help people with IBS eat a broader diet, with as many foods as you can tolerate, so you can enjoy eating again. 

Foods high in mannitol. Picture of cauliflower, mushrooms, fennel, celery, sweet potato and butternut squash.

Understanding Mannitol

Mannitol is very similar to Sorbitol (and you can read more about the FODMAP sorbitol here), in that it is very poorly absorbed into our cells, and travels through the gut. 

When you eat vegetables or any processed food containing mannitol about 75 percent of it is not absorbed. So it reaches the large intestine. And there, it is used to create short chain fatty acids, particularly butyrate, which are very helpful for the health of your colon.

Other fermentable polyols, like sorbitol, include maltitol, xylitol, and isomalt.

What foods are high in mannitol?

Well, it includes quite a few – butternut squash, cauliflower, mangetout, sweet potatoes, sauerkraut and mushrooms, as well as the food additive E421.

If you need to stay at low levels of mannitol, all of the portions of these foods should be kept at a low FODMAP level (see below for the exact amounts).

How Mannitol Impacts Digestion

As a polyol, mannitol can be natural laxative in higher doses. It draws water into the small intestine. This can lead to increased stool volume, diarrhoea, bloating, and gas.

People with IBS often have visceral hypersensitivity which means you’ll be sensitive to changes like this in the passing of gas, food and extra liquid through the gut.

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How to reintroduce mannitol to your IBS diet

Once you’ve established a good baseline on the restriction phase low FODMAP diet, the next step is a strategic reintroduction process.

All the FODMAPs should be tackled separately.

An easy FODMAP reintroduction plan

In order to bring back in any of the FODMAPs your basic process is

  • Select a food from the FODMAP group – this could be the one you’ve missed the most, or the one you think will be easiest to bring back in. It doesn’t really matter.
  • There are specific amounts to test each FODMAP. However, the basic process is firstly trial a small amount on Day 1, increase slightly on Day 2, then increase further on Day 3.
  • It’s important to monitor your symptoms as you go, and if possible write them down so you don’t forget.

For more information on reintroducing FODMAPs listen to my podcast – Episode 18.

If a high mannitol food triggers a reaction (like mushrooms), you’ll need to

  1. firstly, allow time for recovery so you get back to that baseline again with a happier digestion.
  2. then retest with a different mannitol food from the list.
  3. OR move onto the next FODMAP group and revisit mannitol later in the challenge process.

This targeted approach helps pinpoint specific triggers within the polyol category of the FODMAPs.

A reaction to one food in this group won’t necessarily mean all of them are out. This is because other compounds in foods can also affect your digestion. For example, some people find the histamine content of mushrooms a problem, but the FODMAP element isn’t an issue.

Understanding portion sizes

Managing sorbitol intake effectively starts with being mindful of portion sizes.

Let’s break down specific mannitol levels in common foods. This data is taken from the Monash University FODMAP app as of November 2023.

Foods turn to moderate or high FODMAP at these levels:

  • Butternut squash – 60g (also high in GOS)
  • Cauliflower – 75g
  • Mange tout – 25g (these are also high in fructans)
  • Sweet potato – 75g
  • Saurkraut – 30g
  • Mushrooms – button – 10g , portobello – 15g, Shitake – 15g
  • Food additive – E-421
Foods high in mannitol. Picture of cauliflower, mushrooms, fennel, celery, sweet potato and butternut squash.

Beware of FODMAP Stacking

Don’t fall into the FODMAP stacking trap. This is where you think you’re staying low FODMAP, but accidentally eat more than you realise.  

Consuming multiple low to moderate mannitol portions in a single meal can lead to bloating or gas. This is because lots of moderate portions of can add to up a higher FODMAP meal.

Read more about troubleshooting the low FODMAP diet.

Stay aware of FODMAP stacking to ensure you remain within safe limits for each meal.  Don’t panic – if you do get a reaction, just take a little break, reset your digestion and try again.

The future IBS diet

Remember, reacting to mannitol doesn’t mean omitting these foods forever.

I suggest all my Gut Reset client start incorporating small portions of low FODMAP foods, you can reintroduce variety into your diet. With mannitol this could look like sweet potato chips alongside your protein with a salad, or a small amount of mushrooms now and again.

If you got a reaction during the reintroduction

Experiment with mannitol challenges over time because tolerance to foods can change over time. You might find eating these foods are fine if you have a smaller portion, or it could be that you will be ok eating these foods on alternate days rather than every day. 

In summary

FODMAPs can be tricky to understand, but it’s easier when you have meal plans, recipes, clear instructions on how to reintroduce and symptom trackers. Sounds good? 

I specialise in working with people who have IBS, and I’m here to support you to find the best diet you can, with the most diverse foods you can tolerate. 

If you want help figuring out your IBS triggers, start your Gut Reset with me over 3 months to find a diet that works for you. Just set up a free call to discuss what you need some help with. Email info@goodnessme-nutrition.com

Hi I'm Anna Mapson, registered Nutritional Therapist.

I help people with IBS and SIBO get control of unpredictable gut symptoms to find long term relief from painful and embarrassing IBS without restrictive dieting.

I can help you to:

  • understand your digestion better, so you recognise your triggers
  • eat a well balanced diet, with tasty meals that are simple to prepare
  • develop better digestion and more energy

Find more about my 3 month 1:1 Gut Reset programme

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