Let’s Talk about Mannitol & the Low FODMAP Diet

What is Mannitol?

Love sweet potato? But can’t tolerate large serves? Then you might have issues absorbing mannitol. Mannitol is a high FODMAP sugar alcohol and it belongs in the ‘Polyol’ group within the FODMAP acronym. This sneaky FODMAP occurs naturally in a range of fruits and vegetables, and it can also be manufactured and added to our food. Check out my article to find out where mannitol likes to hide.

Where is Mannitol Found?

Mannitol naturally occurs in high levels in a range of fruit and vegetables like watermelon, clingstone peaches, button mushrooms, cauliflower, celery, snow peas, butternut squash and sweet potato (1 2). It’s important to remember that many high FODMAP foods like butternut squash, sweet potato and snow peas, have smaller serves that are low FODMAP (explore the Monash Low FODMAP app for more information).

Mannitol can also be manufactured from fructose sourced from cornstarch (3). Manufactured mannitol is used as a sweetener and is added to a wide range of products from ‘sugar free’ foods and beverages, through to protein powders, baked goods, and chewing gum. It is also added to some liquid medications like cough syrups, cold medicine, and liquid pain relief.

Can Mannitol be Called Anything Else?

Check processed products for mannitol food additive number e421 or 421 (4). In the USA mannitol should be called by its full name in the ingredient list.

Why is Mannitol an Issue?

Mannitol is a polyol and only one-third of the polyols consumed are actually absorbed by our bodies. The level of absorption depends on the type of polyol and the individual. When polyols are poorly absorbed, our gut bacteria feast on the sugars and rapidly ferment them, causing IBS symptoms (1 5). Polyols are also natural laxatives, as they draw water into the large intestine when they are poorly absorbed, which stimulates bowel movements (1 5).

Do Mannitol Levels Vary Between Foods?

According to a research paper published by a Monash University research team in the Journal of Agricultural and Food Chemistry, the mannitol levels between different fruits and vegetables do vary. Below is a table with a few examples.

*These vegetables have small serves that are low FODMAP. N/A stands for ‘Not Available’.

(Information in table sourced from: Monash University App, 2016; Muir et al., 2009)

Can You Cook With Foods High In Mannitol?

During the first phase of the low FODMAP diet, make sure you avoid cooking with foods that are high in mannitol, unless they have a low FODMAP serving size (check the Monash Low FODMAP app for serving size guidelines). For example, in the low FODMAP phase you can enjoy a low FODMAP 75g serve of sweet potato. However, be careful when adding other low FODMAP serves of foods that also contain mannitol. For example, combining a full serve of butternut pumpkin and sweet potato in one meal, as this might take you over the FODMAP threshold level. Otherwise, it is recommended that you avoid cooking with foods that are high in mannitol (button mushrooms, cauliflower, clingstone peach, watermelon), instead focus on low FODMAP ingredients.

Also keep in mind that mannitol is water soluble (6), just like the fructans in onion and garlic. This means that the mannitol will leach out of the food and into the liquid in the meal. For example, if you cook a soup using button mushrooms, the mannitol will leach out of the mushroom and into your soup, raising the overall FODMAP content. Even if you pick the mushrooms out of the meal you could still consume a high FODMAP load.

Final Thoughts

Mannitol is a sugar alcohol that can sneak into our diet through certain fruits, vegetables, and processed products. Make sure you check food labels for mannitol food additive name e421. During the first phase of the low FODMAP diet, make sure you avoid foods that are high in mannitol, unless they have a safe serving size.