Breath Testing – Is It All It’s Hyped Up To Be?

Posted on March 24, 2021

Breath testing (no, not the one that determines whether or not you’ve had a few too many wines) is a tool that can be used to diagnose malabsorption of carbohydrates – specifically fructose, lactose and sorbitol. It is only available for these three sugars as the remaining FODMAPs (fructans and galacto-oligosaccharides – both under the ‘O’ in FODMAP) are poorly absorbed in everyone – meaning breath testing for all FODMAPs would be a rather pointless (and unnecessarily expensive) investment!

Breath testing is one of the less invasive and more comfortable tests that people with IBS may undergo to pinpoint what exact FODMAPs trigger their tummy troubles. Despite its benefits, breath testing isn’t necessarily a foolproof FODMAP diagnostic method – and on today’s blog we’ll discover why.

How does breath testing work?

When people with IBS consume high FODMAP foods, the carbohydrates in the foods are poorly absorbed in the small intestine and continue on to the large intestine, where they are fermented by gut bacteria. This fermentation process produces gases known as hydrogen and methane. These gases dissolve into the blood and are transported to the lungs, where they are eventually excreted through your breath.

Breath testing involves drinking a sugary drink (made with either fructose, lactose or sorbitol) and exhaling into a little machine which measures the amount of hydrogen and/or methane on your breath. The monitoring process can continue for up to 3 hours and the readings produced by the machine can give a good indication of how well or how poorly your body absorbs whichever carbohydrate you are testing. A substantial rise in breath hydrogen (or methane) following consumption of the sugar drink indicates malabsorption of the carbohydrate being tested.

To increase the accuracy of results, it’s important to be following a low FODMAP diet in the lead-up to testing and to fast for a short period beforehand. This gives an accurate baseline reading so that all numbers recorded following consumption of the sugar drink are based on the gases produced from the test drink alone.

Following diagnosis of carbohydrate malabsorption, individuals will likely see a Dietitian to work through some food challenges to confirm the diagnosis. Together, the individual and their Dietitian can work towards dietary variety and enjoyment whilst minimising IBS symptoms by being mindful of trigger foods.

Benefits of breath testing

The benefits of breath testing make it appear to be quite the miracle for those with IBS. Breath testing is:

  • Non-invasive
  • Painless
  • Relatively non time-consuming
  • A simple way to determine specific carbohydrate malabsorption

What about the limitations?

Despite its benefits, breath testing doesn’t come without its issues. Firstly, it can be fairly expensive – at roughly $100 AUD per test, breath testing can be costly. This cost can add up further if you wish to test for numerous sugars across a few days or weeks.

Like any testing, many factors can influence results of breath testing – some individuals do not reproduce hydrogen or methane. This means that testing is not always going to be 100% accurate for these individuals, for example a false negative.

Those going for testing are required to follow the instructions from the testing clinic regarding the low FODMAP diet, as diet can influence results. FODMAP Friendly certified foods are suitable to consume on the low FODMAP diet prior to breath testing


Where can I find out more?

For more on breath testing, check out Stream Diagnostics Online.  Stream Diagnostics have great resources and also test for lactulose, sucrose, mannitol and SIBO (Small Intestine Bacterial Overgrowth).  When choosing a testing clinic, ensure they test for hydrogen and methane for a more accurate test.  Some clinics do not do this.  Stream Diagnostics absolutely test for methane and hydrogen.

In summary

In summary, breath testing should only be used as a screening tool to highlight potential malabsorption of FODMAPs including fructose, lactose and sorbitol. Despite being a non-invasive and relatively simple way to determine potential IBS triggers, we wouldn’t recommend that those with IBS rely solely on this method. As always, we recommend that low FODAMAPPERS work with a FODMAP-trained Dietitian for support and guidance when dealing with IBS and following a low FODMAP diet.

Written by: Amy Lilly (Student Dietitian)
Reviewed by: Kiarra Martindale (Accredited Practising Dietitian)

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