Food Intolerance

Hydrogen and Methane Breath Tests are used to determine intolerances to both Lactose (the sugar found in milk) and/or Fructose (the sugar found in honey and many fruits). In order to maximise the accuracy and information obtained from a breath test, the first breath test is a control test, using Lactulose (a mild laxative), which everyone will have a reaction to. The control test is done to determine whether you are a Hydrogen producer or a Methane producer to insure that the subsequent breath tests will be measuring the most appropriate gas for you.

Normally the sugars that we ingest every day are absorbed within the small bowel, but a large proportion of people absorb these sugars poorly, allowing the sugars to pass into the large bowel. When these improperly absorbed sugars react with the bacteria in the large bowel, a gas is produced, either Hydrogen or Methane, and in turn this is absorbed into the bloodstream and travels to the lungs where it is breathed out, and can be detected through these breath tests. Production of high levels of Hydrogen or Methane gas once the Lactose or Fructose sugar has been ingested suggests the sugar is not being absorbed properly in the small bowel and indicates an intolerance to that particular sugar. The breathalyser used at the MacMurray Centre only detects both Hydrogen and Methane particles.

How are Intolerance Breath Tests performed?

For the control test, the patient will be asked to give an initial blow, which will hopefully generate a number low than 10 ppm (parts per million), and then will be given the lactulose to ingest. Every 15 minutes after this, the patient will be asked to repeat the blowing process. As soon as the breathalyser generates a number 20 ppm or higher than the initial blow more than once, we know that a reaction has occurred and we conclude the test. However long it takes to elicit a reaction is known as the oro-caecal transit time (the amount of time it takes for the sugar to reach the large bowel from your mouth) and knowing the personal transit time for each patient helps us determine how much time they must stay for each subsequent test; adapting the tests specifically for each patient.

This process can take between 1-3 hours, and will be repeated using lactose and fructose. A total of three breath tests will take place, each on separate days. Feel free to bring reading material, laptop computers etc. to use throughout the morning. Occasionally people experience symptoms of abdominal discomfort, flatulence or diarrhoea during these tests. A specialist is available in the unlikely event that medical attention is necessary.


Why are Breath Tests performed?

A major purpose of breath testing is to assist the dietitian in identifying carbohydrate intolerances. To treat this they may recommend the low FODMAP diet (low in fermentable carbohydrates such as fructose, lactose, fructans, GOS, sorbitol and mannitol). While breath testing helps identify intolerance to fructose and lactose, it does not indicate degree of intolerance or tolerance to other FODMAP groups. An assessment with a dietitian is strongly recommend to provide specific advice tailored to your symptoms.

How to prepare for Breath Tests

For the breath tests to be valid, it is important that you follow these instructions concerning medications, supplements, and diet prior to each test.

Four weeks before:

Allow at least 4 weeks after the termination of any antibiotic treatment before breath test appointment.

Two weeks before:

  • No probiotics, such as IBS Support, Inner Health Plus, acidophilus or bifidobacteria powders or capsules, Yakult or VSL#3. If you are taking probiotics please make sure your breath test is booked two weeks after you have finished taking them. You may eat yoghurt (without added probiotics) until the day before each test when you are required to follow the special diet.

One week before:

Allow at least 1 week after your Colonoscopy procedure before your first Breath Test appointment

A day before:

  • Take only prescription medication for one full day before each test. Avoid taking vitamins, minerals, Yakult yogurt, fish oil, laxatives or anti-diarrhoeal agents one full day before each test unless absolutely necessary.
  • Avoid chewing gum and mints
  • Avoid protein supplements (protein powders, bars, shakes) and sports recovery drinks.
  • You may eat yoghurt until the day before each test.
  • You are required to follow the dietary instructions (see below) for 24 hours before your test.
  • Avoid vigorous physical exercise (e.g. gym session, run) for 24 hours prior to each test.
  • Fast from 8pm the night before each test. You may drink water but nothing else. If your medication needs to be taken with food, please discuss with doctor whether it can be delayed until after the test.

The morning of the test:

  • Remain nil by mouth the morning of the procedure
  • Please do not smoke
  • Avoid chewing gum and mints
  • Do not exercise on the morning of the test
  • Brush teeth with toothpaste (NOT the natural type) and rinse well. Do not use mouthwash.
  • Do not use perfume, aftershave, body lotions or scented moisturiser or makeup, unscented deodorant is ok.
  • Do not wear clothing that has been washed in fabric softener.
  • Do not wash your hair with highly scented shampoo or conditioner.
  • No sleeping or vigorous exercise for at least 1 hour before or any time during the breath test.

Once you have finished your breath tests, an assessment with a specialist dietitian is recommended.

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