Assessing Nutrient Absorption in the Bowel

Bomb Calorimetry Test Explained

Bomb Calorimetry Test Explained: Assessing Nutrient Absorption in the Bowel

Your doctor or dietitian has referred you for the bomb calorimetry test.

In this video, we explain what the bomb calorimetry test is and how it is performed. With this test, we examine how well your intestines absorb nutrients and whether there is any malabsorption. You will see step by step what you need to do, such as keeping a food diary and collecting stool samples. We also provide practical tips and explain what happens after the examination. This way, you will be well prepared for the test.

What is malabsorption?

The digestive tract is a long tube that runs from the mouth to the anus. It includes the esophagus, stomach, small intestine, and large intestine. Its role is to digest food and absorb nutrients into the bloodstream.

When the intestines function properly, almost all nutrients and fluids are absorbed. Sometimes this process is less effective, for example due to surgery, medication, or illness. In that case, fewer nutrients are absorbed. This is called malabsorption.

Symptoms of malabsorption may include loose stools, undigested food in the stool, weight loss, or deficiencies of vitamins and minerals.

Purpose of the bomb calorimetry test

To assess how well your intestines absorb nutrients, we analyze both:

  • your stool (in the laboratory), and
  • what you eat and drink, recorded in a food diary.

By comparing these two, we can determine how much of the nutrients your body has absorbed.

What do you need to do?

Food diary

You will keep a food diary for 4 days.

  • Write down everything you eat and drink.
  • Indicate whether products are full-fat or low-fat, for example:
    • whole milk or skimmed milk
    • regular cheese or 30+ cheese
    • regular yogurt or low-fat yogurt
  • Also indicate if a product is a “light” version.
  • Weigh all food using a kitchen scale and measure drinks with a measuring cup.
  • Do not forget small items, such as a piece of chocolate or sugar or milk in your coffee.
  • If possible, note the brand, weight, and method of preparation of each product.
  • Try to eat and drink as normally as possible, just as you usually do.

Using this food diary, we calculate your nutrient intake and compare it with what is found in your stool.

Collecting stool

You will receive one or more buckets from your doctor or dietitian.

From the second day of the food diary, collect all stools for 3 days (72 hours) in the provided bucket(s). In some cases, this period may be shorter or longer.

  • Record in the food diary how many bowel movements you collect. There is a table provided for this.
  • If you are unable to collect a stool sample at any time, write this down in the food diary.
  • Sometimes you may need to temporarily stop certain medications. Your doctor or dietitian will inform you if this applies.

Practical tips:

  • Make sure that no urine, blood, or toilet paper gets into the bucket. Urinate first, then use the bucket.
  • Keep the bucket as cool as possible (for example in the refrigerator, on a balcony, or with cooling elements) to reduce odor.
  • If the bucket becomes full before the collection period ends, use a second bucket.
  • In some cases, you may stop collecting once one bucket is full. Your doctor or dietitian will advise you.
  • Always note the start and end time of stool collection.

After completion

  • Hand in the bucket(s) at the laboratory.
  • Sometimes you will also receive small containers for additional stool samples. Fill these and hand them in as instructed.
  • Give the food diary to your dietitian, or return it using the reply envelope provided, there is no stamp required.
  • You will receive the results within a few weeks. Your doctor or dietitian will discuss them with you.
  • If needed, you will receive dietary advice or medication.

 

Questions?

Do you have any questions about the test or the preparation? Please contact your dietitian. Good luck with the test!