How to Test for Leaky Gut

A number of tests can help identify direct and indirect signs of a leaky gut, but no single test will give you an absolute answer.

Physicians should test when appropriate and let the results inform but not drive their clinical decisions, says Leo Galland, MD, an internist in New York City and director of the Foundation for Integrative Medicine. “I see a lot of patients who get overtested, and their health-care practitioner follows the test results blindly,” he says. As a patient, find a practitioner who you feel really listens to your experience and takes a thorough medical history.

Here are some of the most valuable tests for identifying a leaky gut:

1. Lactulose/Mannitol Test

This is the most common and only direct test of a leaky gut. The premise is simple. You ingest two types of sugar: one has large molecules (lactulose) and the other has small molecules. A healthy gut will pass the small molecules into the bloodstream to be excreted by the kidneys. The larger sugar molecules should stay in the gut. Presence of the larger molecules in the urine is indicative of a leaky gut.

2. Hydrogen Methane Breath Test

The breath test helps determine if your gut has a bacterial overgrowth. Most bacteria give off methane and hydrogen, which you expel in your breath. Presence of these gasses can indicate a serious overgrowth. Halitosis is not a sure sign of a leaky gut but it might be one indication.

3. Comprehensive Digestive Stool Analysis

This test measures how well your digestion is performing. It examines harmful bacteria growing in the gut as well as levels of candida. A practitioner can see from the results if your body is producing enough food-digesting enzymes to break down proteins, fats, and carbs for assimilation into the body.

The drawback of stool testing is that it can be an incomplete picture. Not every pathogen appears in every stool, says Leo Galland, MD, an internist in New York City and director of the Foundation for Integrative Medicine, who notes that some bacteria adhere to the inside of the gut’s lining, meaning they won’t show up in a stool test. “Stool tests are only an approximation of what’s going on inside the gut,” he says.

4. Parasitology Testing

People tend to think of this testing for world travelers, but we have plenty of parasites in the United States. They often travel in food, water, and waste. Common symptoms are belly pain, bloating, constipation, gas, itching, and joint aches. Parasites often show up in the stool but not every poop has a stowaway, and you might need to repeat the test a few times.

5. Elimination/Provocation Testing

This is a special diet that allows you to feel changes in your body by first eliminating and then reintroducing potential trigger foods. The basic approach is to eliminate the most common trigger foods (gluten, soy, dairy, nuts) for seven to 14 days and then slowly reintroduce one potentially provocative food at a time and record how you feel afterward. Did you bloat 30 minutes after eating a piece of wheat bread? Did you itch after eating peanuts? If you have a reaction, you’ve most likely found a food that irritates your gut.

6. Blood Tests for Food Sensitivities/Allergies

Identify foods you might not have thought to include in your elimination diet with this type of test. These tests look for high levels of antibodies in the blood, meaning the immune system is working overtime. Common antibody tests are IgG, IgA, and IgM.

Your intestines are home to a great deal of your digestive system, nervous system, and immune system. For more on how to heal your gut lining and avoid leaky gut syndrome, see “How to Heal a Leaky Gut,” from which this article was excerpted.

Illustrations by Kotryna Zukauskaite