Evaluating GI Transit Time

Gastrointestinal transit time—the interval between consumption of food and it’s elimination as feces—is a handy indicator of digestive health, and by extension, overall health status. It is easy and inexpensive to measure, and often proves helpful in working with patients who have digestive problems.

All it takes is a willing patient and a handful of encapsulated charcoal capsules!

A transit time between 12-18 hours is considered healthy. But for all too many Americans, the transit time proves to be 36-96 hours or even longer. This is problematic because the longer the fecal material sits and putrefies in the intestines, the more likely it is that toxins will be absorbed.

Long transit times are associated with toxin reabsorbtion, poor metabolism, and a predisposition toward or amplification of many chronic intestinal or systemic illnesses.

Low intake of dietary fiber is a major factor underlying prolonged transit times in many people. Absence of fiber in the diet requires the body to work harder to ‘push’ wastes along. Clear evidence of a grossly prolonged transit time can sometimes be a strong motivator for patients to make healthful changes in their diets.

Very short transit times (under 10 hours) indicate a different type of problem. In these cases, the GI system does not have adequate time to digest and assimilate what is eaten. In these cases, the patient may be experiencing a form of malnutrition, owing to malabsorption, despite consuming large amounts of food.

A Fistful of Charcoal

Assessment of transit time is quite simple. It involves ingestion of a concentrated dose of activated charcoal—the same sort as is used for treating gas and bloating--and then tracking when the charcoal shows up in the feces.

Instruct the patient to take 6 - 12 capsules (1.5 - 3 grams of charcoal) with 8 ounces of water between meals. For most accurate results, he or she should ingest the capsules just after a bowel movement. I recommend using a high quality brand of activated charcoal such as Requa, easily obtained in most pharmacies.  

The number of capsules to take should be guided by the patient’s weight, as follows:

  • If weight is less than 150 lbs: 6 capsules
  • 150 – 200 lbs: 8 capsules
  • 200- 250 lbs: 10 capsules
  • If weight exceeds 250 lbs: 12 capsules

The patient should make sure to mark the specific time of charcoal ingestion, as this marks the start of the test. It is complete when the patient begins to notice the black, crumbly charcoal in the feces. Make sure the patient records this time, as well. The transit time is simply the difference between the two.

It is often helpful to have the patient record other features of their feces, including consistency, texture, color, uniformity (or lack thereof) and buoyancy, all of which can provide clues as to what’s happening (or not happening) in the GI tract.

The transit time measurement is a very good focus for working with patients who have digestive issues, and normalization of transit time can become a health goal that patients begin to work toward through dietary and nutraceutical approaches.  I generally recommend that they re-check transit time twice a month until a healthy transit time is achieved.

Russell Jaffe received his MD and PhD from Boston University School of Medicine in 1972. He is a founding chairman of the Scientific Committee of the American Holistic Medical Association. Dr. Jaffe developed the lymphocyte response assays (LRA) that enable physicians to rule in/out 436 common allergenic substances based on delayed hypersensitivity by functional LRA by ELISA/ACT or MELISA tests. He is also founder of Perque, a practitioner-only nutraceuticals company.