The old saying, “We are what we eat,” applies when a 24-hour collection for the urine 5HIAA test is being considered. The foods that contain the precursor of 5HIAA should be avoided for at least 24 hours prior to the start of this study and during collection of urine. This fact has been know for over 3 decades.

Foods to Avoid:

  • Bananas
  • Pineapple and its juice
  • Tomatoes and all tomato products
  • Plums
  • Eggplant
  • Avocado
  • Kiwi
  • Fruits in general
  • Nuts, especially walnuts

ALL of the above contain 5-Hydroxytryptamine (serotonin).

Caffein-enriched products such as coffee, tea and colas/sodas should be avoided if catecholamines are measured (they do not contain serotonin).

It is possible to raise the baseline of one’s normal concentration of 5HIAA if the foods mentioned are consumed daily in excess. It could raise the baseline outside the normal range. How do we interpret this result? The same holds true for certain medications whether they are over-the-counter or prescriptions. They could produce interfering compounds that would affect the lab result.

Prescriptions to Avoid:

The methodology really affected by prescriptions is a colorimetric assay. Find out what technique the lab is using. There are three types: colorimetric assay, HPLC and RIA (radioimmuno assay).

  • Do not take cough and antihistamine preparations 2 days before and during the collection.
  • Thorazine and Compazine are no-no’s.
  • Nasal drops and sprays should not be used especially if the individual normally develops palpitations and sweats when these meds are used.
  • Avoid hypertension medications, Tylenol and muscle relaxants, especially prescribed for lower back pain ie: Robaxin.
  • Valium and Flexeril must be stopped 48 hours before and during the collection.

All of these could produce false high 5HIAA results.

Your next question might be, do these drugs contain serotonin? The answer is no.

The formulas for many of these compounds are normally metabolized into compounds that behave like the 5HIAA compound during the lab analysis adding additional factors that would influence the final reported result.

MAO Inhibitors:

MAO inhibitors like Nardil should be discontinued for 2 days before this test is started. There are many natural herbs bought in health food stores that  produce the same affect. Read those labels if you want an accurate result. It takes MAO (Mono amine oxidase), a specific enzyme, to convert serotonin to 5HIAA. An MAO inhibitor does just that. It prevents this pathway from operating normally. This will depress or lower 5HIAA excretion.

This information was provided by:

Francis J. DiGiorgi, MA, PhD
Serotonin Research Laboratory (1959-1998)
Mount Sinai Medical Center, New York, NY

Dr. DiGiorgi had 36 years experience measuring neuroendocrine markers related to the carcinoid syndrome and other neuroendocrine tumors.

How and Why the 5HIAA Test Is Performed, Normal Range (from Medline Plus, a service of the U.S. National Library of Medicine, National Institutes of Health)



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