Standardisation of Dietary and Medication Restrictions for Urine 5-Hydroxyindoleacetic Acid (5-HIAA) Collection

The dietary restriction advice provided by Australian clinical laboratories to patients prior to 24-hour urine collection of 5-hydroxyindoleacetic acid (5-HIAA) has not been standardised. Variation exists between the lists of foods and medications patients are requested to avoid and in the duration for which the restrictions must be applied. Furthermore, the evidence for some of these restrictions is limited or outdated. A review of current literature identified that the main foods which significantly elevate urine 5-HIAA levels are plantain, banana, walnuts, hickory nuts, pineapple, plums, tomatoes, kiwifruits and avocados. These need to be avoided for at least two days prior to and during the collection period. Alcohol should be avoided for a minimum of one day before the collection and dietary supplements containing 5-hydroxytryptophan should be avoided for at least 14 days prior. Certain medications may cause false elevations of 5-HIAA but many are dependent on the assay used. Contrary to historical recommendations, we found insufficient information to warrant restriction of eggplant/aubergine, coffee, tea, milk chocolate and vanilla.