Amino acid precursors of dopamine and serotonin have been administered for decades to treat a variety of clinical conditions including depression, anxiety, insomnia, obesity, and a host of other illnesses. Dietary administration of these amino acids is designed to increase dopamine and serotonin levels within the body, particularly the brain. Convincing evidence exists that these precursors normally elevate dopamine and serotonin levels within critical brain tissues and other organs. However, their effects on urinary excretion of neurotransmitters are described in few studies and the results appear equivocal. The purpose of this study was to define, as precisely as possible, the influence of both 5-hydroxytryptophan (5-HTP) and tyrosine on urinary excretion of serotonin and dopamine in a large human population consuming both 5-HTP and tyrosine. Curiously, only 5-HTP exhibited a marginal stimulatory influence on urinary serotonin excretion when 5-HTP doses were compared to urinary serotonin excretion; however, a robust relationship was observed when alterations in 5-HTP dose were compared to alterations in urinary serotonin excretion in individual patients. The data indicate three statistically discernible components to 5-HTP responses, including inverse, direct, and no relationships between urinary serotonin excretion and 5-HTP doses. The response to tyrosine was more consistent but primarily yielded an unexpected reduction in urinary dopamine excretion. These data indicate that the urinary excretion pattern of neurotransmitters after consumption of their precursors is far more complex than previously appreciated. These data on urinary neurotransmitter excretion might be relevant to understanding the effects of the precursors in other organs.

This paper analyzes the statistical correlation of urinary serotonin and dopamine data in subjects not suffering from monoamine-secreting tumors such as pheochromocytoma or carcinoid syndrome. Peer-reviewed literature and statistical analyses were searched and monoamine (serotonin and dopamine) assays defined in order to facilitate their proper interpretation. Many research findings in the literature are novel. Baseline assays completed with no monoamine precursors differ from baseline assays performed on a different day in the same subject. There is currently no scientific basis, value, or predictability in obtaining baseline monoamine assays. Urinary assays performed while taking precursors can demonstrate a lack of correlation or unexpected correlations such as inverse relationships. The only valid model for interpretation of urinary monoamine assays is the “three-phase model” which leads to predictability between monoamine assays and precursor administration in varied amounts.PurposeThis paper reviews the basic science of urinary monoamine assays. Results of statistical analysis correlating baseline and nonbaseline assays are reported and provide valid methods for interpretation of urinary serotonin and dopamine results.Patients and methodsKey scientific claims promoting the validity of the urinary neurotransmitter testing (UNT) model applications are discussed. Many of these claims were not supported by the scientific literature. Matched-pairs t-tests were performed on several groupings. Results of all statistical tests were compared with peer-reviewed literature.ResultsThe statistical analysis failed to support the UNT model. Peer-reviewed literature search failed to verify scientific clams made in support of applications of the UNT model in many cases.

This paper analyzes the statistical correlation of urinary serotonin and dopamine data in subjects not suffering from monoamine-secreting tumors such as pheochromocytoma or carcinoid syndrome. Peer-reviewed literature and statistical analyses were searched and monoamine (serotonin and dopamine) assays defined in order to facilitate their proper interpretation. Many research findings in the literature are novel. Baseline assays completed with no monoamine precursors differ from baseline assays performed on a different day in the same subject. There is currently no scientific basis, value, or predictability in obtaining baseline monoamine assays. Urinary assays performed while taking precursors can demonstrate a lack of correlation or unexpected correlations such as inverse relationships. The only valid model for interpretation of urinary monoamine assays is the "three-phase model" which leads to predictability between monoamine assays and precursor administration in varied amounts. Purpose: This paper reviews the basic science of urinary monoamine assays. Results of statistical analysis correlating baseline and nonbaseline assays are reported and provide valid methods for interpretation of urinary serotonin and dopamine results. Patients and methods: Key scientific claims promoting the validity of the urinary neurotransmitter testing (UNT) model applications are discussed. Many of these claims were not supported by the scientific literature. Matched-pairs t-tests were performed on several groupings. Results of all statistical tests were compared with peer-reviewed literature. Results: The statistical analysis failed to support the UNT model. Peer-reviewed literature search failed to verify scientific clams made in support of applications of the UNT model in many cases.

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