Both stimulatory and inhibitory effects of dietary 5-hydroxytryptophan and tyrosine are found on urinary excretion of serotonin and dopamine in a large human population

Abstract

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.

Neurotransmitter testing of the urine: a comprehensive analysis

“…3,5 These newly synthesized serotonin and dopamine molecules are then either transported out of the proximal convoluted renal tubule cells across the basolateral membrane and then into the peripheral system via the renal vein or across the apical membrane and then into the urine. [3][4][5]14,15 It is noted that there are many other renal interactions that exist between synthesis of serotonin and dopamine transported across the basolateral membrane and the apical membrane prior to arriving at the final destination of the renal vein or urine, respectively. These interactions appear small in comparison with the effects of the basolateral monoamine transporter and the apical monoamine transporter under the three-phase model.…”

“…An inverse correlation is referred to as a Phase I response. [3][4][5] Unexpected results with matched-pairs t-test analysis revealed no significant difference when comparing baseline monoamine assays with assays performed while taking supplemental amino acid precursors in the same subject.…”

“…Even though this model is relatively new, having been developed in 2003, this approach and the urinary serotonin and urinary dopamine applications developed according to this model are supported by the scientific literature, having been discussed and documented in several articles since February 2009. [3][4][5] The basis for the OCT model requires two or more serial urinary serotonin and dopamine (ie, monoamine) assays while taking varied amino acid precursor daily dosing amounts. The results are then compared in order to determine the change in urinary serotonin and dopamine levels in response to changes in dosing.…”

“…Peer-reviewed scientific publications discussing urinary serotonin and urinary dopamine phase analysis according to the OCT model were first published in 2009 3,4 and 2010. 5 These publications outlined the mechanics of the three-phase model in connection with urinary serotonin and urinary dopamine under a novel renal transporter model.…”

Urinary neurotransmitter testing: considerations of spot baseline norepinephrine and epinephrine

“…The number of days column is the number of days between urinary sample collection dates synthesized by structures in the kidneys. 1,[3][4][5]13 Spot baseline testing lacks reproducibility and is of no value in patients not suffering from a monoamine-secreting tumor. 1 Those who claim that spot baseline urinary neurotransmitter testing is valid assert that monoamines cross the blood-brain barrier, are filtered at the glomerulus, and simply excreted into the urine without further renal involvement.…”