Dopamine is a nitrogen-containing molecule that belongs to a class of chemicals called catecholamines. It's related to epinephrine, or adrenalin, and norepinephrine. In humans, dopamine functions as a neurotransmitter and a neurohormone, carrying electrical and chemical messages throughout your nervous system, bloodstream and immune system. Certain medical conditions and behaviors can deplete your levels of dopamine. A review of dopamine's biosynthesis and functions, as well as possible causes of dopamine depletion, can help you optimize your dopamine levels.
Dopamine Synthesis
Dopamine is produced from tyrosine, a non-essential amino acid that's manufactured from phenylalanine, an essential amino acid. Tyrosine is converted to dopamine in two metabolic steps, mirroring the conversion of L-tryptophan to serotonin, which is another neurotransmitter. In fact, the last step in each of these metabolic pathways is accomplished by the same enzyme. This has implications for people taking supplements to increase neurotransmitter levels.
Dopamine's Roles
Dopamine functions primarily as a neurotransmitter, relaying nervous impulses across the microscopic gaps, or synapses, that separate your neurons. This function is essential for propagating messages through your nervous system. Dopamine participates in a wide array of neurological processes, including voluntary movement, perception of reward and punishment, learning and memory, libido, motivation, attention, aggression, sleep cycles and mood. As a neurohormone, dopamine controls the release of other hormones, including prolactin, a hormone that promotes lactation, and growth hormone. Finally, dopamine modulates immune activity and regulates blood flow to various organs.
Dopamine Depletion
The classic clinical example of dopamine deficiency is Parkinson's disease, a disorder characterized by tremors and difficulty initiating voluntary movements. Insufficient dopamine or a blunted response to its effects has been implicated in other conditions as well. For example, a 2005 Behavioral and Brain Sciences article discusses a potential link between deficient dopamine pathways and attention-deficit/hyperactivity disorder. Low dopamine levels have also been associated with obesity, prolonged stress, alcohol abuse and, according to Dr. Marty Hinz of NeuroResearch Clinics, inappropriate use of certain supplements such as L-tryptophan and 5-HTP.
Boosting Dopamine Levels
Because dopamine is synthesized from tyrosine, boosting dopamine levels would seem to be a simple matter of increasing your consumption of tyrosine-rich foods such as eggs, dairy products, fish, meat or even spirulina, a seaweed source. You could also take L-tyrosine or phenylalanine in supplement form, although phenylalanine is utilized in so many ways in your body that most of it is not used to make dopamine, and people with phenylketonuria should avoid phenylalanine. Mucuna pruriens, a commercially available Ayurvedic herb, contains a natural form of L-dopa, which is converted to dopamine. This herb is popular with weightlifters for its purported ability to stimulate growth hormone release and, subsequently, muscle development. In addition, a 2004 study published in the Journal of Neurology, Neurosurgery and Psychiatry showed that L-dopa from M. pruriens evokes benefits in patients with Parkinson's disease.
Considerations
Like so many metabolic processes in your body, the production of neurotransmitters is regulated by complex interactions between receptor levels, metabolic needs, nutritional status and other factors. The shared synthetic pathways of serotonin and dopamine make it possible to inadvertently "load" one neurotransmitter to the detriment of the other, because the enzyme that performs the final conversion in both of these pathways becomes preferentially occupied by the precursors that are present in the highest concentrations. For example, increasing your levels of dopamine's precursor, tyrosine, theoretically increases your production of dopamine, but it does so at the expense of falling serotonin levels, whose precursors must wait in line for enzymatic conversion. Likewise, increasing your consumption of L-tryptophan or 5-HTP, serotonin's precursors, tips the balance of production away from dopamine.
Recommendations
In order to boost dopamine levels or enhance its effects, eat a nutritious diet that contains adequate servings of tyrosine-containing foods. Avoid behaviors that lower dopamine levels or interfere with its effects, such as excessive alcohol or caffeine consumption or illicit drug use. Strive to maintain your ideal body weight. If stress is a significant factor in your life, seek ways to reduce its effects, including counseling. If you choose to take supplements to boost dopamine levels, keep in mind their potential for adversely affecting other neurotransmitters. If you believe you're suffering from a disease that's linked to dopamine deficiency, such as Parkinson's, seek a physician's advice before you take any supplements.
References
- "Behavioral and Brain Sciences"; A dynamic developmental theory of attention-deficit/hyperactivity disorder (adhd) predominantly hyperactive/impulsive and combined subtypes; Sagvolden T, et al.; 2005
- Neuroassist.com: Neurotransmitter depletion balance between serotonin and dopamine
- "Journal of Neurology, Neurosurgery, and Psychiatry"; Mucuna pruriens in Parkinson's disease: a double blind clinical and pharmacological study; Katzenschlager R, et al.; 2004
- Top200Foods.com: Top 200 Food Sources of Tyrosine
