Dopamine is a neurotransmitter found in the mammalian brain, where it controls a variety of functions, both centrally within the brain, as well as peripherally, such as cardiovascular and gastrointestinal functioning. The dopaminergic system has become most widely known for its role in several pathological conditions, including Parkinson's disease and schizophrenia. As of 2011, research is uncovering what dietary nutritional compounds can be used to modulate the dopaminergic system so as to sufficiently treat these conditions in which dopamine release and utilization is clearly dysfunctional. Some of these nutritional compounds of interest include sugar, several amino acids and dietary fatty acids.
Dietary Fatty Acids
Research published in "The Journal of Neuroscience" in 2010 noted that certain fatty-acid binding proteins were well expressed in the mature brain and are crucial intermediaries in the incorporation of fatty acids, namely arachidonic acid into the brain and heart cells. They found that heart-fatty acid binding protein partnered with the dopamine 2 receptor (D2R) in dopamine uptake. Mice absent of this particular fatty acid binding protein experienced significant withdrawal symptoms indicative of D2R dysfunction. An additional study published in the "European Journal of Pharmacology" in 2003 revealed that higher concentrations of arachidonic acid, or greater dietary consumption of its precursor, omega-6 fatty acids, lead to an inhibitory effect of dopamine uptake. Lower concentrations of arachidonic acid, it should be noted, had a stimulatory effect on dopamine uptake. Such bifurcated results suggest that consumption of dietary fatty acids, and the ratio therein, is influential in neurotransmission.
Relevant Amino Acids
Research published in "The American Journal of Psychiatry" in 2003 noted that amino acid depletion in healthy, male volunteers was directly associated with a reduction in dopamine concentrations in the brain. Researchers manipulated the diet of these healthy volunteers; as one group received an amino acid drink, including the amino acids tyrosine and phenylalanine, the other group received the exact same drink without these two amino acids. Using a binding template to reveal dopamine concentrations, the researchers found a significant increase in the dopamine concentration of those subjects who consumed the amino acid drink laced with the tyrosine and phenylalanine. These results support the idea that dietary manipulation can ultimately affect extracellular dopamine levels and may be useful in the treatment of neuropsychiatric disorders.
Sugar and Dopamine Levels
Researchers at the National Institutes of Health reported in the "Neuroscience & Biobehavioral Review Report" in 2008 that intermittent dietary sugar consumption alters extracellular dopamine in the brain, much in the way an addictive drug does. Moreover, when this intermittent sugar consumption ceases, dopamine levels are affected and signs of withdrawal can become evident. Not only can extracellular dopamine levels be affected but so too can the dopamine receptors themselves.
Sugar and Dopamine Receptors
Princeton University scientists concluded in "Neuroreport" in 2001 that intermittent dietary sugar consumption among rats up-regulated D1 receptor binding in the brain. Interestingly, D2 receptor binding in the striatum was negatively affected by increased sugar consumption. This may speak to the synergistic surveillance within the dopaminergic system, a regulatory mechanism perhaps absent in the pathological conditions mentioned previously.
References
- Chen, N. et al. European Journal of Pharmacology. Inhibition by arachidonic acid and other fatty acids of dopamine uptake at the human dopamine transporter. 2003; 478, 89-95.
- Shioda, N. Journal of Neuroscience. Heart-Type Fatty Acid Binding Protein Regulates Dopamine D2 Receptor Function in Mouse Brain. 2010; 30, 3146-3155.
- Montgomery, AJ et al. Reduction of Brain Dopamine Concentration With Dietary Tyrosine Plus Phenylalanine Depletion: A [11C]raclopride PET Study. American Journal of Psychiatry; 160, 1887-1889.
- Colantuoni C et al. Excessive sugar intake alters binding to dopamine and mu-opioid receptors in the brain. Neuroreport. 2001;12:3549--3552
- Avena, N. et al. Evidence of sugar addiction: Behavioral and Neurochemical Effects of Intermittent, Excessive Sugar Intake. Neuroscience and Biobehavioral Review. 2008; 32, 20-39.
