Neurotransmitters are classified as either excitatory or inhibitory and each play a different role. Acetylcholine, glutamate, histamine, epinephrine, and norepinephrine are classified as excitatory, while GABA and serotonin are classified as inhibitory neurotransmitters. Dopamine is both excitatory and inhibitory.2
Excitatory neurotransmitters stimulate a cell into action, while inhibitory neurons prevents an action potential. For example acetylcholine stimulates muscle contraction, while GABA inhibits involuntary movement.2
Functions of neurotransmitters
As alluded to above, different neurotransmitters play different roles (see Table 1) and disruption in the balance between excitatory and inhibitory neurotransmitters has been implicated in the development of certain diseases and disorders.2,3
Table 1: The functions of neurotransmitters2,4,5
Can the balance in neurotransmitters be restored?
The brain requires a constant supply of ‘fuel’, which comes from dietary sources – thus what you eat directly affects the structure and function of your brain.6
Several dietary components have been identified as having effects the brain’s cognitive abilities (see Table 2). Dietary components play a role in regulating neurotransmitter pathways, synaptic transmission, membrane fluidity and signal-transduction pathways.7
Table 2: Dietary sources of neurotransmitters7,9
Unfortunately, few of us get the daily nutrients to sustain a healthy lifestyle, and by extension a healthy brain. To fill this gap, nootropics or so-called smart drugs have been developed that contain well-known compounds or supplements that enhance cognitive performance, protect the brain from toxins and minimise the effects of brain ageing.10
Nootropic is defined as a compound that increases mental functions including memory, motivation, concentration, and attention. Some nootropics can be found in in plants and foods (see Table 2), while others may be scientifically developed in a lab.10
A number of nootropic supplementations are available that combine the benefits of natural dietary sources and other proven brain boosting elements.10,11,12,13,14
Examples include supplementations that contain:
- Ginkgo biloba:Have neuroprotective effects and has been suggested as a potential treatment for Alzheimer's disease patient or other cognitive disorders. Ginkgo biloba is also listed as beneficial as an antidementia agent. It acts as an antioxidant and antiapoptotic.10
- Ginseng: Often described as ‘King Herb’. Numerous reports have been published confirming the benefits of ginsengespecially in improving the cognition function of Alzheimer's disease patients. In healthy individuals, P. ginseng has been shown to improve memory.10
- Rhodiola rosea: Also known as ‘golden root’ has been shown to improve cognitive function, enhance memory and learning, and protect the brain. It has been shown to increase levels of L-5-hydroxytryptophan (5-HT) and norepinephrine in the cerebral, prefrontal, and frontal cortex and at the same time stimulate the upregulation of dopamine and acetylcholine in the limbic system. Studies have also shown that rosea may protect the CNS against oxidative damage, thus lowering the risk of Alzheimer's disease onset, and enhances learning and memory impairment in these patients. Furthermore, both P. ginseng and R. rosea ‘adaptogen’, which means it has the ability to protect against stress. Salidroside, an active component of R. rosea has been shown to have neuroprotective and antioxidative effects.10
- 5-HT: Is produced from tryptophan by tryptophan hydroxylase and its decarboxylation yields serotonin, a monoamine neurotransmitter involved in the modulation of mood, cognition, reward, learning, memory, sleep, and numerous other physiological processes. 5-HT is further transformed to melatonin, the hormone primarily released by the pineal gland that regulates the sleep–wake cycle.12
- Magnesium glycinate: Essential for regulation of muscle contraction (including that of the heart), blood pressure, insulin metabolism, and is required for the synthesis of DNA, RNA, and proteins. In the CNS, magnesium is important for optimal nerve transmission and neuromuscular coordination, as well as serving to protect against excitotoxicity (excessive excitation leading to cell death).12
- L-theanine: A naturally occurring non-proteinogenic amino acid. The main benefits of L-theanine are associated with promoting a relaxed state without causing drowsiness. L-theanine may also have mild cognitive-enhancing effects, especially when taken with caffeine. Though it does not provide any sedative-like effects, L-theanine enhances sleep quality by promoting a more relaxed state in the brain.13
- L-Tyrosine: An amino acid found in the diet that is metabolised to produce catecholamines such as dopamine and norepinephrine. The main benefits of L-tyrosine are related to its ability to replenish catecholamine levels in the brain, which can become depleted under stressful conditions. Multiple studies have demonstrated that L-tyrosine can help to prevent declined cognitive function under stressful, cognitively demanding conditions. Although it has not been shown to improve memory under resting conditions, L-tyrosine supplementation has been shown to alleviate reduced memory under acutely stressful conditions.14
- Vitamin D3: A lipid soluble vitamin, also known as sunshine vitamin. vitamin D was reported to modulate the biosynthesis of neurotransmitters and neurotrophic factors. Vitamin D receptors are widespread in brain tissue, and vitamin D's biologically active form (1,25(OH)(2)D3) has shown neuroprotective effects including the clearance of amyloid plaques, a hallmark of Alzheimer's disease. Recent studies have confirmed an association between cognitive impairment, dementia, and vitamin D deficiency.15
- Sheffler ZM, Reddy V ad Pillarisetty LS. Physiology, Neurotransmitters. 2022 May 8. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan–. PMID: 30969716.
- Vaskovic J. Neurotransmitters . https://www.kenhub.com/en/library/anatomy/neurotransmitters
- De Leon AS and Tadi P. Biochemistry, Gamma Aminobutyric Acid. [Updated 2022 May 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPears Publishing; 2022 Jan-. PMID: 31869147.
- Cleveland Clinic. Epinephrine (Adrenaline). https://my.clevelandclinic.org/health/articles/22611-epinephrine-adrenaline
- Passani BM, Panula P and Lin J-S. Histamine in the brain. Front Syst Neurosci, 2014.
- Selhub E. Nutritional psychiatry: Your brain on food. Harvard Health Block.https://www.health.harvard.edu/blog/nutritional-psychiatry-your-brain-on-food-201511168626
- Briguglio M, Dell'Osso B, Panzica G, et al. Dietary Neurotransmitters: A Narrative Review on Current Knowledge. Nutrients, 2018.
- Gómez-Pinilla F. Brain foods: the effects of nutrients on brain function. Nat Rev Neurosci, 2008.
- Minich D. Eating for Your Neurotransmitters. https://deannaminich.com/eating-for-your-neurotransmitters/
- Suliman NA, Mat Taib CN, Mohd Moklas MA, et al. Establishing Natural Nootropics: Recent Molecular Enhancement Influenced by Natural Nootropic. Evid Based Complement Alternat Med. 2016
- Maffei ME. 5-Hydroxytryptophan (5-HTP): Natural Occurrence, Analysis, Biosynthesis, Biotechnology, Physiology and Toxicology. Int J Mol Sci, 2020.
- Kirkland AE, Sarlo GL, Holton KF. The Role of Magnesium in Neurological Disorders. Nutrients, 2018.
- Willis B. https://examine.com/supplements/theanine/
- Willis B. L-Tyrosine. https://examine.com/supplements/l-tyrosine/.
- Anjum I, Jaffery SS, Fayyaz M, Samoo Z, Anjum S. The Role of Vitamin D in Brain Health: A Mini Literature Review. Cureus, 2018.