If asked to list the reasons that protein and amino acids are important to include in our human diet, the most common associations are probably things like muscle building or body maintenance and repair. While this is very true, the amino acids that make up proteins have many important physiological roles in our bodies aside from structural ones. One of those non-structural roles that is incredibly important, is building neurotransmitters, the signals sent between neurons that keep our thoughts clear, our reactions reasonable, and our mood balanced.

How Do Amino Acids Work in the Brain?

While some neurotransmitters act as stimulants, creating excitement, sparking motor movement, promoting alertness, energy, and activity, other neurotransmitters are responsible for calming the nerves, promoting relaxation and peace in the body. Each type of neurotransmitter is made of a different combination of amino acids. When the necessary amino acids are deficient in the body, some neurotransmitters cannot be made in enough quantity to send the appropriate signals between neurons.

For example, serotonin, dopamine, and norepinephrine are well known to be important mood-regulating neurotransmitters, but they also promote healthy sleep, energy, and cognition and are even associated with pain relief. Tryptophan is converted to 5-HTP and then can be used to make serotonin [1]. The catecholamine neurotransmitters dopamine, norepinephrine, and epinephrine are all synthesized in a stepwise process, originating from the amino acid tyrosine [2]. GABA, the calming neurotransmitter, known for its anxiolytic ability to quiet the nervous system, can only be made in the body from the breakdown of the neurotransmitter glutamate, which is a product of the amino acid glutamine [2]. 

Clearly, it is not only the quantity of amino acids we consume that is important to our brain health but also the variety and diversity of amino acids.

Which Amino Acids Support My Mood?

Major depressive disorder (MDD) is a common mental disorder that affects approximately 5–20% of the world population [3]. That statistic is rather nonspecific because MDD can be difficult to diagnose, many people suffering do not self-report or reach out for support, and the causes of the disorder are not singular. We do know that when a person has been diagnosed with MDD, the typical first line of antidepressant treatment is a group of medications called selective serotonin reuptake inhibitors (SSRIs). SSRIs are also often prescribed for patients with anxiety disorders. Essentially, these drugs are focused on the availability of the neurotransmitter, serotonin. They work by slowing the breakdown of circulating serotonin, so as new serotonin is made, there will be more available at receptor sites for the communication of positive feelings. 

Supplements do not manipulate the body in the same way drugs do, but we can take cues from how our body naturally produces serotonin to make sure we are providing it with the proper nutrients in sufficient quantities to support natural neurotransmitter production.

For example, a recent scientific study reported that a group of amino acids: valine, leucine, and isoleucine, were all found to be significantly decreased in patients with major depression [4]. These aminos all use the same transport system to cross the blood-brain barrier as the other large neural amino acids (LNAAs; tyrosine, phenylalanine, threonine, methionine, and histidine) and the serotonin precursor tryptophan. The carrier protein that shuttles amino acids across the blood-brain barrier has a higher affinity to some aminos and is more likely to bind and carry leucine than tryptophan [1]. The researchers suggested that competition among these amino acids for the carrier protein might mean that when we are consuming foods with a higher ratio of other LNAA, less tryptophan may be transported to the brain, causing a decrease in serotonin synthesis [4]. Unfortunately, many foods that are known to be high in tryptophan are also high in other aminos, maintaining a ratio that does not favor tryptophan uptake by the brain. This study provides further evidence that we should pay careful attention to the types of, and balance between, the amino acids we are consuming from our diet. Supplements can help us maintain a balance not provided by the foods we eat.

While dietary supplements are never meant to treat diseases or disorders, the more we understand about the biological basis of disease, the better we can nourish our systems to protect ourselves from deficiencies or replenish our bodies when depleted. Nutritional deficiencies can manifest in a wide range of symptoms, some physical, some mental. When it comes to supporting a calm, positive mood, it follows that we should boost our diet with the amino acids that support the synthesis of neurotransmitters associated with feelings of calm and positivity.


  1. Strasser, Barbara, Johanna M. Gostner, and Dietmar Fuchs. “Mood, food, and cognition: role of tryptophan and serotonin.” Current Opinion in Clinical Nutrition & Metabolic Care 19.1 (2016): 55-61.
  2. Friedman, Mendel, and Michael R. Gumbmann. “Dietary significance of D-amino acids.” Absorption and utilization of amino acids. CRC Press, 2018. 173-190.
  3. Woo, Hye‐In, et al. “Plasma amino acid profiling in major depressive disorder treated with selective serotonin reuptake inhibitors.” CNS neuroscience & therapeutics 21.5 (2015): 417-424.
  4. Baranyi, Andreas, et al. “Branched-chain amino acids as new biomarkers of major depression-a novel neurobiology of mood disorder.” PloS one 11.8 (2016): e0160542.