Tryptophan is an essential amino acid found in many protein-based foods and dietary proteins including meats, dairy, fruits, and seeds. High-glycemic index (GI) foods also increase the availability of tryptophan, which has an essential role in protein formation and as a precursor for serotonin, a neurotransmitter linked to parts of the brain responsible for controlling mood, appetite, sexual desire and performance, sleep, memory, learning, social interactions and temperature regulation; and kynurenine, part of the metabolic pathway associated with depression and inflammation when dysfunctional.
Tryptophan is involved in mood control, memory, and learning
For central serotonin production to occur, tryptophan first needs to gain access to the central nervous system (CNS) via the blood-brain barrier. Then, via hydroxylation and decarboxylation processes, serotonin is received by receptors in various brain structures, including the hippocampus, amygdala, hypothalamus, thalamus, neocortex, and basal ganglia. These systems play a role in mood improvement, abilities that involve a high cognitive demand, including memory, learning, and executive function.
Previous studies showed that depletion of central tryptophan inhibits serotonin production, caused abnormalities in mood control and depressive relapse in remitted depressed patients. Impairment of psychomotor processing, declarative memory, working memory, executive functions, and attention was also found.
Tryptophan is an essential dietary component
So, what does this mean in simple, practical terms? Because of tryptophan’s role in the synthesis of brain serotonin and, as a result, the control of moods and cognitive functioning, it is an essential component of the human diet. Tryptophan is an essential amino acid that our bodies cannot produce and must be consumed as part of our nutrition. Research suggests that most adults acquire sufficient amounts of tryptophan per day through their diets but individuals who restrict calories, exercise a lot or notice signs of moodiness, irritability, fatigue, and trouble sleeping well could benefit from increasing their consumption of tryptophan-containing foods or tryptophan supplementation.
Tryptophan is present in most protein-based foods, and particularly plentiful in oats (0.23g/100g), cottage cheese (0.32g/100g), red meat (0.23g/100g), eggs (0.17g/100g), fish (0.70g/100g), poultry (0.24g/100g), sesame (0.37g/100g), chickpeas (0.19g/100g), sunflower seeds (0.30g/100g), spirulina (0.93g/100g), and cheddar cheese (0.32g/100g).
Link to the primary research paper
Jenkins, T. A., Nguyen, J. C. D., Polglaze, K. E., & Bertrand, P. P. (2016). Influence of tryptophan and serotonin on mood and cognition with a possible role of the gut-brain axis. Nutrients, 8(1), 56-70. DOI: 10.3390/nu8010056