What is L-tyrosine?
tyrosine is an amino acid and the building block to your reward and pleasure chemical messenger; dopamine. Dopamine is released when you derive pleasure from sex, great food, and a sense of accomplishment. According to the Natural Medicines database, dopamine is responsible for modulating emotional states, sex drive (libido) and body movements , and the capacity to handle your everyday stress .
Who might benefit from focusing on tyrosine intake?
if you follow a vegan diet there is a chance you might want to pay closer attention to your dietary tyrosine intake. Tyrosine is found in protein-rich foods and the highest sources are found in animal-based proteins . The top plant-based sources of tyrosine are seaweed, pumpkin leaves and cooked mustard greens . A 2010 Cochrane review also found those people with a rare genetic disorder that struggle to breakdown another dietary amino acid (phenylalanine) may benefit from tyrosine supplementation 
How does tyrosine work?
tyrosine is converted into dopamine via L-DOPA  and it has been shown to release spikes of dopamine in regions of the brain centrally involved in emotional response and reinforcing behaviours . A 2015 US military clinical review on studies found that "the effects of tyrosine are found 60- 300 minutes after ingestion; plasma levels peak at about 120 minutes. Accordingly, future studies should strongly consider administering tyrosine approximately 2 hours before performance tasks" 
Alertness and motivation?
the Journal of Psychopharmacology published a study that found 5 hours post-ingestion of tyrosine increased alertness , and investigations into diets depleted in tyrosine highlighted an association between decreased dopamine synthesis and slower reaction time in phasic alertness tasks .
when you anticipate an event as well as the event itself has been shown to spike dopamine levels spike and to induce motivation and alertness. This response is important because it encourages you to act on the perceived benefit you or avoid something negative .
Dopamine and sexual libido
motivation also plays a significant role in your sexual libido. When anticipating sexual activity, erotic stimuli triggers dopamine which encourages us to seek reward. MRI scans revealed that whilst in a subconscious state, adults that looked at erotic images for 6 minutes had a surge of dopamine release and activity in reward-related brain areas .
Does tyrosine impact your stress response?
tyrosine is not a relaxant. However, there is some evidence that shows it can improve two outcomes where acute stressors are involved .
- Cognition: in short term, stressful situations, clinical reviews suggest that tyrosine may help to improve decision making when dopamine is depleted, particularly in cognitively demanding tasks . A military study revealed that cadets that consumed L tyrosine improved on their memory, tracking tasks, and cognitive performance in comparison to control . Those tasks occurred whilst they were undergoing high-intensity training and additional stressors such as heat whilst further studies have suggested the administration of tyrosine may promote convergent (deep) thinking when multitasking creative tasks .
2. Reduction in fear: Research on the administration of tyrosine measuring patient self-assessment of fear, stress, and tension was able to demonstrate that tyrosine reduced fear expression  when subjected to negative audio and visual stimuli.
Can tyrosine improve mood?
Acute tyrosine depletion studies have induced mood lowering in healthy women with mild seasonal changes to mood and behaviour  and it is believed that an imbalance of dopamine in the brain adversely affects mood. The amino acids tyrosine and 5-htp have been widely studied to test their impact on serotonin and dopamine. Dopamine is released in regions of the brain that are involved in emotional connection and mood and a 2015 study published in The Journal of Neuroscience found that “boosting dopamine increased happiness resulting from some rewards” . Trying to feel motivated, rewarded, and pleasured whilst running low on dopamine may feel like running a marathon with a broken leg to some.
Anecdotal evidence found online such as L tyrosine Reddit discussions frequently discuss high dose tyrosine  but these can cause side effects including headaches and nausea . Speak to a nutritionist or healthcare professional about tyrosine supplements and buy from reputable health food stores such as Whole Foods Market, Planet Organic or even L tyrosine from Holland and Barrett. brain feed has a 750mg natural tyrosine from fermented corn and you can read more about it here.