Health Benefits Of Tyrosine

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Tyrosine is a hydrophobic non-essential amino acid assuming numerous biological roles in the body, the most vital perhaps being as a precursor of hormones and neurotransmitters and as a key player in the production of a variety of enzymes, proteins, and muscle tissues. Its sufficient availability in the brain is also associated with improved working memory, increased mental alertness, and better mood. [1] This is the amino acid you certainly can never forget, no pun intended! Our body can actually produce its own supply of tyrosine from phenylalanine, but a healthy intake of a number of common protein-rich foods such as cheese, soy meal, peanuts, fish, pork, chicken, and pumpkin seeds, which contain substantial amounts of tyrosine, may prove helpful in stabilizing our tyrosine levels. [2]

Tyrosine and Cognitive Performance

Over the past decades, extensive research studies have centered on the influence of tyrosine on cognition, memory, and stress, specifically on how alterations in the availability of this amino acid relates to the levels of dopamine and norepinephrine in the brain and to the prevention of cognitive decline in response to a variety of acute stressors. In a 1995 study from Naval Aerospace Medical Research Laboratory, Florida, USA, wherein study participants were asked to execute nine iterations of a range of performance tasks and mood scales for around 13 hours and to remain awake throughout the day, the intake of tyrosine significantly alleviated the usual decline in performance on psychomotor task and the reduction in lapse probability on high-event-rate vigilance task, with such improvements lasting for 3 hours. [3]

This finding wherein improved performance was observed post-tyrosine administration is in keeping with the study results of Thomas et al. (1999), who investigated the effects of tyrosine on the performance of multiple and simple tasks. Study participants were recruited to undergo a battery of tests an hour after intake of tyrosine or placebo; the multiple task tests were structured to evaluate working memory, arithmetic skills, and visual and auditory monitoring, while the simple task battery of tests measures only working memory and visual monitoring. As the results of the study indicate, tyrosine has improved accuracy and reduced the frequency of list retrieval on the working memory task as compared with placebo, with an accompanied increase in heart rate and blood pressure during the performance tasks. This goes to show that tyrosine may sustain working memory when competing requirements to carry out other tasks concurrently degrade performance. [4]

In 1999, Deijen and team similarly examined the effect of tyrosine on the cognitive task performance of cadets undertaking a demanding military combat course. In this study, half of the subjects were requested to consume five daily doses of a protein-rich drink that contained 2 grams of tyrosine. The other half were given a drink that was carbohydrate-rich drink but had the same amount of calories. The test subjects on the tyrosine-rich drink exhibited better performance on memory tasks and tracking, indicating that tyrosine supplementation may reduce the effects of stress and fatigue on cognitive task performance when one is going through conditions characterized by psychosocial and physical stress. [5]

Tyrosine and Its Biological Functions

Tyrosine occurs in proteins responsible for signal transduction processes and acts as the recipient of phosphate groups transferred through receptor tyrosine kinases. Tyrosine kinases serve as the body’s primary cell-surface receptors whose ligands are soluble or membrane-bound protein hormones such as nerve growth factor, platelet-derived growth factor, fibroblast growth factor, epidermal growth factor, and insulin and whose binding to the aforementioned ligands triggers the activity of the intrinsic protein kinase and in turn a signal-transduction cascade, resulting in alterations in cellular physiology. [6]

Tyrosine as a Precursor of Neurotransmitters and Hormones

One of the most significant roles of tyrosine is its primary involvement in the catecholamine metabolic pathway, the products of which include dopamine, norepinephrine and epinephrine. Without tyrosine, these catecholamines, which perform indispensable functions throughout the body, cannot be synthesized.

Through the action of tyrosine hydroxylase, L-tyrosine is converted into l-DOPA, which is then decarboxylated into dopamine. Depending on the cell type, dopamine may be further converted to norepinephrine and then to epinephrine, as necessary. [7] Moreover, tyrosine stands as the precursor of the thyroid hormones triiodothyronine (T3) and thyroxine (T4), of the pigment melanin, of p-coumaric acid (a major component of lignin), and of alkaloids such as morphine and mescaline.