Tyrosine, taken during exposure to stress, improves mood, decreases stress-related complaints and enhances mental performance.*1 In one study, soldiers were placed in a controlled environment, then the environment was rapidly changed to simulate 15,500 feet elevation. Those soldiers given tyrosine at the beginning of the experiment adapted much quicker to the stressful environment.*1, 7  They did both mental and physical tasks better than the placebo group.*1, 7 The tyrosine-supplemented soldiers had less muscle soreness and were more resistant to cold (15NC or 59NF).*1, 7

In another study, volunteers working at 39BF had short-term memory difficulties.8   When given 150 mg of tyrosine per 2.2 pounds of body weight, memory improved significantly in this crossover, double-blind study (22 g for a 150 lb person).*8 In a study that used a very loud noise as a stressor, researchers gave people a placebo or 100 mg of tyrosine per 2.2 pounds of body weight (15 g for a 150 lb person). The tyrosine supplements increased the level of norepinephrine and epinephrine, therefore the people who took tyrosine performed better on tests.*6 These neurotransmitters influence every cell in the body and stimulate the brain and nervous system. Alertness is increased and perception of fatigue is diminished.*6

In one study, after being awake all day, workers were given 150 mg tyrosine per 2.2 pounds of body weight or a placebo before working a night shift. Those workers who had tyrosine handled tasks better and with fewer errors.*2

Tyrosine is a non-essential aromatic amino acid that is made in the body from phenylalanine using niacin and glutamic acid. Important neurotransmitters are also made in the body from tyrosine, assisted by iron, copper, vitamins B-6 and C, and methionine.

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References

Banderet LE and Lieberman HR. Treatment with Tyrosine, a Neurotransmitter Precursor, Reduces Environmental Stress in Humans. Brain Res Bull 1989;22(4):759-62.                     

Neri DF, Wiegmann D, Stanny RR, Shappell SA, McCardie A, McKay DL. The effects of tyrosine on cognitive performance during extended wakefulness. Avait Space Environ Med 1995;66(4):313-9.

Menkes DB, Coates DC, Fawcett JP. Acute tryptophan depletion aggravates premenstrual syndrome. J Affect Disord 1994;32(1):37-44.

Harper’s Review of Biochemistry, 19th edition, 1983.

Lehnert H, Reinstein DK, Strowbridge BW, Wurtman RJ. Neurochemical and Behavioral Consequences of Acute, Uncontrollable Stress: Effects of Dietary Tyrosine. Brain Res 1984;303(2):215-23.

Deijen JB and Orlebeke JF.  Effect of Tyrosine on Cognitive Function and Blood Pressure Under Stress. Brain Res Bull 1994;33(3):319-23.               

Salter, MAJ Charles A. MS USA Dietary tyrosine as an Aid to     Stress Resistance among Troops. Mil Med 1989;154(3):144-6.

Shurtleff D, Thomas JR, Schrot J, Kowalski K and Harford R. Tyrosine Reverses a Cold-Induced Working Memory Deficit in Humans. Pharmacol Biochem Behav 1994;47(4):935-41.

Maes M, Claes M, Schotte C, Delbeke L, Jacquemyn Y, Verkerk R, De Meester I and Scharpé S. Disturbances in Dexamethasone suppression test and loser availability of L-Tryptophan and Tyrosine in early puerperium and in women under contraceptive therapy. J Psychosom Res 1992;36(2):191-7.

Møller SE Effect of Oral Contraceptives on Tryptophan and Tyrosine Availability: Evidence for a Possible Contribution to Mental Depression. Neuropsychobiology 1981;7(4):192-200.