samoth said:
Unless you can show me some peer-reviewed journals or studies (how does one 'test' whether a smart drug works or not?), I'd classify it as a placebo effect.
But if it seems to work well for you, more power to you!
a) absence of proof isnt proof of absence - while there are lots of studies supporting tyrosine as a cognition & concentration enhancer, keep in mind that its a non-patentable substance so its not in anyone's financial interest to fund large-scale expensive studies that will only draw customers away from expensive prescription drugs (current or future). Else there would be many more.
b) from my own use during my software development days, there's a definite effect. how do you test? either the magic works and you solve the formula, close the logic loop, unify the threads or you don't. the magical epiphanies happened better and faster and more often with tyrosine than without.
c) here's a bunch of studies
http://au.health.yahoo.com/041101/25/1uk1.html?r=967507465
REFERENCE: Thomas JR et al. Tyrosine improves working memory in a multitasking environment. Pharmacol Biochem Behav 1999 Nov;64(3):495-500
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Aviat Space Environ Med 1995 Apr;66
The effects of tyrosine on cognitive performance during extended wakefulness.
Neri DF et al.
Tyrosine, a large neutral amino acid found in dietary proteins, has received recent attention as a potential treatment for stress. The behavioral effects of tyrosine were examined during an episode of continuous nighttime work involving one night's sleep loss. Subjects performed nine iterations of a battery of performance tasks and mood scales for approximately 13 h, beginning at 1930 and ending at 0820. They remained awake throughout the day on which the experiment began and were awake for more than 24 h by the end of testing. Six hours after the experiment began, one-half of the subjects received 150 mg.kg-1 tyrosine in a split dose while the other half received cornstarch placebo in a double-blind procedure. Tyrosine administration was associated with a significant amelioration of the usual performance decline on a psychomotor task and a significant reduction in lapse probability on a high-event-rate vigilance task. The improvements lasted on the order of 3 h.
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Mil Med 1989 Mar;154(3):144-6
Dietary tyrosine as an aid to stress resistance among troops.
In past conflicts battle stress casualties have caused a serious exit of troops from the frontlines. Recent research has linked stress-caused impairments of performance with depletion of brain stores of the neurotransmitter norepinephrine (NE), which functions in neural tracts responding to stress. The amino acid tyrosine (TYR) is the dietary precursor for NE, and supplementation with TYR has been demonstrated in the laboratory to alleviate declines in both neural NE and performance during stress. Thus, TYR supplementation might help to prevent and treat stress casualties in combat. Further research is called for to verify this hypothesis.
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Brain Res Bull 1989 Apr;22(4):759-62
Treatment with tyrosine, a neurotransmitter precursor, reduces environmental stress in humans.
Banderet LE et al.
Acutely stressful situations can disrupt behavior and deplete brain norepinephrine and dopamine, catecholaminergic neurotransmitters. In animals, administration of tyrosine, a food constituent and precursor of the catecholamines, reduces these behavioral and neurochemical deficits. Using a double-blind, placebo-controlled crossover design we investigated whether tyrosine (100 mg/kg) would protect humans from some of the adverse consequences of a 4.5 hour exposure to cold and hypoxia. Tyrosine significantly decreased symptoms, adverse moods, and performance impairments in subjects who exhibited average or greater responses to these environmental conditions. These results suggest that tyrosine should be evaluated in a variety of acutely stressful situations.
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Improves cognitive performance under stressful conditions. A study looking at the effects of the amino acid tyrosine on cognitive task performance found that supplementation with tyrosine may, under operational circumstances characterized by psychosocial and physical stress, reduce the effects of stress and fatigue on cognitive task performance.13 Another study found that tyrosine supplementation may sustain working memory when competing requirements to perform other tasks simultaneously degrade performance, and that supplemental tyrosine may be appropriate for maintaining performance when mild to severe decrements are anticipated.14,15
13. Deijen JB, Wientjes CJ, Vullinghs HF et al. Tyrosine improves cognitive performance and reduces blood pressure in cadets after one week of a combat training course. Brain Res Bull 1999 Jan 15;48(2):203-9.
14. Thomas JR, Lockwood PA, Singh A, et al. Tyrosine improves working memory in a multitasking environment. Pharmacol Biochem Behav 1999 Nov;64(3):495-500.
15. Shukitt-Hale B, Stillman MJ, Lieberman HR. Tyrosine administration prevents hypoxia-induced decrements in learning and memory. Physiol Behav 1996 Apr-May;59(4-5):867-71.
16. Lehnert H, Wurtman RJ. Amino acid control of neurotransmitter synthesis and release: physiological and clinical implications. Psychotherapy and Psychosomatics 1993, 60:18-32.