L-tyrosine

A non-essential amino acid you get from protein in the diet and also make yourself from phenylalanine. It is the raw material the body uses to build dopamine, noradrenaline and adrenaline.

Acute stress speeds up the turnover of noradrenaline and dopamine faster than the enzyme tyrosine hydroxylase can replace them, and the supply of tyrosine becomes the limiting step. Extra tyrosine refills that pool, which is why the result reads as performance that does not fall rather than performance that rises. In a rested, unstressed person there is no depletion to relieve, and that is where the trials stop showing anything. The 2015 review of the field reached the same place: the benefit sits in short-term stressful or cognitively demanding conditions and not outside them. That asymmetry is the mechanism, and it is also the honest limit of it.

Supplies the precursor for normal catecholamine synthesis. It has been studied for maintaining cognitive performance during short, acutely stressful conditions such as cold, altitude, noise and sleep loss.

People facing a short bout of genuine stress — a cold session, a night shift, a sleep-deprived early start — who are prepared to dose it separately and properly. Not for anyone on MAOIs or levodopa, not for people with hyperthyroidism, Graves' disease or hereditary tyrosinaemia, and not worth seeking out by anyone who is well rested, because that is exactly the group the evidence says gets nothing.

In the trials it is taken 30 to 60 minutes before the stressful task, on an empty stomach. A protein-heavy meal puts other large neutral amino acids in competition for the same transporters, so food blunts it. Keep it at least two hours away from levodopa. Within IGNITE there is no timing decision to make, because there is no meaningful dose to time.

Nothing you will notice at this amount. Even at a full 8–12 g dose the effect is not a sensation — it is the absence of a decline you would otherwise have had, which is invisible unless somebody is testing you. In a scoop of IGNITE, the lift is the 175 mg of caffeine and the tingle is the beta-alanine. Neither of those is this.

Banderet and Lieberman (1989, Brain Research Bulletin 22:759–762) gave 100 mg/kg in a double-blind crossover before 4.5 hours of combined cold and hypoxia, and reported reduced symptoms, adverse mood and performance impairment in the subjects most affected by those conditions. Deijen et al. (1999, Brain Research Bulletin 48:203–209) ran 21 cadets through a demanding combat training course: ten received a protein-rich drink supplying 2 g of tyrosine per serving, five servings daily, against eleven on a calorie-matched carbohydrate drink, and the tyrosine group performed better on memory and tracking tasks with lower systolic blood pressure. Mahoney et al. (2007, Physiology & Behavior 92:575–582) gave 19 volunteers 150 mg/kg before each of two 90-minute cold-water immersions and found working-memory decrements mitigated. Attipoe et al. (2015, Military Medicine 180:754–765) pooled 10 randomised controlled trials and 4 controlled clinical trials and issued a weak recommendation in favour of tyrosine for cognitive stress — while stating that no recommendation could be made for physical performance. Jongkees et al. (2015, Journal of Psychiatric Research) reviewed the same literature, logged doses from 500 mg to 12 g a day, and concluded the benefit is confined to short-term stressful or cognitively demanding situations. What is not supported: any benefit in rested, unstressed people; any effect on strength, power or endurance; and any effect at all at roughly 78 mg.