Five actives. Every dose. Every study.

An amino acid you already get from protein. Your brain turns it into L-DOPA, then dopamine, then norepinephrine. Under sustained demand those stores run down faster than the diet tops them up. Vitamin B6, in its active form, is the cofactor for the enzyme that makes the final step from L-DOPA to dopamine. Tyrosine gives the pathway raw material; B6 lets the last step happen.

A 2015 review of the human studies concluded tyrosine enhances cognition mainly in short-term stressful or demanding situations, when dopamine or norepinephrine is temporarily depleted, and that reports vary, with some studies finding benefits and others not. Jongkees 2015 In a working-memory task, tyrosine improved the harder 2-back condition but not the easier 1-back. Colzato 2013 Under 4.5 hours of cold and low oxygen, 100 mg/kg reduced symptoms, adverse moods and performance impairments in the people who reacted most to the stress. Banderet 1989 In 21 cadets on a week of combat training, a 2 g daily tyrosine drink beat a carbohydrate drink on memory and tracking tasks; mood was unchanged. Deijen 1999

Plain L-tyrosine, the form used in the studies. 750 mg is what fits in a stick you can drink twice a day. It is below the doses in most of the positive studies, which used 2 g or more, sometimes far more. We'd rather say that than round up.

The strongest results come from stress, sleep loss and cold, not from an ordinary desk day. Effects on mood were not found in the cadet study, and the review is explicit that tyrosine helps only when neurotransmitter function is intact and temporarily depleted.

• Jongkees BJ et al. Effect of tyrosine supplementation on clinical and healthy populations under stress or cognitive demands. J Psychiatr Res 2015;70:50-7.
• Colzato LS et al. Working memory reloaded: tyrosine repletes updating in the N-back task. Front Behav Neurosci 2013;7:200.
• Banderet LE, Lieberman HR. Treatment with tyrosine, a neurotransmitter precursor, reduces environmental stress in humans. Brain Res Bull 1989;22(4):759-62.
• Deijen JB et al. Tyrosine improves cognitive performance and reduces blood pressure in cadets after one week of a combat training course. Brain Res Bull 1999;48(2):203-9.

L-alpha-glycerylphosphorylcholine, a form of choline that crosses into the brain, where choline is the building block of acetylcholine. Tyrosine and B6 work on dopamine and norepinephrine; Alpha-GPC works on a different messenger, acetylcholine. Different pathway, same job: holding attention on the thing in front of you.

Most of the evidence is in people with memory problems, not healthy adults. In a 12-week trial of 100 older adults with mild cognitive impairment, 600 mg a day improved the ADAS-cog score more than placebo, with adverse-event rates similar to placebo. Jeon 2024 In healthy adults the evidence is new and thin. In 20 resistance-trained men, a single 315 mg or 630 mg dose improved Stroop scores an hour later versus placebo, while N-back and Flanker tasks did not change. Kerksick 2024 An earlier crossover in 20 young adults found no statistically significant effect of 200 or 400 mg on mood, cognition or performance 30 minutes after the dose. Parker 2015

300 mg of Alpha-GPC, supplied as 600 mg of a 50% standardised extract. That sits between the 200–400 mg that showed nothing significant and the 315 mg low dose that did, and at half the daily dose used in the memory-impairment trial.

Very mixed. As of 2020 an independent review found no studies in healthy people at all; the two since are small, single-dose, and one was industry-linked. The 2024 healthy-men study found benefit on one of three tasks. We include Alpha-GPC on mechanism and the memory-impairment data, and we won't pretend the healthy-adult evidence is settled.

• Jeon J et al. Efficacy and safety of choline alphoscerate for amnestic mild cognitive impairment: a randomized double-blind placebo-controlled trial. BMC Geriatr 2024;24:774.
• Kerksick CM. Acute alpha-glycerylphosphorylcholine supplementation enhances cognitive performance in healthy men. Nutrients 2024;16(23):4240.
• Parker AG et al. The effects of alpha-glycerylphosphorylcholine, caffeine or placebo on markers of mood, cognitive function, power, speed, and agility. J Int Soc Sports Nutr 2015;12(Suppl 1):P41. Conference abstract.
• Alzheimer's Drug Discovery Foundation, Cognitive Vitality: Alpha-GPC. Updated March 2020.

The amino acid that makes tea feel different from coffee. It is almost always studied alongside caffeine, because that's how people meet it. It's here for the caffeine. The combination studies are the reason the stick is caffeine plus theanine rather than caffeine alone.

With caffeine, the results are consistent across several trials. 250 mg theanine with 150 mg caffeine improved reaction time, working-memory speed, sentence-verification accuracy and alertness versus placebo, where neither alone did as much. Haskell 2008 100 mg with 50 mg caffeine improved both speed and accuracy of attention switching at 60 minutes in 27 volunteers. Owen 2008 97 mg with 40 mg caffeine improved task-switching accuracy and alertness and reduced tiredness in 44 young adults. Giesbrecht 2010 A meta-analysis of 11 placebo-controlled studies found moderate effects of the combination on alertness and attention-switching accuracy in the first two hours. Camfield 2014 On its own, 200 mg a day for four weeks lowered stress, anxiety and sleep-problem scores and improved verbal fluency in 30 healthy adults. Hidese 2019

200 mg is the daily dose from the four-week trial and sits inside the 97–250 mg range of the combination studies. The two-to-one ratio with caffeine matches the 100 mg : 50 mg pairing that improved attention switching.

Alone, theanine did not help in the acute study, and even raised headache ratings. Haskell 2008 The meta-analysis notes the effect tracks the caffeine dose more than the theanine dose. Two of the combination trials came from a tea company's research arm, and the four-week trial was supplied by the ingredient's maker.

• Haskell CF et al. The effects of L-theanine, caffeine and their combination on cognition and mood. Biol Psychol 2008;77(2):113-22.
• Owen GN et al. The combined effects of L-theanine and caffeine on cognitive performance and mood. Nutr Neurosci 2008;11(4):193-8.
• Giesbrecht T et al. The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness. Nutr Neurosci 2010;13(6):283-90.
• Camfield DA et al. Acute effects of tea constituents L-theanine, caffeine, and epigallocatechin gallate on cognitive function and mood: a systematic review and meta-analysis. Nutr Rev 2014;72(8):507-22.
• Hidese S et al. Effects of L-theanine administration on stress-related symptoms and cognitive functions in healthy adults: a randomized controlled trial. Nutrients 2019;11(10):2362.

Caffeine, extracted from green tea leaf. Chemically it is the same molecule as the caffeine in coffee; "natural" tells you where it came from, not that it works differently. Theanine is paired with it because the combination outperformed caffeine alone in the trials above. Caffeine handles alertness; the other four handle attention.

A 2016 review: caffeine blocks adenosine receptors, and at low to moderate doses, about 40 mg to 300 mg, alertness, vigilance, attention and reaction time improve. Effects on memory and higher-order judgement are less consistent. McLellan 2016 On safety, the European Food Safety Authority concluded single doses up to 200 mg and daily intakes up to 400 mg raise no safety concerns for healthy adults, that 200 mg a day is the ceiling in pregnancy, and that 100 mg can affect sleep in some adults when taken close to bedtime. EFSA 2015

100 mg is about a cup of coffee, inside the range where the review sees the clearest attention effects, and low enough that two sticks stay under 400 mg with room for a coffee. Green tea leaf extract, because that's where the theanine comes from too.

Nothing mixed about the alertness effect. What caffeine doesn't reliably do is improve memory or judgement. And taken late, 100 mg is enough to shorten some people's sleep, which is why we say two a day and not near bedtime.

• McLellan TM, Caldwell JA, Lieberman HR. A review of caffeine's effects on cognitive, physical and occupational performance. Neurosci Biobehav Rev 2016;71:294-312.
• EFSA Panel on Dietetic Products, Nutrition and Allergies. Scientific Opinion on the safety of caffeine. EFSA Journal 2015;13(5):4102.

Pyridoxal 5'-phosphate, the coenzyme form of vitamin B6. Most supplements use pyridoxine hydrochloride, which the body has to convert; P5P is the form the enzymes actually use. NIH ODS It's here for the tyrosine. Tyrosine becomes L-DOPA; the P5P-dependent enzyme turns L-DOPA into dopamine.

P5P is the essential cofactor for aromatic L-amino acid decarboxylase, the enzyme that carries out the final step in making dopamine and serotonin; when P5P is short, the enzyme's activity and protein levels fall. Allen 2010 The adult RDA is 1.3 mg and the tolerable upper intake level is 100 mg a day. NIH ODS

10 mg is 588% of the Daily Value and a tenth of the upper limit, enough to make sure the cofactor isn't the bottleneck, without getting anywhere near the doses linked to nerve problems with long-term use.

There's no study showing extra B6 sharpens focus in people who already get enough. The case for it is biochemical: the pathway needs it, so it's in the stick. The cell study above also found that adding more P5P outside the cell didn't raise the enzyme's activity further.

• Allen GF et al. Pyridoxal 5'-phosphate deficiency causes a loss of aromatic L-amino acid decarboxylase in patients and human neuroblastoma cells. J Neurochem 2010;114(1):87-96.
• National Institutes of Health, Office of Dietary Supplements. Vitamin B6: Fact Sheet for Health Professionals.