L tyrosine

L-tyrosine is an amino-acid precursor in the dopamine pathway; supplementation may increase alertness, focus, motivation, and cognitive performance, including working memory in multitasking situations. 1 2

• Effects and timing: Effects may start around 30–45 minutes after taking it. For a cognitive task, the cited research used it about an hour beforehand. 3 4
• Dose: Common supplement amounts mentioned are 500–1,000 mg, with 250–500 mg suggested as a cautious starting range; 500–1,500 mg may be used before a task. The 10-gram research dose was explicitly not recommended. 5 6
• Cautions: Some people report an energy or mood crash afterward, and frequent use was discouraged. Caution was advised for people with bipolar disorder, schizophrenia, psychosis, or other dopamine-related conditions. 7 8
• Forms, food, and timing: Supplements are available as capsules or powder; tyrosine also occurs in foods such as meat, nuts, and some plant foods. Huberman advised taking supplemental tyrosine early in the day because it can act as a stimulant. 9 10 11