Amino Acid
Phenylalanine
An essential amino acid that serves as a precursor to dopamine, norepinephrine, and other neurotransmitters.
KÖGN Health grades Phenylalanine as B+ (Moderate evidence) and rates it 3.9 out of 5.
Last reviewed · June 2026
Primary effects
- Improved mood
- Increased motivation
- Cognitive support
How it works
Supports neurotransmitter synthesis involved in mood, motivation, and cognitive function.
Overview
Phenylalanine is a dietary amino acid that contributes to the production of key neurotransmitters involved in alertness and mood regulation. Its cognitive effects are generally subtle and depend on individual nutritional status and metabolic needs. It is more effective as a foundational nutritional support compound rather than a targeted performance enhancer.
The evidence
Phenylalanine is an essential amino acid and a precursor — via tyrosine — to dopamine and noradrenaline, which is the basis for its use in mood and alertness. Direct, good-quality human trials for cognition are limited; the rationale is mechanistic and overlaps heavily with L-tyrosine, which is the more commonly studied step in that pathway.
How to dose it
Supplement doses vary widely (commonly several hundred milligrams to ~1–2 g/day). The DL- and L- forms differ; effects in healthy, well-fed people are modest.
When to take it
Acute — as a catecholamine precursor, taken ahead of demand.
Safety & side effects
Generally well tolerated in healthy people at sensible doses.
Who should avoid it
Must be strictly avoided by anyone with phenylketonuria (PKU). Take care with MAOIs (risk of raised blood pressure) and discuss with a clinician if you take antipsychotics or are pregnant. See also L-Tyrosine, the next step in the same pathway.
References
Related ingredients
Graded entries that target the same cognitive goals.
Categories
Draft — the dose, safety and evidence notes on this entry were prepared from the published literature and are pending editorial and clinical review.
Educational information, not medical advice. The evidence grade is KÖGN’s editorial assessment of published research, not a health claim. Speak to a qualified clinician before changing what you take.