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Amino AcidClinical dose · 100–150mg/kg in the key stress trials (about 7–10g for a 70kg adult); consumer products give flat 500–2000mg dosesOnset · About 1 hour before a demanding cognitive task

L-Tyrosine (NALT)

Military and stress trials found tyrosine reduced performance decline during one night of sleep loss (Neri et al., 1995, 150mg/kg), noise stress (Deijen & Orlebeke, 1994, 100mg/kg) and a combat training course (Deijen et al., 1999, 2g/day) — but neither Deijen trial found any effect on mood. Other trials were null or negative: tyrosine did not protect cognition or performance under exercise heat stress (Coull 2016, 150mg/kg), and 2g worsened cognitive flexibility under high cognitive load (Robson 2019). A 2015 narrative review (Jongkees et al.) concluded benefits are conditional on short-term stress that depletes dopamine and norepinephrine.

By The Nootropic Lab editorial teamUpdated 8 min read✓ Fact-checked

Evidence reviewed:

Mechanism of action

L-Tyrosine is an amino acid precursor to dopamine, norepinephrine, and epinephrine. Under conditions of stress, sleep deprivation, or cognitive load, the brain depletes catecholamine stores. Supplementing tyrosine replenishes the substrate for neurotransmitter synthesis, maintaining cognitive performance when it would otherwise decline.

Clinical evidence summary

Military and stress trials found tyrosine reduced performance decline during one night of sleep loss (Neri et al., 1995, 150mg/kg), noise stress (Deijen & Orlebeke, 1994, 100mg/kg) and a combat training course (Deijen et al., 1999, 2g/day) — but neither Deijen trial found any effect on mood. Other trials were null or negative: tyrosine did not protect cognition or performance under exercise heat stress (Coull 2016, 150mg/kg), and 2g worsened cognitive flexibility under high cognitive load (Robson 2019). A 2015 narrative review (Jongkees et al.) concluded benefits are conditional on short-term stress that depletes dopamine and norepinephrine.

Human effect matrix

Based on human clinical trials only. Animal and in-vitro data excluded.

EffectEvidenceMagnitudeStudies
Cognitive Performance Under Stress mixed
Moderate
6
Mood Under Stress mixed
Negligible
2

Evidence key: Strong = multiple consistent RCTs · Moderate = smaller/fewer RCTs · Preliminary = early trials or small n · Mixed = conflicting results

Documented benefits

  • Cognitive performance under some acute stressors (sleep loss, noise, combat training)
  • Focus in demanding conditions

Side effects & cautions

  • Generally safe
  • May worsen cognitive flexibility under high cognitive load (one RCT at 2g)
  • MAO inhibitors: theoretical interaction (tyrosine is a catecholamine precursor), no clinical reports found — ask your doctor before combining
  • Possible hyperthyroid effects at very high doses
  • May interact with thyroid medications

How to take

Dosage500–2000mg L-Tyrosine (flat dose). Several classic stress trials used weight-based doses of 100–150mg/kg (7–10g for a 70kg adult), so consumer doses are not equivalent to the doses shown effective in those trials
Timing30–60 minutes before the demanding task, exam, workout, or stressful event. Unlike most nootropics, timing relative to the demand matters significantly for tyrosine.
With foodBest absorbed on an empty stomach or with a low-protein snack. High-protein meals compete for amino acid transporters and reduce tyrosine uptake into the brain significantly. Avoid taking with a protein shake or high-meat meal.
FormsCapsule or powder. L-Tyrosine (the free amino acid form) is best value and is the form used in the stress trials. NALT (N-Acetyl-L-Tyrosine) is common in formulated stacks, but no trial comparing NALT with plain L-Tyrosine for cognition was found.

Stacking recommendations

Ingredients that pair well with L-Tyrosine (NALT) and why.

L-Theanine

L-Tyrosine supplies dopamine/norepinephrine substrate for focus and drive; L-Theanine keeps you calm and prevents the cortisol spike from stress or caffeine. Together they produce focused, calm high-performance state under demanding conditions.

Rhodiola Rosea

Rhodiola modulates monoamine availability and HPA axis; Tyrosine replenishes the substrate for those monoamines. Both work best under stress conditions — they target the same problem (cognitive decline under stress) via complementary mechanisms.

Caffeine

Often paired with caffeine; we cite no trial of L-Tyrosine with caffeine.

Frequently asked questions

Does L-Tyrosine work if I am not stressed or sleep-deprived?

Probably not meaningfully. This is the key nuance of tyrosine. The evidence shows it prevents cognitive decline under stress — it restores depleted catecholamines. In a rested, non-stressed baseline state, catecholamine levels are already sufficient, so adding precursor does not produce a noticeable effect. Think of it as an insurance policy for demanding days, not a daily cognitive enhancer.

L-Tyrosine vs NALT — which form should I buy?

Plain L-Tyrosine. The stress trials with positive results used plain L-Tyrosine — at 2g/day or at weight-based doses of 100–150mg/kg — taken about an hour before the demand. NALT is commonly used in formulated stacks (easier to cap), but no trial comparing it with plain L-Tyrosine for cognition was found.

Does it interact with thyroid medications?

Yes — L-Tyrosine is a precursor to thyroid hormones (T3 and T4). At standard doses, this is not clinically significant for most people. However, if you have hyperthyroidism or are on levothyroxine or other thyroid medications, supplemental tyrosine could theoretically affect hormone levels. Consult your doctor before use if you have any thyroid condition.

Can L-Tyrosine help with ADHD?

It is not established. Tyrosine is a dopamine precursor, but our 2026 evidence review did not assess ADHD trials, and a 2015 review judged its potential for treating clinical disorders minimal. L-Tyrosine is not a substitute for ADHD treatment — talk to your doctor before combining it with any medication.

Top stacks containing L-Tyrosine (NALT)

Mind Lab Pro

7.5/10

Performance Lab

Editor's Choice

NooCube

7/10

Wolfson Brands

L-Tyrosine (NALT) in Japan

Products in Japan

Consumer Affairs Agency (FFC)

Prefecture guides

Regulatory note

本ページは教育目的の編集コンテンツであり、医学的助言を構成するものではありません。日本国内で販売される機能性表示食品（FFC）および特定保健用食品（FOSHU）は、消費者庁への届出または許可を必要とします。届出のない輸入品については、日本の薬機法（旧薬事法）の下で疾病治療を示唆する表現は規制されます。サプリメントを開始する前に、必ず資格のある医療専門家にご相談ください。This page is editorial and not medical advice. Foods with Function Claims (FFC) and Foods for Specified Health Uses (FOSHU) sold in Japan require notification or approval from the Consumer Affairs Agency. Imported products without notification cannot make disease-treatment claims under the Pharmaceuticals and Medical Devices (PMD) Act. Consult a qualified healthcare professional before starting any supplement.

Sources (6)expand
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