What are the uses and benefits of tyrosine supplementation?

Tyrosine Studies and Clinical Uses

Primary Clinical Applications

Tyrosine supplementation has established clinical utility primarily in two contexts: (1) as an essential component of parenteral nutrition for infants and children, and (2) for dietary management of hereditary tyrosinemia type I, where it must be restricted rather than supplemented. 1

Parenteral Nutrition Requirements

Tyrosine is conditionally essential in specific populations and must be provided in amino acid solutions:

• Preterm infants require a minimum of 18 mg/kg/day of tyrosine when receiving parenteral nutrition 1
• Term infants should receive 94 mg/kg/day of tyrosine to maintain normal plasma concentrations 1
• Tyrosine should be included in all amino acid solutions for infants and children, though specific upper limits remain undefined 1, 2

The rationale is that tyrosine becomes essential when phenylalanine hydroxylase activity is insufficient or when dietary protein is severely restricted, as tyrosine cannot be adequately synthesized from phenylalanine under these conditions 1.

Hereditary Tyrosinemia Type I Management

In this metabolic disorder, tyrosine must be restricted, not supplemented:

• Target plasma tyrosine concentration: 200-600 μmol/L (normal range: 35-90 μmol/L) 1
• Dietary intake should be limited to 95-275 mg/day in infants alongside phenylalanine restriction 1
• Both phenylalanine and tyrosine must be restricted because approximately 75% of dietary phenylalanine converts to tyrosine 1
• Specialized medical foods devoid of phenylalanine and tyrosine are required, with age-appropriate vitamin and mineral supplementation 1

Common pitfall: Elevated tyrosine levels in tyrosinemia type I patients treated with NTBC can cause keratitis and other ophthalmologic complications, necessitating careful dietary restriction 1.

Cognitive Performance Enhancement

The evidence for tyrosine supplementation to enhance cognitive performance in healthy adults shows limited and inconsistent benefits:

Stress-Related Cognitive Function

• Tyrosine may provide weak benefit for cognitive performance specifically during acute stress or cognitively demanding situations 3, 4
• The mechanism involves tyrosine serving as a precursor for dopamine and norepinephrine synthesis, which may become temporarily depleted during stress 4, 5
• Typical research dosing: 100-150 mg/kg body weight 3, 5, 6

Evidence Quality and Limitations

The overall evidence quality is insufficient to make confident recommendations for routine use 3:

• A 2015 systematic review found that while all studies examining cognitive stress showed positive effects, the evidence was only sufficient for a "weak recommendation in favor" 3
• Benefits appear limited to situations where neurotransmitter function is intact but temporarily depleted 4
• No benefits have been demonstrated for physical performance enhancement during exercise, including in hot conditions 3, 6

Critical limitation: A 2025 study found tyrosine supplementation (150 mg/kg) completely ineffective for soccer players' physical performance, decision-making, cognitive appraisal, or affective states during high-intensity intermittent exercise in 32°C heat 6.

Phenylketonuria (PKU) Management

Tyrosine supplementation for PKU shows no clear clinical benefit beyond what is provided in standard medical foods:

• A Cochrane systematic review (2021) concluded that no recommendations can be made about introducing tyrosine supplementation into routine clinical practice for PKU 7
• While tyrosine supplementation increases blood tyrosine concentrations, no significant differences were found in intelligence, neuropsychological performance, growth, nutritional status, or quality of life 7
• Tyrosine is already included in phenylalanine-free medical foods used for PKU management 1

Important consideration: Tyrosine becomes conditionally essential in PKU because phenylalanine hydroxylase deficiency prevents adequate conversion of phenylalanine to tyrosine 1. However, the tyrosine provided in standard medical foods appears sufficient without additional supplementation 7.

Cardiovascular and Other Clinical Applications

No established cardiovascular benefits exist:

• The ACC/AHA guidelines do not recommend taurine or other nutritional supplements including tyrosine for heart failure treatment 2
• ESPEN does not suggest routine addition of individual amino acids including tyrosine in parenteral formulas for adults on home parenteral nutrition 2

Practical Clinical Algorithm

For determining tyrosine use in clinical practice:

1. If patient is an infant/child on parenteral nutrition → Ensure amino acid solution contains tyrosine at recommended doses (18 mg/kg/day minimum for preterm, 94 mg/kg/day for term infants) 1

2. If patient has hereditary tyrosinemia type I → Restrict tyrosine intake to 95-275 mg/day in infants, target plasma levels 200-600 μmol/L, use specialized medical foods 1

3. If patient has PKU → Use standard phenylalanine-free medical foods containing tyrosine; additional supplementation not recommended 1, 7

4. If considering for cognitive enhancement in healthy adults → Evidence insufficient for routine recommendation; may consider only for acute, short-term stressful situations at 100-150 mg/kg, but benefits are marginal and inconsistent 3, 4

5. If considering for physical performance → Do not use; no demonstrated benefits 3, 6

Key monitoring parameters when tyrosine is used therapeutically: Plasma amino acid concentrations should be checked periodically, with particular attention to maintaining tyrosine within target ranges and preventing deficiencies of phenylalanine or other amino acids 1.