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TIROSINA

Also known as: Tyrosine, L-Tyrosine, 4-hydroxyphenylalanine

Overview

L-Tyrosine is a non-essential amino acid that serves as a precursor to several important neurotransmitters, including dopamine, norepinephrine, and epinephrine. It is naturally found in protein-rich foods like meat, dairy, and legumes, and can also be synthesized in the body from phenylalanine. Tyrosine supplementation is primarily used to enhance cognitive function under stress, support neurotransmitter synthesis, and potentially improve physical endurance, although evidence for the latter is inconsistent. It plays a crucial role in cognitive alertness, mood regulation, and the body's stress response. Research on tyrosine is moderately mature, with numerous randomized controlled trials and systematic reviews focusing on its cognitive effects. While generally considered safe, it's important to be aware of potential interactions with certain medications and contraindications for individuals with specific thyroid conditions.

Benefits

Tyrosine supplementation has demonstrated cognitive performance enhancement under acute stress by mitigating neurotransmitter depletion. Studies show improvements in cognitive function during short-term stressful or cognitively demanding situations. However, a recent systematic review and meta-analysis found no significant effect of tyrosine supplementation on endurance performance metrics in physically active populations. Tyrosine may also have potential mood stabilization and stress mitigation effects due to its role as a catecholamine precursor, although the evidence is less consistent. Benefits appear most pronounced in individuals undergoing acute cognitive stress rather than in healthy individuals at rest or during physical endurance activities. Cognitive benefits are moderate and context-dependent, while physical performance effects are negligible based on current meta-analytic data.

How it works

Tyrosine functions primarily by serving as a precursor in the synthesis of catecholamine neurotransmitters. It is converted enzymatically into L-DOPA, which is then converted into dopamine, norepinephrine, and epinephrine. These neurotransmitters are crucial for regulating alertness, mood, and the body's response to stress. Tyrosine acts primarily on the central nervous system by replenishing catecholamine stores that are depleted during periods of stress or high cognitive demand. The rate-limiting enzyme in this process is tyrosine hydroxylase. Tyrosine is absorbed in the small intestine and crosses the blood-brain barrier via active transport, competing with other large neutral amino acids.

Side effects

Tyrosine is generally regarded as safe when used at typical supplemental doses. Common side effects are rare, with mild gastrointestinal discomfort occasionally reported. Uncommon side effects, occurring in 1-5% of individuals, may include headache and fatigue. Serious adverse events are rare in controlled trials. Potential drug interactions exist with monoamine oxidase inhibitors (MAOIs) and thyroid medications, so caution is advised. Individuals with hyperthyroidism or Graves' disease should avoid tyrosine supplementation. Limited data are available regarding use in pregnant or breastfeeding women, so caution is advised in these populations. It is important to adhere to recommended dosages to minimize the risk of side effects.

Dosage

The minimum effective dose for cognitive benefits is around 100-150 mg/kg body weight (~7-12 g for a 70 kg adult) in some studies, but lower doses (500 mg to 2 g) are commonly used in supplements. A typical dosage range for cognitive enhancement is 500 mg to 2 g per day, with higher doses used acutely in research settings. The maximum safe dose reported is up to 12 g/day, but long-term safety at high doses is not well established. Acute dosing 30-60 minutes before cognitive or physical stress may be most effective. L-Tyrosine is the preferred form for supplementation. It is best taken on an empty stomach to reduce competition with other amino acids. While no specific cofactors are required, adequate vitamin B6 supports amino acid metabolism.

FAQs

Does tyrosine improve physical endurance?

Current high-quality evidence indicates no significant benefit of tyrosine supplementation on endurance performance in physically active individuals.

Is tyrosine safe for daily use?

Yes, at recommended doses it is generally safe with minimal side effects.

When should I take tyrosine for cognitive benefits?

Ideally 30-60 minutes before anticipated cognitive stress or demanding mental tasks.

Will tyrosine help with mood or depression?

Evidence is limited; benefits may occur only if there is neurotransmitter depletion.

Can tyrosine replace other treatments for stress or cognitive decline?

No, it should not replace medical treatments; it may be an adjunct in specific acute stress situations.

Research Sources

https://pubmed.ncbi.nlm.nih.gov/38290812/ – This study investigated the effects of tyrosine supplementation on cognitive performance. The results suggest that tyrosine may enhance cognitive function under stressful conditions by supporting neurotransmitter synthesis. The study highlights the potential of tyrosine as a cognitive enhancer in specific contexts.
https://www.tandfonline.com/doi/full/10.1080/02640414.2024.2309434 – This systematic review and meta-analysis of 8 RCTs (10 interventions) with physically active adults found no significant effect of tyrosine on endurance performance (time to exhaustion or time trial). The evidence was of moderate quality, and the study highlights the need for further research to clarify the effects of tyrosine on physical performance.
https://pubmed.ncbi.nlm.nih.gov/26424423/ – This review of cognitive and behavioral studies found that tyrosine enhances cognitive performance under acute stress by replenishing catecholamines. The review also noted minimal effects on physical exercise, suggesting that tyrosine's benefits are primarily cognitive rather than physical.
https://academic.oup.com/milmed/article/180/7/754/4160625 – This rapid evidence assessment, including 10 RCTs and 4 controlled clinical trials, found insufficient evidence to recommend tyrosine for physical performance under stress. The assessment provided a weak recommendation for cognitive performance improvement under stress, highlighting the need for further research.
https://www.ahajournals.org/doi/10.1161/HYPERTENSIONAHA.117.10182 – This article focuses on hypertension and its relationship with catecholamines. While not directly about tyrosine supplementation, it provides context on the role of catecholamines in the body and how they can affect blood pressure. This is relevant because tyrosine is a precursor to catecholamines.