L-tyrosine, also known simply as tyrosine, is an amino acid — one of 20 organic compounds that combine to form proteins, says the U.S. National Library of Medicine (NLM). If you're considering supplementing with it, you'll want to ensure you're taking the proper l-tyrosine dosage for your needs.
L-tyrosine readily passes the blood-brain barrier, according to the NLM. Once it's in the brain, l-tyrosine serves as a precursor for the neurotransmitters dopamine, norepinephrine and epinephrine, aka adrenalin, says the NLM. These neurotransmitters play key roles in the body's sympathetic nervous system.
L-tyrosine functions in other important ways too. It contributes to hormone production, thyroid function and formation of the human pigment melanin, says the NLM. Finding ways to add it to your diet, whether through food or supplements, can help to ensure you have enough of this amino acid present to do its various jobs throughout the body.
There's also some evidence showing benefits of taking l-tyrosine supplements for certain conditions. Before you start supplementing, however, check with your doctor to discuss the correct tyrosine dosage for depression, l-tyrosine dosage for ADHD or any other health concern.
Daily L-Tyrosine Dosage
Tyrosine is synthesized from the amino acid phenylalanine, says the USDA. Eating foods that are high in phenylalanine — such as beef, chicken, pork, tofu, fish, beans, milk, nuts, seeds, pasta, whole grains and vegetables like sweet potatoes — contributes to adequate production of tyrosine.
To calculate your proper l-tyrosine dosage, you need to consider your phenylalanine intake too. The recommended daily intake (RDI) of phenylalanine and tyrosine is 11 milligrams total per pound of body weight, according to the USDA.
If you get half your daily dosage from each of these amino acids, you should consume 5.5 milligrams of each per pound of body weight, adds the USDA. If you consume only phenylalanine, you should double the RDI.
A Word About Phenylalanine
In some cases, eating too many foods containing phenylalanine can have negative health consequences. For example, people living with phenylketonuria, aka PKU, must limit their intake of phenylalanine.
This rare genetic disorder — caused by a defect in the gene that helps create the enzyme needed to break down phenylalanine — leads to a buildup of phenylalanine in the body, explains the Mayo Clinic. People with PKU may need to take tyrosine supplements because they do not consume phenylalanine, says the USDA.
Phenylalanine is also used as an ingredient in artificial sweeteners containing aspartame, adds the USDA. When consumed in high amounts, aspartame may be problematic — especially for those with PKU who may experience a buildup due to their inability to process phenylalanine.
For example, a June 2014 study in Research in Nursing & Health found that participants, when eating a high-aspartame diet, had more irritable moods, exhibited more depression and performed worse on spatial orientation tests.
Role of L-Tyrosine
Together, dopamine, adrenaline and norepinephrine are part of the catecholamine family, says the Hormone Health Network. These neurotransmitters facilitate important functions related to mood, movement and stress:
- Dopamine: Essential to movement, dopamine influences mood and motivation and contributes to a person's perception of reality, says Harvard Health Publishing. Improper dopamine transmission may lead to psychosis. Because it influences the brain's reward system, it may also play a role in substance abuse.
- Adrenaline: Adrenaline plays a role in the body's fight-or-flight response. When a stressful situation arises, adrenaline causes air passages to dilate and provides muscles with oxygen needed to either fight a perceived danger or flee, says the Hormone Health Network. It also causes an increase in strength and performance and heightened awareness.
- Norepinephrine: Along with adrenaline, norepinephrine increases the heart rate and blood pumping from the heart, says the Hormone Health Network. It increases blood pressure, helps break down fat and increases blood sugar to provide energy to the body.
Note that although adrenaline is a crucial part of the body's stress-response system, overexposure can be damaging to health, adds the Hormone Health Network. When your body regularly releases adrenaline in stressful circumstances, it may create feelings of dizziness, lightheadedness or vision changes.
Adrenaline triggers the release of glucose, adds the Hormone Health Network. If you're a real fight-or-flight situation, your body can put that adrenaline to use as energy. However, in the absence of real danger, you'll have no use for that extra energy — potentially causing heart damage, insomnia or nervous feelings.
L-Tyrosine for Specific Conditions
Because of l-tyrosine's role in mood and stress response, it has been suggested for use with various conditions in which mental function is impaired, explains Winchester Hospital. For example, it's been researched as a treatment for fatigue, depression, attention deficit hyperactivity disorder (ADHD) and other conditions.
There's some evidence that supplementing with l-tyrosine may be beneficial when you're under duress. It may reverse cognitive decline in periods of high cognitive demand or stress, according to a November 2015 study in the Journal of Psychiatric Research. Additional possibilities may include:
- L-tyrosine dosage for ADHD: According to February 2016 research published in Neural Plasticity, amino acids like l-tyrosine have the potential to be used in ADHD treatments due to their effects on the levels of certain neurotransmitters.
- Tyrosine dosage for depression: According to the NLM, more tyrosine is needed under stress. A tyrosine dosage for depression may aid in the stress-induced depletion of norepinephrine. Tyrosine may not advised for people with psychosis, however.
- Tyrosine for Parkinson's disease: L-dopa, used to treat Parkinson's disease, is made from tyrosine, says the NLM.
- Tyrosine for fatigue: An increase in dopaminergic and noradrenergic activity in the brain may contribute to decreased fatigue and feelings of motivation, arousal and reward, according to the Sports Science Exchange.
L-tyrosine does not unequivocally stimulate weight loss, despite claims that it may help speed the metabolism, according to Kaiser Permanente (KP).
In addition, reports vary widely on the effectiveness of l-tyrosine supplementation, says the Journal of Psychiatric Research. More research is needed to determine the link, if any, between l-tyrosine supplements and improved physical performance and their effectiveness in treating clinical disorders.
Amino Acid Supplement Side Effects
Although tyrosine is "generally recognized as safe" by the FDA, it may cause side effects under certain circumstances.
The University of Rochester Medical Center (URMC) warns that using a single amino acid supplement may lead to negative nitrogen balance. This imbalance can negatively impact your metabolism and force your kidneys to work harder. Single amino acid supplements may cause growth problems for children.
URMC also recommends avoiding high doses of a single amino acid for long periods of time. Don't take l-tyrosine if you have melanoma, tyrosinemia type I or II, if you take a monoamine oxidase inhibitor to treat depression, or if you are pregnant or breastfeeding.
In addition, if you have an overactive thyroid (hyperthyroid), check with your health care provider before taking l-tyrosine supplements, says URMC.
Avoid taking l-tyrosine in the evening, as it may be stimulating, adds KP. Long-term use of l-tyrosine should be monitored by a doctor.
Best taken without food, l-tyrosine requires vitamin B6, folic acid and copper for conversion into neurotransmitters, according to KP.
Whether you wish to take l-tyrosine supplements for general health or for a specific condition, talk with your health care provider first. Your doctor can advise you on potential interactions with any medications you may be taking. You'll also want to be sure you're taking the correct l-tyrosine dosage for ADHD, depression or any other condition.
Read more: Side Effects of Too Many Amino Acids
- U.S. National Library of Medicine: "Tyrosine"
- U.S. National Library of Medicine: "Amino Acids"
- USDA: "Top 10 Foods Highest in Phenylalanine"
- Mayo Clinic: "Phenylketonuria (PKU)"
- Research in Nursing & Health: "Neurobehavioral Effects of Aspartame Consumption"
- Harvard Health Publishing: "What Causes Depression?"
- Hormone Health Network: "Norepinephrine"
- Hormone Health Network: "Adrenaline"
- Winchester Hospital: "Health Library: Tyrosine"
- Neural Plasticity: "Natural Product-Derived Treatments for Attention-Deficit/Hyperactivity Disorder: Safety, Efficacy, and Therapeutic Potential of Combination Therapy"
- USDA: "Top 10 Foods Highest in Tyrosine"
- University of Rochester Medical Center: "Tyrosine"
- Sports Science Exchange: "Tyrosine Supplementation: Can This Amino Acid Boost Brain Dopamine and Improve Physical and Mental Performance?"
- Journal of Psychiatric Research: "Effect of Tyrosine Supplementation on Clinical and Healthy Populations Under Stress or Cognitive Demands—A Review"
- Kaiser Permanente: "L-Tyrosine for Weight Control"
- Food and Drug Administration: "CFR - Code of Federal Regulations Title 21"