Tyrosine as a therapeutic supplement
Tyrosine is a naturally occurring amino acid that plays a crucial role in the body, particularly in the synthesis of neurotransmitters essential for brain and nervous system function. It has been explored as a potential therapeutic supplement for various conditions, including attention deficit hyperactivity disorder (ADHD), depression, fatigue, and recovery from jet lag. While the body can produce tyrosine from another amino acid, phenylalanine, deficiencies may occur in specific metabolic disorders like phenylketonuria (PKU) or severe kidney diseases. Common dietary sources of tyrosine include dairy products, nuts, meats, and beans.
Research suggests that tyrosine supplements may help improve mental alertness during periods of sleep deprivation and may offer temporary benefits for ADHD, although the effects may diminish over time. Preliminary studies indicate potential cognitive benefits under stress, but evidence supporting its use for depression remains inconclusive. Tyrosine is generally considered safe for most individuals, although high doses may lead to side effects like nausea or vomiting. Caution is advised for certain populations, including those with hyperthyroidism or individuals on specific medications. Overall, while there is interest in tyrosine as a supplement, further research is needed to establish its efficacy across various conditions.
Tyrosine as a therapeutic supplement
DEFINITION: Natural substance of the human body used as a supplement to treat specific health conditions.
PRINCIPAL PROPOSED USES: None
OTHER PROPOSED USES: Attention deficit hyperactivity disorder, depression, enhancing mental function, fatigue, jet lag, enhancing sports performance
Overview
Tyrosine is an amino acid found in meat proteins. The body uses it as a starting material to make several neurotransmitters—chemicals that help the brain and nervous system function. Tyrosine has been proposed as a treatment for various conditions in which mental function is impaired or slowed down, such as fatigue and depression. It also has been tried for attention deficit hyperactivity disorder (ADHD).
Requirements and Sources
The body makes tyrosine from another common amino acid, phenylalanine, so deficiencies are rare. However, they can occur in certain forms of severe kidney disease as well as in phenylketonuria (PKU), a metabolic disorder that requires complete avoidance of phenylalanine. Good sources of tyrosine include dairy products, sesame seeds, nuts, meats, fish, and beans.
Therapeutic Dosages
The typical therapeutic dosage of tyrosine used in many studies ranges from 7 to 30 grams daily. However, some research suggests using between 100 and 300 milligrams per kilogram of body weight each day. These supplements should be taken at least thirty minutes before eating. Some individuals take copper, folate, or vitamin B6 supplements with tyrosine to help the body process the supplement.
Therapeutic Uses
Tyrosine supplements are most often used by individuals with the inherited disorder phenylketonuria (PKU) to aid in producing the amino acid phenylalanine. These individuals may receive tyrosine through foods or supplements, though supplements do not have sufficient evidence to support their efficacy. Preliminary evidence, including small double-blind trials, suggests that tyrosine supplements may help fight fatigue and improve memory and mental function in people deprived of sleep or exposed to other forms of stress. Based on these findings, it has been inferred that tyrosine might enhance alertness in people suffering from jet lag, but this has not been studied directly.
Tyrosine may also provide some temporary benefits for attention deficit hyperactivity disorder (ADHD), but the benefits appear to wear off in about two weeks. Tyrosine is said to work better for this purpose when combined in an “amino acid cocktail” along with gamma-aminobutyric acid (GABA), phenylalanine, and glutamine; however, no scientific evidence supports this use.
Although one extremely tiny study found tyrosine helpful for depression, a larger study found no evidence of benefit. Tyrosine has also been suggested to enhance sports performance. However, in a double-blind study of twenty men, one-time use of tyrosine at a dose of 150 milligrams per kilogram body weight failed to improve any measurement of muscular performance.
Scientific Evidence
Sleep deprivation. A double-blind, placebo-controlled study that enrolled twenty US Marines suggests that tyrosine can improve mental alertness during periods of sleep deprivation. In this study, the participants were deprived of sleep for a night and then tested frequently for their alertness throughout the day as they worked. Compared to placebo, ten to fifteen grams of tyrosine given twice daily seemed to provide a “pick-up” for about two hours. Similar benefits were seen with two grams of tyrosine daily in a double-blind, placebo-controlled trial of twenty-one military cadets exposed to physical and psychological stress.
Depression. Individuals who are diagnosed with depression often have low tyrosine levels, and tyrosine helps with the production of dopamine. This led researchers to posit its ability to treat depression. However, no conclusive research has been found to support this theory. A pilot study that enrolled nine individuals is widely quoted as proving that tyrosine can help depression. However, this study was too small to provide reliable results. A subsequent double-blind, placebo-controlled study of sixty-five people with depression failed to find any benefit.
Safety Issues
Tyrosine is generally safe, but at high dosages, some people have reported nausea, diarrhea, vomiting, or nervousness. As with any other supplement taken in multigram doses, it is important to use a high-quality product; even a very small percentage of contaminant in the product might add up to a dangerous amount. Maximum safe dosages for young children, women who are pregnant or nursing, and those with severe liver or kidney disease have not been established.
Individuals with hyperthyroidism or Grave’s disease should avoid tyrosine supplements because they may increase thyroid hormone levels. People taking Levodopa for Parkinson's disease or monoamine oxidase inhibitors for depression should also avoid this supplement.
Bibliography
Mahoney, C. R., et al. “Tyrosine Supplementation Mitigates Working Memory Decrements During Cold Exposure.” Physiology and Behavior, vol. 92, no. 4, 2007, pp. 575-82.
Sutton, E. E., et al. Ingestion of Tyrosine: Effects on Endurance, Muscle Strength, and Anaerobic Performance.” International Journal of Sport Nutrition and Exercise Metabolism, vol. 15, 2005, pp. 173-185.
"Tyrosine." Icahn School of Medicine at Mount Sinai, www.mountsinai.org/health-library/supplement/tyrosine. Accessed 20 Sept. 2024.
"Tyrosine - Uses, Side Effects, and More." WebMD, www.webmd.com/vitamins/ai/ingredientmono-1037/tyrosine. Accessed 20 Sept. 2024.