L-tyrosine

L-tyrosineTyrosine is a non-essential amino acid. It is made from another amino acid called phenylalanine. The body requires tyrosine for many functions. In particular, this amino acid is closely linked to nervous system function, metabolism and regulating mood.

Tyrosine is necessary to produce the brain chemicals that assist with regulating pain sensitivity and appetite. Also, this amino acid helps the body to respond appropriately to stress. Tyrosine is also required for healthy thyroid, adrenal, and pituitary gland function.

L-tyrosine and mental health

The way we perceive and interact with our environment is governed principally neurotransmitters. Three key neurotransmitters are norepinephrine, dopamine, and epinephrine. To produce these important chemical messengers the body needs phenylalanine and tyrosine. A deficiency in either of these amino acids can lead to mental disorders such as depression and anxiety.

L-tyrosine and stress

There has been a number of studies conducted looking at how l-tyrosine could help to reduce stress. Animal studies confirm that stress induces a lower concentration of important neurotransmitters. However, when administer tyrosine supplements healthy neurotransmitter activity is restored and performance enhanced1.

Human based studies have also found positive correlations between tyrosine supplementation and mental performance. Cadets undertaking a intensive combat training course under stressful situations preformed better after consuming a protein drink containing 10 grams of tyrosine2. The cadets had better memory recall and their blood pressure was normal. This study suggests that l-tyrosine can help to reduce the effects of fatigue and stress on cognitive function.

Another study found that the one-time administration of 150 mg of tyrosine per 2.2 pounds of body weight in a double-blind trial in humans helped to prevent a decline in mental performance for approximately three hours during a night of sleep deprivation3.

Similar findings have been reported in other studies. Once-off administrations of tyrosine (100 to 150 mg per 2.2 pounds of body weight) have also assisted to sustain mental performance during other physically stressful conditions such as extreme cold or excessive noise exposure in several controlled studies4, 5, 6, 7.

L-tyrosine and depression

l-tyrosine Due to the important role tyrosine has in producing neurotransmitters there has been several studies looking at the relationship between this amino acid and depression. It has been established that women taking oral contraceptives tend to have lower tyrosine concentrations and this may trigger depression8, 9.

It’s possible that the metabolism of tyrosine is abnormal in people suffering from depression. There is some research to suggest that tyrosine supplementation may help elevate people out of a depressed state10, 11.

The best results have been achieved when taken together with 5-HTP (5-hydroxy-tryptophan) supplements. 5-HTP is a phytochemical similar to that amino acid tryptophan. It helps to elevate serotonin levels in the brain to improve mood.

Symptoms of a l-tyrosine deficiency

Low energy levels and an erratic mood may be linked to a deficiency in l-tyrosine. Often the symptoms of low tyrosine are similar to that of hypothyroidism. People may experience flu-like symptoms, unexplained weight gain, poor temperature regulation, low blood pressure, sluggish metabolism, depression, dry skin, constipation and brittle hair or fingernails.

Generally low tyrosine levels are uncommon. People who eat a low-protein diet may be susceptible to abnormally low levels of this amino acid. Individuals with the condition phenylketonuria (PKU) are unable to convert phenylalanine into tyrosine. In this case tyrosine becomes an essential amino acid and it must be obtained through supplements.

Dietary sources of l-tyrosine

High protein foods are a good source of this amino acid. This includes turkey, fish, chicken, avocados, almonds, cheese, milk, bananas, yogurt and soy products.

Tyrosine is also available in capsules and powder supplements. Individuals that take tyrosine supplements are recommended to consume them at bedtime. This helps to improve absorption.

It’s important to always consult a doctor before starting tyrosine supplementation. People with high blood pressure or regularly suffering from migraines are advised to not to take tyrosine supplements.

Anyone prescribed monoamine oxidase (MAO) inhibitors are also advised not to take phenylalanine or tyrosine supplements or consume foods rich in these amino acids. This is because in this case both tyrosine and phenylalanine can cause dangerous blood pressure spikes.

Summary

L-tyrosine is very important for nervous system function. We need this amino acid to manufacture key neurotransmitters that help to regulate mood and emotional stability. People experiencing high levels of stress, depression or other mental health instability may need to boost their intake of this amino acid. However, it’s essential that medical advice is sought before using tyrosine supplements to rule out any potential adverse reactions.

References

  1. “Owasoyo J et al. (1992). Tyrosine and its potential use as a countermeasure to performance decrement in military sustained operations. Aviation, Space, and Environmental Medicine, Volume 63, Issue 5, (pp. 364-9.).”
  2. “Deijen J et al. (1999) Tyrosine improves cognitive performance and reduces blood pressure in cadets after one week of a combat training course. Brain Research Bulletin. Volume 48, Issue 2, (pp.203-9).”
  3. “Neri D, et al. (1995).The effects of tyrosine on cognitive performance during extended wakefulness. Aviation, Space, and Environmental Medicine. Volume 66, Issue 4, (pp.313-9).”
  4. “Banderet L and Lieberman H. (1989). Treatment with tyrosine, a neurotransmitter precursor, reduces environmental stress in humans. Brain Research Bulletin. Volume 22, Issue 4, (pp.759-62.)”
  5. “Shurtleff D et al. (1994). Tyrosine reverses a cold-induced working memory deficit in humans. Pharmacology, Biochemistry and Behavior. Volume 47, Issue 4, (pp. 935-41.”
  6. Deijen J and Orlebeke J. (1994). Effect of tyrosine on cognitive function and blood pressure under stress. Brain Research Bulletin. Volume 33, Issue 3, (pp. 319-23).”
  7. Dollins A et al. (1995). L-tyrosine ameliorates some effects of lower body negative pressure stress. Physiology and Behavior. Volume 57, Issue 2, (pp.223-30).”
  8. Rose D and Cramp D. 1970. Reduction of plasma tyrosine by oral contraceptives and oestrogens: a possible consequence of tyrosine aminotransferase induction. Clinica Chimica Acta Volume 29, Issue 1, (pp. 49-53).”
  9. “Moller S. (1981). Effect of oral contraceptives on tryptophan and tyrosine availability: evidence for a possible contribution to mental depression. Neuropsychobiology. Volume 7, Issue 4, (pp. 192-200).”
  10. “Kishimoto H, and Hama Y. (1976). The level and diurnal rhythm of plasma tryptophan and tyrosine in manic-depressive patients. Yokohama Medical Bulletin, Volume 27, (pp. 89-97).”
  11. Gelenberg A and Gibson C (1984). Tyrosine for the treatment of depression. Nutrition and Health. Volume 3, Issue 3, (pp. 163-73).”