Tyrosine is a nonessential amino acid that is naturally synthesized in your body but can also be obtained in many high-protein foods such as soy and dairy products, fish, nuts, seeds and avocados. Tyrosine is important for the formation of brain neurotransmitters and hormones, which help regulate everything from metabolism and cardiovascular function to emotions and memory. Tyrosine intolerance occurs when your body acquires too much of this substance, causing an overdose. This can occur when you eat a very high-protein, high-fat diet with very low carbohydrates.
When your body contains too much tyrosine, it may cause adverse effects on your thyroid gland, which produces hormones that regulate your metabolism. Hyperthyroidism is a condition in which your thyroid gland overproduces thyroid hormones, and is sometimes caused by excessive amounts of tyrosine. Symptoms of hyperthyroidism include difficulty concentrating, chronic fatigue, frequent bowel movements, swelling around your neck, heat intolerance, increased appetite, excessive sweating, irregular menstruation in women, nervousness, anxiety and unexplained weight loss.
Allergic reactions to tyrosine are rare because your body can synthesize it naturally, making it a nonessential amino acid. But allergic reactions do occur. An allergic reaction to tyrosine is marked by an increase in the production of histamine, which may cause skin rashes, particularly around your face and neck, as well as itching, swelling, coughing and difficulty breathing. If you experience any of these symptoms, consult your physician to take an allergy test to determine if tyrosine or some other substance is causing your allergies.
Some individuals may have trouble absorbing dietary tyrosine, but may not experience the effects of a tyrosine deficiency because it is naturally occurring in your body. Dietary tyrosine is absorbed by your small intestine, where it is then transferred to your bloodstream and throughout your body so it can exert its effects on various bodily tissues. If your small intestine is not able to absorb dietary tyrosine due to an illness or infection, you may experience nausea, persistent stomach cramps and diarrhea.
Tyrosine and Neurotransmitters
Tyrosine is essential for the normal production of several key neurotransmitters in your brain, particularly dopamine and serotonin. If your body has acquired too much tyrosine, it may initially increase, then substantially decrease, the production of these two compounds. This may lead to changes in your mood such as increases in anxiety and depression and disruption of memory and cognition, as well as physical effects including body tremors, numbness in your hands and feet and muscle spasms. It may even increase your risk of seizures. If you take antidepressants or mood elevators, you may be cautioned not to take excess amounts of tyrosine as it can make your symptoms worse. If you suffer from anxiety or depression, consult your physician to assess whether your tyrosine intake will adversely affect those conditions.
- "Essentials of Sports Nutrition and Supplements"; Jose Antonio, Douglass Kalman, Jeffrey R. Stout, and Mike Greenwood; 2008
- "Nutrition for Health, Fitness, and Sport"; Melvin H. Williams; 2002
- Pub Med Health; Hyperthyroidism; 2010