L-Tyrosine Side Effects, Dangers, and Interactions

L-Tyrosine is a dietary supplement that is used to improve mood, increase energy levels, and enhance mental and physical performance.

Tyrosine capsules are frequently taken as a nootropic to boost concentration and to support weight loss and improve workout intensity among bodybuilders.

The L isomer of tyrosine (4-hydroxyphenylalanine) is one of the amino acids used to make proteins.

It serves various other purposes as well; including regulating thyroid function, reducing the perceptions of stress; and serving as a precursor to catecholamines like Dopamine, Epinephrine (Adrenaline), and Norepinephrine (Noradrenaline).

It is able to be manufactured inside the body via another amino acid, Phenylalanine, by the enzyme phenylalanine hydroxylase. Phenylalanine is present in various food sources and L-Tyrosine itself can be found in foods such as cheese and other protein sources.

Being well tolerated in the body, L-Tyrosine side effects are not common under normal usage. However, some individuals may experience adverse effects that can include headaches, gastrointestinal upset, and temporary mood disturbances.

Tyrosine

Amino Acid

Motivation

Mental Focus

Mood

How It Works:

• Supports energy & motivation
• Promotes focus & mental clarity
• Improves mood & stress response

Dosage:

Between 500 - 2000 mg per day

Safety:

Rated Likely Safe

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L-Tyrosine Effects in the Body

L-Tyrosine is one of twelve non-essential amino acids found in the body.

Because it is non-essential, humans do not need to consume it from foods in order to prevent a deficiency. It can be made from the essential amino acid Phenylalanine within the body.

However, increasing L-Tyrosine levels in the body may have certain health benefits for those with low levels or in specific cases. Many of the purported therapeutic effects of L-Tyrosine have not been clinically substantiated.

However, in research studies, the following has been demonstrated following L-Tyrosine administration:

• Increased plasma levels of Norepinephrine and Dopamine
• Improved the moods of individuals who have been exposed to stress
• Improved cognitive and physical performance in individuals exposed to cold temperatures, sleep deprivation, prolonged work periods and/or fatigue
• Reduced stress hormone levels (particularly cortisol)
• Reduced stress-induced weight gain
• Upregulated thyroxine (T4) thyroid production
• Increased feelings of subjective well-being
• Reduced blood pressure, especially during stressful events

There has been limited research into the benefits and side effects of L-Tyrosine for cognitive or physical functioning under non-stressful conditions. More research is needed to determine efficacy for normal, healthy adults who are not experiencing external stressors.

Mood Benefits of L-Tyrosine

Some individuals supplement with L-Tyrosine to help them better cope with daily stress. Clinical experiments have shown that subjects are able to better handle stressful situations when supplementing with this amino acid.

One study found that cold-induced decreases in cognitive performance were mitigated in patients who took L-Tyrosine before acute cold stress compared to placebo patients. Another similar study found that memory was improved in patients who were given Tyrosine versus placebo patients in a cold stress test.

The anti-anxiety effects of L-Tyrosine are believed to be caused by increasing catecholamine production. Catecholamines are monoamine compounds that act as hormones and neurotransmitters in the body. The main catecholamines are Dopamine, Epinephrine, and Norepinephrine. They have a stimulatory effect on the mind and on the body.

Stress has been seen to deplete catecholamine levels. It has been hypothesized that supplementing with Tyrosine will provide more raw materials to increase catecholamine production, and potentially avoid the negative effects of stress.

Levels of anticipatory anxiety have also been shown to decrease with routine supplementation. Some people will use L-Tyrosine supplements to help them think more clearly and supporting intellectual abilities.

It is thought that low levels of Epinephrine may play a role in depression, and Dopamine may play a role in the function of antidepressants. It has been hypothesized that supplementing with L-Tyrosine may improve catecholamine levels, possibly helping to lessen the frequency and severity of depressive episodes. No clinical proof exists for this yet, but supplementation has been found to improve overall mood and the perception of happiness.

In addition to serving as the precursor for Dopamine and other neurotransmitters associated with well-being, L-tyrosine can also enhance the signaling capacities of various neuronal pathways.

Because it increases the production of “feel-good” chemicals inside the brain, some people will use L-Tyrosine for low sex drive, erectile dysfunction, lacking motivation, and other related psychological and physical conditions.

The Natural Medicines database has rated supplemental L-Tyrosine as Possible Effective for improving cognitive performance and memory under stressful conditions, and for improving altertness following sleep deprivation. As it is an amino acid, Tyrosine qualifies as a dietary supplement in the US. The FDA has not approved Tyrosine as a drug to prevent or treat any conditions.

L-Tyrosine Side Effects

L-Tyrosine side effects are not experienced by the majority of those who supplement with this amino acid. It is present naturally in the body and can be synthesized from the essential amino acid Phenylalanine.

This supplement is rated as Likely Safe when used orally at dosages commonly found in foods. It is rated Possibly Safe for dosages of up to 150mg/kg of bodyweight per day for a period of up to three months. In some cases, adverse effects including nausea, diarrhea, vomiting, or nervousness have been reported.

Most L-Tyrosine side effects are seen when very high dosages are taken. Results from clinical studies indicates that L-Tyrosine side effects are unlikely at commonly used therapeutic doses.

For most purposes, between 50mg and 100 mg of L-tyrosine is taken either twice or thrice daily. While the risk of side effects may increase with higher dosages, no significant toxicity has been noted, even at daily doses up to 12,000 mg.

There may be some adverse side effects caused by drug interactions when using L-Tyrosine. It may interact with other dopaminergic drugs, including Levodopa (L-Dopa) or the supplement Mucuna Pruriens. It may also interact with medications that affect the thyroid, including thyroid hormones.

To reduce the risk of experiencing L-Tyrosine side effects, it is best to speak with your doctor before beginning supplementation. This is especially true if you have any pre-existing health conditions, or if you are currently taking prescription medications.

Food Sources of L-Tyrosine

For those who wish to raise their Tyrosine levels naturally, certain food sources can be added to the diet. Foods that are high in L-Tyrosine include vegetables that come from the sea (like kelp and seaweed), scallops, seeds, nuts, salmon, sardines, tuna, cod, eggs, poultry and cheese.

It is also possible to raise endogenous Tyrosine levels by increasing intake of foods that contain Phenylalanine. Foods that contain this amino acid include dairy, meat, chicken, eggs, beans, fish, and nuts. The consumption of L-Tyrosine or Phenylalanine from foods is not associated with side effects in the majority of cases.

Trying to raise L-Tyrosine with foods does have a major drawback though. The Tyrosine in food is not able to effectively cross the blood-brain barrier (protective membrane the separates the bloodstream from brain tissue).

Because it uses the same transport channels, Tyrosine from food has to compete with other amino acids in food to enter the brain. The amount of Tyrosine in food that can actually make it to the brain is often low and may not be enough to increase very low levels.

In cases like this, smart supplementation at recommended levels may help increase levels of this amino acid while also avoiding L-Tyrosine side effects.

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