Research & Education

Tyrosine – An Amino Acid Worth Exploring

Like almost any nutrient be it a vitamin mineral or botanical extract amino acids are best introduced to the body via whole foods. In this way they typically come packaged along with complementary and accessory nutrients that facilitate their absorption and fulfillment of their biochemical destinies. (It’s so nice of nature to do that for us isn’t it?) But in just the same way that certain disease states both acute and chronic can increase the body’s need for particular vitamins and minerals above the levels someone would reasonably get from food alone certain conditions may warrant supplemental amounts of amino acids. 

There’s branched chain amino acids for potential skeletal muscle growth tryptophan (and its metabolite 5-HTP) for lifting a low mood or helping to promote sleep and glutamine for gut health and tissue healing and repair after trauma.

What about tyrosine?

Like its aromatic amino acid brethren (phenylalanine and tryptophan) tyrosine is a building block for neurotransmitter synthesis. Unlike phenylalanine and tryptophan however tyrosine is not technically an essential amino acid since it can be synthesized from phenylalanine. (For individuals with phenylketonuria [PKU] tyrosine is essential as they lack the enzyme that facilitates this conversion.)

Tyrosine readily crosses the blood-brain barrier and is the starting point for producing L-DOPA dopamine epinephrine and norepinephrine. Tyrosine is also the building block for thyroxine (a.k.a. T4 or thyroid hormone) but inadequate tyrosine is usually not the limiting factor in thyroxine synthesis. Individuals with suboptimal thyroid function might benefit from supplemental tyrosine but likely only if hypothyroid symptoms are due primarily to insufficient tyrosine availability. Owing to its role in neurotransmitter and catecholamine synthesis tyrosine has shown benefit for alleviating depression acute stress narcolepsy and cocaine addiction. (With regard to cocaine addiction tyrosine and tryptophan may be an effective combination with these amino acids blunting the cocaine “high” and reducing the depression that may result from drug withdrawal.)

Tyrosine competes with other large neutral amino acids (phenylalanine tryptophan leucine isoleucine valine and methionine) for transport across the blood-brain barrier so for optimal efficacy supplemental tyrosine is best taken on an empty stomach or perhaps with a carbohydrate-containing meal or snack that is low in protein. Taking vitamin B6 along with tyrosine may facilitate the conversion of tyrosine to dopamine as the vitamin is a cofactor for the aromatic amino acid decarboxylase enzyme that catalyzes the reaction.

Considering tyrosine’s role as a precursor to dopamine and thyroid hormone it would seem that tyrosine supplementation would be a slam dunk for improving depression. Yet results are mixed. Randomized double-blind placebo-controlled studies have failed to show efficacy for tyrosine with regard to depression; nevertheless anecdotal evidence indicates there may be a role so it’s possible it depends on an individual patient’s presentation. Depression is multifactorial so there may be cases where supplemental tyrosine will help alleviate symptoms and others where the issue is unrelated to inadequate tyrosine.

On the other hand tyrosine may be helpful for supporting cognitive function in acutely stressful situations. A review looking at the effects of tyrosine on behavior and cognition found that “tyrosine loading acutely counteracts decrements in working memory and information processing that are induced by demanding situational conditions such as extreme weather or cognitive load.” Most likely this is due to the influence of tyrosine on restoring healthy brain catecholamine levels. Other researchers had similar findings—that tyrosine does enhance cognitive performance particularly in short-term stressful and cognitively demanding situations. One study’s authors caveated this by saying that tyrosine “is an effective enhancer of cognition but only when neurotransmitter function is intact and DA [dopamine] and/or NE [norepinephrine] is temporarily depleted.”

Fortunately tyrosine is an inexpensive compound to supplement with so patients may be inclined to give it a try if their health care professionals suspect some of the symptoms they present with may be related to suboptimal tyrosine and/or reduced levels of hormones and neurotransmitters that come from tyrosine.

Note that tyrosine should not be supplemented in pregnant or lactating women nor in individuals taking MAOIs for depression. Individuals with Parkinson’s disease may benefit from supplemental tyrosine for the production of dopamine but tyrosine should not be taken at the same time as levodopa due to possible reduction in the drug’s efficacy.