It's easy to boost your intake of the amino acid L-tyrosine, also known simply as tyrosine, by eating more of certain common protein-rich foods. But keep in mind that there's limited evidence that higher L-tyrosine levels are beneficial.
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What's Essential, What's Not
Amino acids like L-tyrosine are crucial to human existence. As the U.S. National Library of Medicine (NLM) notes, amino acids come together to form proteins.
And the reverse comes into play: You eat foods that include proteins, and your body then breaks them back down into the original amino acids. The body then uses the amino acids to produce new proteins that play a part in important body functions, such as processing food, repairing tissue and creating energy. They even help you grow.
L-tyrosine is considered a "non-essential amino acid," according to NLM, but that doesn't mean you don't need it. Instead, it means your body already makes it, and it doesn't have to come directly from food or supplements.
"Our bodies can break down proteins into amino acids, rearrange them and make L-tyrosine," says Isabel Maples, MEd, RDN, a dietitian in the Washington, DC, area and a spokesperson for the Academy of Nutrition and Dietetics. "Specifically, the amino acid phenylalanine can be made into L-tyrosine."
The other non-essential amino acids are alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline and serine, notes the NLM.
In addition, there are nine other "essential amino acids" that you get from food because you can't make them yourself.
Read more: List of Foods That Contain the Most Amino Acids
Supplements or Foods?
One way to raise L-tyrosine levels would be to take supplements. But, "supplements can be pricey, and they don't make up for a balanced diet," Maples explains. "Focus first on getting enough protein from a variety of sources."
She suggests eating non-meat protein sources to boost L-tyrosine levels, watching their saturated fat levels so you don't consume too much. Consider:
- Dairy foods (eat three servings a day of milk, yogurt or cheese)
- Seafood (eat fish or shellfish at least twice a week)
- Dried beans, peas and lentils
- Nuts and seeds
The Need for L-tyrosine
Though you could try to boost your intake of L-tyrosine, do you really need to? Research has produced mixed results. "Studies with L-tyrosine show some benefit on mental functions, such as memory and alertness during times of physical stress, like when people are exposed to extreme cold or are sleep-deprived," Maples says. "This is not the same as emotional stress, however."
If you aim to be more alert, then, more L-tyrosine may be helpful. However, although generally considered safe, recommended dosages have not been set by the Food and Drug Administration (FDA).
On other fronts, Maples says that "emerging research shows there could be some benefit to L-tyrosine during heroin withdrawal, though it was studied in combination with other factors."
Studies have not shown benefits for taking L-tyrosine to boost exercise performance in cyclists and runners, she says, nor has it been shown to affect attention-deficit/hyperactivity disorder (ADHD) or depression.
When to Limit L-tyrosine
Boosting L-tyrosine in your diet by eating more protein is generally safe, Maples says, but there are some exceptions. People with kidney disease often need to control their protein intake in order to protect their kidneys from overwork, according to the National Kidney Foundation. Check with your physician if you have kidney disease before changing your diet.
Also, people with phenylketonuria (PKU), a rare metabolic disorder, need to carefully monitor their protein intake, according to Stanford Children's Health. Those with the disease can't properly process the amino acid phenylalanine, which produces L-tyrosine.
"Babies in the U.S. and many other countries are tested for PKU right after birth," Maples says. "Treatment includes a diet low in phenylalanine through eliminating some foods with protein, so L-tyrosine supplements play an important role. Also, there are foods with L-tyrosine that are available via medical prescription."
Read more: The Recommended Dosage for L-Tyrosine
It seems that, unless you have a medical reason for limiting protein intake, L-tyrosine supplements are not necessary, and — for the most part — eating a healthy diet that includes protein is all that you need.
- Isabel Maples, MEd, RDN, dietician, Washington D.C., and spokesperson, Academy of Nutrition and Dietetics
- National Library of Medicine: “Amino Acids”
- FDA: “CFR - Code of Federal Regulations Title 21 (Tyrosine)”
- National Kidney Foundation: “Nutrition and Early Kidney Disease (Stages 1–4)”
- Stanford Children’s Health: “Defects in Metabolism of Amino Acids: PKU”