Can You Take Phenylalanine and Tyrosine Together? The Full Breakdown

January 7, 2026 •

4 min read

For healthy individuals, a balanced diet provides both phenylalanine and tyrosine, two amino acids that are naturally and safely consumed together. The question of whether you can take phenylalanine and tyrosine together as supplements requires understanding their deep metabolic connection and potential for competitive inhibition at high doses.

Quick Summary

Phenylalanine is converted to tyrosine in the body, and both are precursors for vital neurotransmitters. Co-supplementing requires considering individual health, metabolic pathways, and potential competition, particularly in individuals with PKU.

Key Points

Natural Pairing: Phenylalanine is converted into tyrosine in the body, so consuming them together via food is a natural process for most people.
Key Precursors: Both amino acids are essential for producing neurotransmitters like dopamine and norepinephrine, which affect mood and brain function.
PKU is a Critical Exception: Individuals with phenylketonuria (PKU) cannot process phenylalanine, making combined intake from supplements extremely dangerous and requiring a very specific diet.
Competitive Inhibition Risk: In high doses, phenylalanine and tyrosine compete for transport across the blood-brain barrier, which can reduce the effectiveness of both.
Diet Over Supplements: For most healthy individuals, a balanced, protein-rich diet is the best and safest way to ensure adequate intake of both amino acids.

The Intertwined Metabolism of Phenylalanine and Tyrosine

Phenylalanine is an essential amino acid, meaning the human body cannot produce it and must obtain it from dietary protein. In a critical metabolic step, the liver enzyme phenylalanine hydroxylase converts phenylalanine into tyrosine, a non-essential amino acid. This process is the body's primary way of metabolizing excess phenylalanine and providing the raw materials for tyrosine. When you consume protein-rich foods, you are naturally ingesting both amino acids simultaneously.

The Importance of the Conversion

The efficient conversion of phenylalanine to tyrosine is vital. A congenital metabolic disorder called phenylketonuria (PKU) results from a defective phenylalanine hydroxylase enzyme, which blocks this conversion. This leads to a dangerous buildup of phenylalanine in the body, which can cause severe health issues, including brain damage. For individuals with PKU, a strict, low-phenylalanine diet is necessary, and tyrosine is an essential nutrient they must consume, often through medical foods.

Impact on Brain Neurotransmitters

Beyond protein synthesis, both phenylalanine and tyrosine serve as precursors for a group of brain chemicals called catecholamines. This pathway includes:

Dopamine: Regulates mood, attention, motivation, and motor control.
Norepinephrine (Noradrenaline): Important for alertness, memory, and the body's 'fight or flight' response.
Epinephrine (Adrenaline): Also involved in the stress response.

Since phenylalanine is used to make tyrosine, and tyrosine is then used to create these neurotransmitters, sufficient intake of either or both can support this pathway. Some research, especially in controlled settings like cold or sleep-deprived states, has suggested that tyrosine supplementation can enhance cognitive performance and reduce the effects of stress. However, this is largely dependent on the individual's existing levels and specific needs.

Phenylalanine vs. Tyrosine: A Comparison


Feature	Phenylalanine (Phe)	Tyrosine (Tyr)
Essentiality	Essential amino acid (must be obtained from diet).	Non-essential amino acid (can be made from Phe).
Primary Role	Protein building block; precursor for Tyrosine.	Protein building block; precursor for catecholamines, thyroid hormones, and melanin.
Dietary Sources	Meats, eggs, dairy, soy, nuts, and seeds.	Meats, dairy, fish, nuts, avocados, and seeds.
Special Considerations	Toxic buildup in individuals with PKU.	Necessary supplementation for individuals with PKU.
Supplementation	Not recommended for PKU. High doses may compete with other large neutral amino acids.	Potentially useful for stress-related cognitive decline, but requires medical guidance.

Safety and Considerations for Supplementation

For most healthy people, consuming a diet rich in protein provides adequate amounts of both phenylalanine and tyrosine. The body's natural regulatory mechanisms ensure a proper balance, and separate supplementation is typically unnecessary and, in some cases, can be counterproductive. When considering supplements, several factors must be addressed.

Competition and Absorption

Phenylalanine and tyrosine are both large neutral amino acids (LNAAs) and compete for transport across the blood-brain barrier. This means that a high dose of one could potentially reduce the uptake of the other and other LNAAs, like tryptophan, which is a precursor for serotonin. This is one of the main reasons dietary sources are preferred for maintaining a healthy balance.

Contraindications and Medical Conditions

Tyrosine can increase levels of thyroid hormone precursors. For this reason, individuals with hyperthyroidism or Graves' disease should avoid tyrosine supplementation. Additionally, tyrosine may interact with monoamine oxidase inhibitors (MAOIs), a class of antidepressant medications, and co-administration is contraindicated. Anyone on medication should consult a healthcare provider before starting any new supplement.

Food Sources Rich in Phenylalanine and Tyrosine

Getting these amino acids from food is the safest and most efficient method for most people. Protein-rich foods are the best sources:

Animal Products: Meat, fish, poultry, eggs, milk, and cheese.
Plant-Based Sources: Soy products (tofu, tempeh), nuts, seeds (especially sesame), and legumes.

Conclusion: Can You Take Phenylalanine and Tyrosine Together?

Yes, in the context of a normal diet, you naturally take phenylalanine and tyrosine together, as phenylalanine is converted into tyrosine within the body. However, deliberately co-supplementing with high doses is generally not recommended for most healthy people and should be approached with caution and medical supervision. The body has a complex system for regulating the balance of these amino acids, and excessive supplementation can interfere with this delicate equilibrium. For individuals with the rare genetic disorder PKU, it is critical to manage phenylalanine intake strictly and ensure adequate tyrosine consumption under a doctor's care. For those seeking cognitive or mood benefits, addressing the root cause through diet and lifestyle is often more effective than relying on high-dose supplements. Always consult a healthcare professional to determine if supplementation is appropriate for your specific needs.

For more information on the intricate metabolism of these amino acids and potential disorders, consult the National Center for Biotechnology Information at the National Institutes of Health.

Frequently Asked Questions

For most healthy people, it is generally unnecessary and potentially counterproductive to take high doses of both supplements together. They compete for absorption and transport, and a balanced diet typically provides sufficient amounts. Medical consultation is recommended before starting supplementation.

Phenylalanine is an essential amino acid and a precursor for tyrosine. Tyrosine, in turn, is a precursor for important neurotransmitters (dopamine, norepinephrine) and hormones (thyroid), which regulate mood, stress response, and metabolic function.

Yes, for individuals with phenylketonuria (PKU), supplementation with phenylalanine is extremely dangerous. They lack the enzyme to convert phenylalanine to tyrosine, causing toxic buildup. These individuals must follow a medically supervised, low-phenylalanine diet and may need tyrosine supplements.

Since both contribute to the production of mood-regulating neurotransmitters, a healthy balance is important. Some studies suggest tyrosine may help with cognitive performance under stress, but high, unbalanced doses could potentially interfere with brain chemistry.

Excellent food sources include high-protein animal products such as meat, eggs, and dairy, as well as plant-based options like soy, nuts, and seeds.

Yes, tyrosine supplementation is contraindicated for individuals taking monoamine oxidase inhibitors (MAOIs). Always consult a doctor or pharmacist about potential interactions with any medications you are taking.

While unlikely from diet alone for healthy people, excessive intake from supplements can lead to an amino acid imbalance and affect neurotransmitter synthesis. For PKU patients, excessive phenylalanine is toxic.