Scientists reporting in the journal Aging-US examined whether two amino acids, phenylalanine and tyrosine, could influence how long people live (lifespan). Their findings suggest that higher levels of tyrosine in the blood are associated with a shorter life expectancy in men, raising new questions about the role this nutrient may play in aging.

The research was conducted by Jie V. Zhao, Yitang Sun, Junmeng Zhang, and Kaixiong Ye of the University of Hong Kong and the University of Georgia.

What Are Phenylalanine and Tyrosine?

Amino acids are often described as the building blocks of proteins. The body uses them to create and repair tissues, produce enzymes, and support countless biological functions.

Phenylalanine and tyrosine are two amino acids that help regulate metabolism and brain activity. They are naturally present in many foods, particularly meat, fish, eggs, dairy products, and other protein rich sources. They are also available in dietary supplements marketed for energy, focus, and cognitive performance.

Tyrosine is especially notable because it helps the body produce neurotransmitters such as dopamine, norepinephrine, and epinephrine. These chemical messengers play important roles in mood, attention, motivation, memory, and the body's response to stress.

Because of these functions, tyrosine has attracted growing interest among researchers studying aging, brain health, and lifespan.

Study Analyzed More Than 270,000 People

To investigate whether these amino acids affect longevity, the researchers analyzed health and genetic information from more than 270,000 participants enrolled in the UK Biobank, one of the world's largest long term health databases.

The team used two complementary approaches. First, they examined observed relationships between amino acid levels and mortality. They also used a technique called Mendelian randomization, a genetic method that helps scientists determine whether an observed association may reflect a cause and effect relationship rather than simple coincidence.

This combination allowed the researchers to look beyond correlations and gain stronger evidence about whether amino acid levels could directly influence lifespan.

Tyrosine Stood Out as a Potential Longevity Risk

At first glance, both phenylalanine and tyrosine appeared to be associated with a higher risk of death. However, after accounting for additional factors and conducting more detailed analyses, only tyrosine continued to show a consistent relationship with lifespan.

The findings suggested that higher tyrosine levels may contribute to reduced life expectancy in men.

Based on genetic analyses, the researchers estimated that elevated tyrosine levels could shorten men's lifespan by nearly one year.

Women did not show the same pattern. The study found no significant association between tyrosine levels and lifespan among female participants.

The researchers also noted that men generally have higher tyrosine levels than women, which may help explain part of the long observed difference in average lifespan between the sexes.

"Phenylalanine showed no association with lifespan in either men or women after controlling for tyrosine."

Why Might Tyrosine Affect Aging?

Scientists do not yet know exactly how tyrosine might influence lifespan, but several possibilities have emerged.

One potential explanation involves insulin resistance, a condition in which the body's cells become less responsive to insulin. Insulin resistance is linked to numerous age related health problems, including type 2 diabetes, cardiovascular disease, and metabolic disorders.

Tyrosine may also affect the production of neurotransmitters involved in the body's stress response. Over time, disruptions in these systems could potentially influence long term health and aging.

Researchers suspect that hormone related pathways may also play a role. Because these biological pathways can function differently in men and women, they may help explain why the apparent lifespan effect was observed only in men.

What Does This Mean for Supplements?

Tyrosine is frequently marketed as a supplement that may help support concentration, mental performance, and alertness, particularly during stressful situations.

However, the new findings suggest there may be more to the story when considering long term health.

Importantly, the researchers did not directly examine tyrosine supplements or test whether taking supplemental tyrosine shortens lifespan. Instead, the study focused on naturally occurring blood levels of the amino acid and how those levels were associated with longevity.

As a result, the findings should not be interpreted as proof that tyrosine supplements are harmful. Nevertheless, they do suggest that elevated tyrosine levels could be worth further investigation.

The researchers note that dietary strategies such as reducing overall protein intake may help lower tyrosine levels. Future studies will be needed to determine whether such approaches can safely improve healthy aging and lifespan.

More Research Is Needed

While the study provides some of the strongest evidence so far linking tyrosine to longevity, many questions remain unanswered.

Scientists will need to confirm the findings in additional populations and better understand the biological mechanisms involved. Researchers also hope to learn whether diet, lifestyle changes, or other interventions can safely reduce tyrosine levels and potentially promote healthier aging.

For now, the study highlights an intriguing possibility: a nutrient best known for supporting brain chemistry may also have an unexpected connection to how long people live.