A widely consumed amino acid found in protein-rich foods and many cognitive enhancement supplements may be associated with shorter lifespans in men, according to a new study. Researchers found that higher blood levels of tyrosine were linked to a modest reduction in life expectancy among men, while no similar association was observed in women.
The study, published in Aging-US, examined whether the amino acids phenylalanine and tyrosine influence human longevity. Led by researchers from the University of Hong Kong and the University of Georgia, the findings contribute to ongoing discussions about protein intake, dietary supplements, and healthy aging.
The Role of Phenylalanine and Tyrosine
Amino acids are the building blocks of proteins and are essential for tissue repair, hormone production, and numerous metabolic processes. Phenylalanine and tyrosine are closely related amino acids involved in regulating metabolism and supporting normal brain function.
Both are naturally abundant in foods such as meat, fish, eggs, and dairy products, and they are also common ingredients in supplements marketed to improve energy, focus, and cognitive performance.
Tyrosine serves as a precursor for several important neurotransmitters, including dopamine, norepinephrine, and epinephrine, which help regulate mood, attention, and the body’s response to stress.
Because of its role in brain chemistry, tyrosine has been widely studied for its potential to enhance cognitive performance and reduce the effects of sleep deprivation. The new study instead investigated whether chronically elevated tyrosine levels might influence long-term survival.
How the Study Was Conducted
The researchers analyzed health, biochemical, and genetic information from more than 270,000 participants enrolled in the UK Biobank, a large long-term study that tracks health outcomes over time. Blood concentrations of phenylalanine and tyrosine were compared with mortality data.
To strengthen their findings beyond simple associations, the researchers also used Mendelian randomization, a genetic approach that takes advantage of inherited genetic variants associated with amino acid levels. Because these genetic differences are established at conception, the method can provide stronger evidence about whether a biological factor may contribute to disease risk or longevity.
By combining observational and genetic analyses, the researchers sought to determine whether phenylalanine or tyrosine might play a direct role in lifespan rather than simply reflecting dietary habits or underlying health conditions.
Tyrosine Was Linked to Shorter Lifespan in Men
Initial analyses indicated that higher levels of both phenylalanine and tyrosine were associated with increased mortality. However, after adjusting for multiple potential confounding factors and accounting for the close relationship between the two amino acids, only tyrosine remained consistently associated with reduced longevity.
Using genetic analyses, the researchers estimated that men genetically predisposed to higher tyrosine levels could experience an average reduction in lifespan of nearly one year. No statistically significant association was observed among women.
The researchers also noted that men generally have higher circulating tyrosine levels than women. They suggest this biological difference could contribute, at least in part, to the longstanding difference in average life expectancy between men and women.
Possible Biological Mechanisms
The biological mechanisms underlying the association remain unclear. One possible explanation involves insulin resistance, a condition in which the body’s cells become less responsive to insulin, increasing the risk of type 2 diabetes, cardiovascular disease, and other age-related disorders.
Previous research has linked elevated levels of aromatic amino acids, including tyrosine, with a greater risk of insulin resistance and cardiometabolic disease. If tyrosine contributes to these metabolic pathways, it could indirectly influence lifespan by increasing the likelihood of chronic disease, particularly among men.
The researchers also suggest that tyrosine’s involvement in neurotransmitter production and stress hormone regulation could influence cardiovascular function, inflammation, and other biological processes involved in aging. These mechanisms may differ between men and women and warrant further investigation.
What the Findings Mean for Tyrosine Supplements
Tyrosine supplements are widely marketed as nootropics and performance-enhancing products designed to improve concentration, alertness, and cognitive performance during stressful situations. The new findings raise questions about whether maintaining chronically elevated tyrosine levels is beneficial over the long term, particularly for men.
However, the researchers emphasize that their study did not examine the effects of tyrosine supplementation directly. Instead, it evaluated naturally occurring blood concentrations and genetically influenced differences in tyrosine levels.
As a result, the findings do not demonstrate that taking tyrosine supplements shortens lifespan, nor do they establish a safe or unsafe dosage. Rather, they suggest that persistently elevated tyrosine exposure over many years deserves additional investigation.
Diet, Protein Intake, and Future Research
The authors note that overall dietary patterns, including total protein intake and protein sources, can influence circulating tyrosine levels. They suggest that modifying protein intake or adjusting the balance of dietary amino acids could potentially reduce tyrosine concentrations.
However, they emphasize that any such dietary recommendations require careful study. Adequate protein intake remains essential for maintaining muscle mass, immune function, and healthy aging, particularly in older adults. Experts caution against making major dietary changes based on the findings of a single study.
Future research will seek to replicate these results in other populations, investigate the biological mechanisms linking tyrosine with age-related disease, and determine whether dietary or lifestyle interventions can safely modify tyrosine levels without compromising overall health.
The findings highlight the complexity of human nutrition and aging. Although tyrosine plays an important role in brain function and metabolism, the study suggests that chronically elevated levels may also have unintended consequences for long-term health, particularly in men.
