New research from the UK Biobank suggests that elevated levels of the common amino acid tyrosine may be associated with reduced longevity, particularly in men.

Drawing on data from nearly 272,500 participants, researchers examined blood levels of the amino acids phenylalanine and tyrosine and tracked mortality outcomes over time. Approximately 24,000 deaths were recorded during the study period.

Using advanced genetic analysis, known as Mendelian randomization, the study assessed whether lifelong higher levels of tyrosine might play a causal role in shortening lifespan. The results indicate that genetically predicted higher tyrosine levels were associated with reduced longevity, with men losing roughly one year of life per standard deviation increase in tyrosine. The effect in women was weaker and less consistent.

“Tyrosine is a building block of protein and is essential for producing brain chemicals like dopamine, as well as stress-related hormones,” said the study authors. “Our findings suggest that the balance of specific amino acids, rather than total protein intake alone, may influence how we age.”

Phenylalanine, which can be converted into tyrosine in the body, did not independently predict lifespan once tyrosine levels were accounted for, positioning tyrosine as the primary factor in this association.

While the precise mechanisms remain under investigation, prior research suggests that amino acids like tyrosine may interact with nutrient-sensing pathways, cellular systems that regulate growth, repair, and stress responses, which could influence aging processes over decades.

The study also highlights a sex-specific difference, with men showing a stronger association between high tyrosine levels and shorter lifespan. Researchers caution that further studies are needed to understand these differences, including potential roles of hormonal regulation and metabolism.

Importantly, the study does not suggest eliminating protein from the diet or making abrupt dietary changes. Instead, it emphasizes the potential long-term impact of amino acid balance on health and aging.

This research marks a significant step toward understanding how microscopic biochemical factors, such as amino acids circulating in the blood over a lifetime, may shape human longevity and opens avenues for more personalized approaches to nutrition and aging interventions.