A study of over 270,000 people suggests elevated levels of the amino acid tyrosine may be associated with reduced life expectancy in men, though no such effect was found in women.

Researchers from the University of Hong Kong and the University of Georgia have identified a potential link between higher levels of the amino acid tyrosine and shorter lifespans in men. Analyzing data from more than 270,000 participants in the UK Biobank, the study found that elevated tyrosine concentrations may reduce male life expectancy by nearly one year. No significant association between tyrosine levels and lifespan was observed in women.

Research Methodology and Findings

The research team employed both observational analysis and Mendelian randomization, a genetic method used to investigate potential causal relationships. While initial data suggested both phenylalanine and tyrosine were associated with an increased risk of death, further examination revealed that tyrosine remained the primary factor after controlling for other variables. Phenylalanine showed no independent association with lifespan in either sex once tyrosine levels were accounted for. Men were found to have higher baseline levels of tyrosine than women. While this difference could theoretically relate to the existing gap in average lifespan between the sexes, the study does not confirm that tyrosine is the cause of that disparity.

Potential Biological Mechanisms

Scientists have proposed several hypotheses to explain why tyrosine might impact longevity in men but not women. One possibility involves insulin resistance, which is linked to age-related diseases. Another theory suggests that because tyrosine is used to produce neurotransmitters involved in the body's stress response, differences in how men and women process these hormones could account for the observed variation in lifespan effects. These mechanisms remain speculative and require further study. The researchers emphasized that the study did not directly test tyrosine supplements, meaning the findings do not prove that taking such supplements shortens lifespan. Consequently, there are currently no health recommendations regarding tyrosine intake based on this research.