Tyrosine Amino Acid Tied to Shorter Lifespan in Men, Not Women, Study Finds

A large study of more than 270,000 participants in the UK Biobank has found that higher blood levels of the amino acid tyrosine are linked to a shorter lifespan in men, with no similar effect detected in women. The research, led by Jie V. Zhao, Yitang Sun, Junmeng Zhang and Kaixiong Ye of the University of Hong Kong and the University of Georgia, was published in the journal Aging-US.

Tyrosine and a related amino acid, phenylalanine, are found in protein-rich foods and are also sold as dietary supplements. The body uses tyrosine to make neurotransmitters such as dopamine, chemical messengers that help regulate mood, motivation and thinking. The researchers used two approaches: looking for statistical associations between blood levels of the two amino acids and death, and Mendelian randomization, a genetic method that can offer stronger clues about cause and effect than observational data alone.

The genetic analysis suggested tyrosine may have a causal link to reduced life expectancy in men, potentially shortening male lifespan by nearly a year; no such effect showed up in women. The link held even after accounting for phenylalanine, while phenylalanine itself showed no association with lifespan in either sex once tyrosine was factored in. The researchers also found that men generally have higher tyrosine levels than women, though the study does not establish that tyrosine explains the broader lifespan gap between the sexes.

The scientists propose that insulin resistance, or tyrosine's role in stress-related neurotransmitters, could help explain the pattern, though these remain hypotheses requiring further study. Importantly, the researchers did not test tyrosine supplements directly; the results describe natural blood tyrosine levels, not supplementation, and do not show that taking a tyrosine supplement shortens lifespan.