A large study involving more than 270,000 people has linked higher blood levels of the amino acid tyrosine to a shorter lifespan in men. Using both observational data and genetic analysis, researchers found that elevated tyrosine could potentially reduce male life expectancy by nearly a year, while no significant effect appeared in women. Tyrosine is found naturally in protein-rich foods and is also sold as a supplement for boosting focus and mental performance, making the finding especially intriguing.