A large new study suggests that men with higher blood levels of tyrosine — an amino acid found naturally in protein-rich foods and sold in some “focus” supplements — may, on average, live slightly shorter lives. The research, based on data from more than 270,000 UK Biobank participants, found the clearest signal in men, not women. The study was led by Jie V. Zhao, Yitang Sun, Junmeng Zhang and Kaixiong Ye of the University of Hong Kong and the University of Georgia. Researchers examined two related amino acids, phenylalanine and tyrosine, using both standard observational analysis and Mendelian randomization, a genetic method used to test whether an association may be more likely to reflect cause rather than simple correlation.
At first glance, both amino acids appeared linked to a higher risk of death. But after deeper analysis, tyrosine was the only one that remained consistently associated with reduced lifespan, especially in men. In the study’s multivariable genetic model, higher tyrosine was associated with about 0.91 fewer years of life in men; the effect was not statistically meaningful in women. The authors concluded that “reducing tyrosine in people with elevated concentrations may contribute to prolonging lifespan,” while stressing that the effect may be sex-specific.
The researchers also found that men generally had higher tyrosine levels than women, which may help explain part of the long-observed life-expectancy gap between the sexes. By contrast, phenylalanine showed no association with lifespan in either men or women after controlling for tyrosine, suggesting tyrosine may be the more important driver.
Tyrosine matters biologically because it helps the body make dopamine and other neurotransmitters, which is one reason it is often marketed for focus or cognitive performance. But the new research did not test tyrosine supplements directly, and it does not show that eating normal protein-rich foods is dangerous. Instead, it raises a more specific question: whether chronically elevated circulating tyrosine could influence metabolism, insulin resistance, or other aging-related pathways differently in men and women. The paper’s authors say more work is needed before anyone should change diet or supplement use based on this study alone. Still, the findings add to growing evidence that nutrition and longevity may not work the same way in men and women that some widely used compounds may deserve closer long-term scrutiny.
