A common amino acid sold as a brain-boosting supplement may shorten men's lives by nearly a year, according to a study of more than 270,000 people in the United Kingdom. Researchers found that higher blood levels of tyrosine were associated with reduced life expectancy in men, while women showed no significant effect.
The study, published in Aging-US, was led by teams from the University of Hong Kong and the University of Georgia. They analyzed data from the UK Biobank, a large health and genetic database. The researchers looked at both phenylalanine and tyrosine, two amino acids involved in metabolism and brain function, to see if they were connected to lifespan.
A surprising sex difference emerges
The findings point to a clear gap between men and women. Higher tyrosine levels were linked to a shorter lifespan in men, potentially reducing life expectancy by nearly a year. In women, no significant effect appeared. This difference raises questions about why aging and longevity vary between sexes, though the researchers caution that much more work is needed before any health advice can be drawn.
Tyrosine is found naturally in protein-rich foods and is also sold as a supplement for focus and mental performance. The body uses it to produce dopamine, a neurotransmitter that helps regulate mood, motivation, and thinking. Phenylalanine, another amino acid in the study, is also present in protein foods and supplements.
How the study worked
The team used two methods to test the connection. First, they looked for associations between blood levels of phenylalanine and tyrosine and outcomes related to death and predicted lifespan. Then they applied a genetic technique called Mendelian randomization, which uses natural genetic differences to test whether a relationship might be causal rather than just a coincidence.
This approach strengthens the evidence that tyrosine itself, not some other factor, may influence how long men live. The researchers noted that scientists still do not fully understand how long-term differences in these amino acids might affect aging.
The results add a new layer to the ongoing conversation about protein intake and supplements. While tyrosine is widely used for its supposed cognitive benefits, this study suggests that for men, higher levels might come with a hidden cost. The findings could eventually help explain why men and women age differently, but translating them into practical recommendations will require further investigation.
