An amino acid that is a common ingredient in brain and focus supplements is linked to a shorter lifespan in men, according to a large new study published in the journal Aging-US.
Researchers analyzed health and genetic data from more than 270,000 participants in the UK Biobank to test whether certain amino acids influence how long people live. Their findings point to tyrosine, a nutrient often promoted for mental performance and stress support.
What the study found
Men with higher levels of tyrosine in their blood had a shorter life expectancy, with genetic estimates suggesting a loss of close to a year. No meaningful association appeared in women.
Tyrosine is one of the building blocks the body uses to make chemical messengers such as dopamine and adrenaline. Supplements containing it are sold widely as a way to sharpen focus, lift alertness and cope with stressful periods.
The team also looked at phenylalanine, another amino acid that the body converts into tyrosine. It showed no link to lifespan once tyrosine levels were taken into account.
Why only men?
The reason for the sex difference is not yet clear. Men tend to carry higher tyrosine levels than women, which may help explain why the effect showed up only in men, the researchers said.
Hormone-related differences between men and women could also play a role in how the body processes the amino acid over a lifetime.
What it means for supplements
The study has limits. It measured naturally occurring tyrosine in the blood and did not test supplements directly, so it cannot prove that taking tyrosine shortens anyone's life.
The authors stress that tyrosine is essential for normal brain and body function and that people should not avoid protein-rich foods such as meat, fish, eggs and dairy, which provide it.
Still, the findings add to a growing list of cases where widely marketed supplements outrun the evidence about their long-term effects. For men who take tyrosine products daily to boost focus, the study is a reason to review the habit with a doctor.