A common "focus" amino acid was linked to nearly a year of lost lifespan in men

Tyrosine is an amino acid marketed in countless "focus" and pre-workout supplements for its role in producing dopamine, norepinephrine and epinephrine — the neurotransmitters behind mood, attention and the body’s stress response. A large 2025 study using UK Biobank data found a less flattering side to the story: higher blood tyrosine was consistently linked to shorter lifespan, specifically in men.

How the study was designed

Researchers from the University of Hong Kong and the University of Georgia analyzed health and genetic data from more than 270,000 UK Biobank participants, examining whether two related amino acids — phenylalanine and tyrosine — influenced lifespan. They used two complementary methods: observational analysis of amino acid levels against mortality, and Mendelian randomization, a genetic technique that helps distinguish a plausible cause-and-effect relationship from simple correlation.

What they found

Both amino acids initially appeared linked to higher mortality risk, but after more detailed analysis, only tyrosine held up as a consistent, independent predictor. Genetic analysis estimated that elevated tyrosine could shorten men’s lifespan by close to one year — with no equivalent association found in women. The researchers note men generally carry higher tyrosine levels than women, a difference that may partly explain some of the long-observed lifespan gap between the sexes.

"Phenylalanine showed no association with lifespan in either men or women after controlling for tyrosine" — leaving tyrosine as the specific signal of interest.

What might explain the effect

The mechanism isn’t settled. Candidate explanations include tyrosine’s links to insulin resistance (itself tied to diabetes and cardiovascular disease risk) and its role feeding stress-response neurotransmitter pathways that may behave differently by sex due to hormonal factors. Reducing overall protein intake was noted as one plausible way to lower blood tyrosine, though this hasn’t been tested as an intervention.

What this doesn’t prove

Crucially, the study measured naturally occurring blood tyrosine levels, not supplemental tyrosine intake or dosing — it is not a trial of tyrosine supplements, and the authors are explicit that this shouldn’t be read as proof that supplementing is harmful. It’s a genetic-epidemiology signal worth further study, not a verdict. Given the uncertainty, this is a case for tracking your actual protein and amino acid intake rather than reflexively adding another "brain supplement" on top of an already adequate diet.

Misi’s nutrition insights track total protein and food-sourced amino acid patterns rather than treating any single supplement as a free pass — useful context if you’re weighing a tyrosine-containing stack against simply hitting your protein target through whole foods.