Tyrosine sits on every vitamin-shop shelf as a focus and stress aid you can buy by the bottle. A new UK Biobank analysis of 272,475 people just found that, in men, every one-standard-deviation rise in blood tyrosine tracked with about 0.91 fewer years of life. In women, the same calculation came back as noise. I came in ready to roll my eyes at another supplement scare, and the genetics in this one have teeth.
The paper is out in Aging-US, from researchers at the University of Hong Kong and the University of Georgia, who ran circulating tyrosine against death records across roughly 11 years of follow-up and layered a Mendelian randomization analysis on top. The male causal estimate landed at 0.91 fewer years of life per standard-deviation increase (95% CI, -1.60 to -0.21). The female estimate was smaller and crossed zero. The authors used 45 sex-specific genetic instruments in men and 29 in women, pulled from genes that govern tyrosine synthesis, breakdown, and transport.
Mendelian randomization is what makes this hard to wave off. Variants that nudge your tyrosine level from birth act as natural experiments: you’re randomized at conception into “your DNA pushed your lifetime tyrosine slightly up” or “it didn’t,” and then you live your life. If the up-pushers also track with earlier death, the usual confounders that haunt nutrition studies (diet, exercise, the kind of person who buys focus supplements) become much harder to blame. It isn’t a pill trial and the authors don’t claim it is, but it estimates a lifelong exposure in a way ordinary cohort math can’t.
The observational hazard ratios were modest. For tyrosine, HR 1.03 in men (95% CI 1.01 to 1.05), basically flat in women. Phenylalanine, the precursor your liver converts into tyrosine, looked worse on the surface in both sexes, but when the authors held tyrosine constant in the multivariable MR, phenylalanine’s signal vanished. Tyrosine carried all the weight.
So what is tyrosine doing to men that it isn’t doing to women? The paper doesn’t pretend to have a clean answer, and I respect that. It lays out three plausible threads and lets the reader hold them at once. Higher tyrosine is associated with insulin resistance, which feeds the chronic metabolic diseases that kill men earlier than women. Tyrosine is also the building block for catecholamines, the adrenaline-family neurotransmitters that drive the stress response, a system that runs harder and shorter in men. And those neurotransmitters are themselves modulated by sex hormones. Pull on any one of those threads and you reach the other two.
About the supplement, plainly: the researchers didn’t test pills. They measured plasma tyrosine in fasting blood samples, not capsules swallowed on the way to work. You can argue that a 500 mg dose on a Tuesday isn’t the same thing as a lifelong genetically nudged baseline, and the authors say so themselves. But your blood is what your tissues actually see, and the finding is that men whose blood carries more tyrosine die sooner. The pitch on the bottle, that tyrosine feeds dopamine and norepinephrine and therefore feeds focus, was always a long leap from biochemistry to clinical effect: marketing logic, not a settled cognitive benefit.
A note on the receipts. The work was funded by the NIH National Institute of General Medical Sciences and Hong Kong’s InnoHK program, and the authors disclosed no competing interests. The usual “follow the money” reflex points in directions the supplement marketing departments will not enjoy.
What would I do with this? Personally, if you’re a man taking daily tyrosine for focus, I’d stop pretending the lifespan question is theoretical and bring it up at your next physical, including a look at fasting metabolic markers, because the insulin-resistance thread is the most actionable of the three. The signal here is male-specific, so women get a softer answer, not a clean bill of health: the analysis simply didn’t detect a longevity effect in 272,475 people, and I’d want to see it replicated in non-European cohorts before I treated that absence as final. And I’d love to see a supplement-aisle label that reflected what the best causal-inference tools we have are now saying out loud.
Sources
- Aging-US: Zhao, Sun, Zhang, Ye. “The role of phenylalanine and tyrosine in longevity: a cohort and Mendelian randomization study” (2025)
- PubMed entry for Zhao et al. (PMID 41045493)
- Aging-US press release: “High Tyrosine Levels Linked to Shorter Lifespan in Men”
- ScienceDaily coverage of the Aging-US study (June 15, 2026)
- News-Medical summary of the UK Biobank tyrosine analysis