A blood amino acid linked to a shorter life in men

Can the level of one amino acid in your blood affect how long you live?

Maybe, and the effect appears stronger in men. In this study of more than 270,000 adults, higher blood levels of tyrosine, a common amino acid, were linked to a shorter lifespan, with men losing nearly a full year of life. The same pattern was much weaker in women and did not reach statistical significance.

Tyrosine is a building block your body uses to make proteins. You get it from food and also make it from another amino acid called phenylalanine. Both are found in protein-rich foods like meat, eggs, and dairy. Scientists have long known that eating less protein can extend lifespan in animals. This study set out to find which specific amino acids might be driving that effect in people.

What the data show

The researchers analyzed data from the UK Biobank, a large health database with information on hundreds of thousands of British adults. They found that people with higher blood tyrosine tended to die sooner. To test whether tyrosine actually causes a shorter life, rather than just travels alongside it, they used a method called Mendelian randomization. This approach uses natural genetic differences as a kind of built-in experiment, which helps separate cause from coincidence.

The genetic analysis pointed the same direction. After accounting for phenylalanine, higher tyrosine was tied to about 0.91 fewer years of life in men, with a range of 1.60 fewer years to 0.21 fewer years. In women, the loss was smaller, about 0.36 years, and the result was not statistically reliable. Phenylalanine, on its own, showed no link to lifespan in either men or women once tyrosine was taken into account.

Dr. Kumar’s Take

What I find compelling here is the use of Mendelian randomization. Observational studies alone can only show that two things travel together, not that one causes the other. By adding a genetic approach, the authors build a stronger case that tyrosine itself may be part of the problem, not just a bystander. That is a meaningful step up in confidence.

Still, I want to be honest about the limits. This is one study in a mostly white British population, and the female result was not strong enough to hang conclusions on. I would not start fearing protein based on this. Tyrosine is essential, and most of us are nowhere near the levels that seem to matter here. The interesting question is whether people with genuinely high tyrosine could benefit from lowering it.

How strong is the evidence?

The strength of this work comes from combining two different methods that point to the same answer. The observational part draws on a very large group, which makes small effects easier to detect. The Mendelian randomization part uses genetics to reduce the usual problem of confounding, where some hidden factor like diet or wealth secretly drives both the amino acid level and the death rate.

The authors also used a more advanced version of the method, called multivariable Mendelian randomization, to untangle tyrosine from its close partner phenylalanine. This let them show that tyrosine carried the signal while phenylalanine did not. The clear sex difference is intriguing and the authors say it deserves more study. We do not yet know why men appear more affected.

Practical Takeaways

Do not cut healthy protein from your diet based on this single study, since tyrosine is an essential amino acid your body needs and most people sit well below the levels of concern.
If you have had blood metabolic testing that flagged high tyrosine, bring it up with your doctor rather than acting on your own.
Focus on proven longevity habits like steady sleep, regular movement, and whole foods, which have far stronger evidence behind them than any single amino acid.
Watch for future research, especially trials that test whether actively lowering tyrosine in high-level individuals changes health outcomes.

FAQs

What foods are high in tyrosine and phenylalanine?

Both amino acids are common in protein-rich foods, including chicken, fish, eggs, dairy products, soy, nuts, and seeds. Your body can also make tyrosine from phenylalanine, so the two are closely linked. This study does not suggest avoiding these foods, since they provide many nutrients your body needs. The blood levels that mattered in the research reflect a mix of diet, genetics, and how your body processes these amino acids, not just what you ate yesterday.

Why would tyrosine affect men more than women?

The honest answer is that we do not yet know. The study found a clear and statistically reliable link in men but only a weak, uncertain signal in women. Differences in hormones, body composition, or how each sex processes amino acids could play a role. The authors specifically call for more research into these sex-specific pathways, which means this is an open question rather than a settled fact.

Can I lower my tyrosine levels on my own?

This is not something to attempt without medical guidance. Tyrosine is essential for making proteins and important brain chemicals, so cutting it carelessly could cause harm. The study suggests that lowering tyrosine might help only in people who already have high levels, which requires a blood test to identify. If you are curious about your own levels, the right step is a conversation with your doctor, not a do-it-yourself diet change.

Bottom Line

In a large study of more than 270,000 adults, higher blood tyrosine was tied to a shorter lifespan, and the link held up under a genetic method designed to test cause and effect. The effect was strongest in men, who lost close to a year of life, while the signal in women was weak and uncertain. Phenylalanine showed no independent role. This does not mean you should fear protein, but it does open a promising path: for people with truly high tyrosine, lowering it may one day prove to extend life.

Read the full study