Every year, millions of people take amino acid supplements expecting to gain a mental edge. The pitch is consistent: these compounds feed the brain chemicals tied to focus, motivation, and stress tolerance. For one amino acid in particular – tyrosine – the short-term science holds up.
What no study had measured in humans until now is whether keeping tyrosine elevated over decades carries any cost. A large new analysis asked that question – and found a different answer for men than for women.
Tyrosine in the spotlight
Dr. Jie V. Zhao, an epidemiologist at the University of Hong Kong (HKU), led a team that analyzed health and genetic data from more than 272,000 people enrolled in the UK Biobank, a large British health research database.
The team set out to test whether two related amino acids – tyrosine and its chemical precursor, phenylalanine – had any measurable connection to how long people live. Both are found naturally in protein-rich foods like meat, eggs, dairy, and soy.
To sharpen the analysis, the team also used a genetic approach – one that looks at inherited DNA differences to estimate cause and effect rather than relying on blood measurements that illness or other factors can distort.
The finding for men
At first, both amino acids appeared linked to a higher risk of early death. But when the team accounted for the overlap between the two, phenylalanine’s association faded. Tyrosine’s did not.
In men, genetically higher tyrosine levels were associated with losing close to a year off their lifespan – about 0.9 years on average. Women showed no clear association.
That sex difference turned out to be one of the study’s most striking results. Participants shared broadly similar diets and environments, yet the biological effects were not the same.
Why tyrosine affects aging
The exact mechanism isn’t settled, but two possibilities stand out. One involves insulin resistance – a condition where cells stop responding normally to insulin, raising the risk of diabetes and other age-related diseases.
Prior research linked higher blood tyrosine to a greater chance of developing insulin resistance, which may help explain why elevated levels appear to speed up certain aspects of aging.
A study from 2022 found this connection especially pronounced in people carrying excess weight.
Tyrosine is also the starting point for dopamine, adrenaline, and noradrenaline – the chemicals that regulate how the body handles stress.
Those chemicals interact with sex hormones, which may partly explain why the life-shortening association is clearer in men than in women.
Restricting tyrosine intake in animals
Scientists had suspected for years that specific amino acids, rather than protein broadly, might drive the longevity benefits seen with lower-protein diets. Animal experiments began confirming it.
In fruit fly experiments, restricting tyrosine intake extended how long the animals lived – possibly by dialing down biological processes tied to aging – according to a study published in 2024.
Researchers found a similar pattern in rodents. When researchers cut overall protein intake in rats, tyrosine concentrations in tissue dropped and the animals lived longer.
Until this study, no one had tested that pattern in humans at this scale. The results aligned with what the animal work had predicted.
Why men die sooner
Men die younger than women in nearly every country. In the United States, that gap reached nearly six years during the COVID-19 pandemic, according to a study – the widest margin since 1996.
No single explanation accounts for this. But young men naturally carry higher circulating tyrosine than young women.
That gap in baseline levels, the new findings suggest, may be one metabolic piece of why men consistently die sooner.
The data holds up
Zhao’s team ran the genetic analysis multiple ways, applying different statistical methods to make sure the results weren’t being skewed by outside factors. The direction of the association held across all of them. The findings were consistent.
Phenylalanine’s apparent connection to lifespan largely reflects its chemical relationship to tyrosine.
Once the analysis accounted for tyrosine, phenylalanine’s independent lifespan effect dropped out – though it retained separate associations with heart disease and cancer risk.
What this could change
Zhao is careful to note the study didn’t directly test supplements. Blood tyrosine levels reflect genetics, diet, and metabolism. A single measurement captured years before death can’t tell the whole story.
The findings carry an implicit warning for anyone using tyrosine supplements over the long term.
“Our study did not support the benefit of long-term use of tyrosine on lifespan,” said Zhao.
That isn’t a call to eliminate protein-rich foods – tyrosine is essential for normal function. But it does suggest researchers can now investigate whether moderate protein restriction or similar dietary approaches might improve healthy aging in men, a question now backed by human genetic evidence.
What this study establishes, for the first time in humans at this scale, is that tyrosine isn’t just a brain chemical precursor with a performance upside. In men, chronically high levels appear to connect directly to how long they live.
The study is published in Aging.
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