Every year, millions of people take amino acid supplements in hopes of gaining a mental edge. The pitch is consistent. These compounds supply brain chemicals associated with focus, motivation, and stress resistance. Short-term science works, especially when it comes to one amino acid, tyrosine.
One question that has not been previously measured in humans is whether there are any costs to keeping tyrosine levels elevated for decades. A large-scale new analysis asked that question and found different answers for men and women.
Tyrosine in the spotlight
Dr. Jie V. Zhao, an epidemiologist at the University of Hong Kong (HKU), led a team that analyzed the health and genetic data of more than 272,000 people registered in the UK Biobank, a large health research database in the United Kingdom.
The research team set out to test whether two related amino acids, tyrosine and its chemical precursor phenylalanine, had a measurable link to human longevity. Both occur naturally in protein-rich foods such as meat, eggs, dairy products, and soy.
To enhance their analysis, the team also used a genetic approach. It looks at genetic DNA differences to infer cause and effect, rather than relying on blood measurements that can be distorted by disease or other factors.
discoveries for men
Initially, both amino acids appeared to be associated with an increased risk of early death. However, once the research team considered the overlap between the two, phenylalanine’s relevance faded. Tyrosine was not.
For men, genetically high tyrosine levels shorten lifespan by nearly a year (on average, about 0.9 years). Women showed no clear association.
This gender difference turned out to be one of the study’s most striking findings. Although the participants shared a nearly similar diet and environment, the biological influences were not the same.
Why tyrosine affects aging
Although the exact mechanism is not clear, two possibilities stand out. One is insulin resistance. A condition in which cells no longer respond properly to insulin, increasing the risk of diabetes and other age-related diseases.
Previous studies have linked increased blood tyrosine to an increased likelihood of developing insulin resistance, which may help explain why increased blood tyrosine levels accelerate certain aspects of aging.
A 2022 study found that this link was especially pronounced in people who carried excess weight.
Tyrosine is also the starting point for dopamine, adrenaline, and noradrenaline, chemicals that regulate how the body deals with stress.
These chemicals interact with sex hormones, which may explain, in part, why the association with shorter lifespans is more evident in men than in women.
Restriction of animal tyrosine intake
Scientists have long suspected that specific amino acids, rather than whole proteins, may promote the longevity effects seen with low-protein diets. Animal experiments have begun to confirm this.
In experiments with fruit flies, restricting tyrosine intake extended the animals’ lifespans, possibly by suppressing biological processes associated with aging, according to research published in 2024.
Researchers found a similar pattern in rodents. When the researchers reduced the rats’ overall protein intake, tyrosine levels in their tissues decreased and the rats lived longer.
Until this study, no one had tested that pattern in humans at this scale. The results matched what animal studies predicted.
why men die early
In almost all countries, men die younger than women. In the U.S., the gap reached nearly six years during the coronavirus pandemic, making it the largest gap since 1996, according to the study.
There is no single explanation for this. However, young men naturally retain more circulating tyrosine than young women.
The new findings suggest that this gap in baseline levels may be a metabolic part of why men consistently die earlier.
data is retained
Zhao’s team performed the genetic analysis in multiple ways and applied various statistical techniques to ensure that the results were not skewed by external factors. The direction of the association applies to all of them. The results were consistent.
The apparent relationship between phenylalanine and longevity primarily reflects its chemical relationship with tyrosine.
When tyrosine was taken into account in the analysis, phenylalanine’s independent effect on longevity disappeared, but its independent association with heart disease and cancer risk remained.
What does this change?
Zhao notes that the study did not directly test supplements. Blood tyrosine levels reflect genetics, diet, and metabolism. A single measurement recorded years before death cannot tell the whole story.
This finding contains an implicit warning for those who use tyrosine supplements long-term.
“Our study did not support a longevity benefit of long-term use of tyrosine,” Zhao said.
That doesn’t mean you should eliminate protein-rich foods. Tyrosine is essential for normal function. However, this study suggests that researchers can now investigate whether moderate protein restriction or a similar dietary approach may improve healthy aging in men, a question now supported by human genetic evidence.
This study, for the first time on this scale in humans, demonstrates that tyrosine is not just a brain chemical precursor that increases performance. For men, chronically high levels appear to be directly related to longevity.
This research aging.
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