A study has raised fresh questions about tyrosine, an amino acid used in nutrient supplements for mental alertness. Higher levels were linked to a shorter lifespan in men, although the research did not test supplements themselves.

Researchers from the University of Hong Kong and the University of Georgia analysed health and genetic data from UK Biobank participants. Their study examined circulating tyrosine and phenylalanine in relation to mortality.

Published in Aging on 3 October 2025, the research combined cohort analysis with Mendelian randomisation. The genetic analysis used variants as proxies for naturally occurring amino-acid levels.

After controlling for phenylalanine, the MR-Egger analysis estimated that men with higher genetically predicted tyrosine levels had 0.91 fewer years of life per standard-deviation increase. The 95 per cent confidence interval ranged from 0.21 to 1.60 fewer years.

The main analysis found no statistically significant association between tyrosine and lifespan in women. Phenylalanine was also not independently associated with lifespan in either sex after tyrosine was taken into account.

What Tyrosine Does

Tyrosine is a non-essential amino acid that the body can make from phenylalanine. Both are building blocks for proteins, while tyrosine is also a precursor to dopamine, noradrenaline and adrenaline.

The findings may therefore be relevant to people taking tyrosine products for mental performance. However, the study measured circulating levels and genetic proxies rather than testing whether taking a tyrosine supplement affects longevity.

That distinction matters because Mendelian randomisation assesses endogenous exposures. The authors noted that this differs from studying nutrient supplementation, so the findings cannot establish that taking a tyrosine supplement shortens life.

Why Higher Levels Might Matter

The researchers do not yet know why higher tyrosine might be associated with shorter lifespan. The paper discusses insulin resistance as one possible pathway and also considers neurotransmitter and hormonal pathways.

These mechanisms remain speculative. The authors said further investigation is needed and suggested that reducing tyrosine in people with elevated concentrations might potentially contribute to longer lifespan.

The study also has limitations, including a single measurement of circulating amino acids and possible residual confounding. These factors mean the findings should not be interpreted as proof that tyrosine itself causes earlier death.

The Bigger Supplement Question

The findings come as interest in brain-health supplements remains high. Harvard Health reported in February 2026 that about one in four adults over 50 take at least one supplement to improve brain health, memory or focus.

Dr Pieter Cohen of Harvard Medical School said there is no evidence that an ingredient in supplements can improve brain health. His comments highlight the wider uncertainty surrounding products promoted for memory, focus and mental performance.

A separate 42-day randomised, double-blind trial examined Neuriva, which contains whole coffee cherry extract and phosphatidylserine. The trial reported improvements in some cognitive measures, although several authors were Reckitt employees.

What the Study Really Shows

The study raises a legitimate question about whether higher tyrosine levels could have implications for longevity, particularly in men. It does not show that brain-health supplements containing tyrosine cut life short.

Nor does it establish that people should avoid tyrosine-rich foods or protein. The evidence concerns circulating tyrosine and genetic proxies, not the effect of taking a supplement.

For supplement users, the key message is therefore one of uncertainty. The study provides a reason for further research, not proof that taking tyrosine will shorten your life.

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