A study has linked higher blood levels of tyrosine — an amino acid sold as a “brain” supplement for focus and alertness — to a shorter lifespan in men. But the researchers are emphatic about what it does not show.
Using data from over 270,000 UK Biobank participants, an observational analysis plus a Mendelian randomization study (a genetics-based method that can hint at causality) found that higher tyrosine levels were associated with reduced life expectancy in men — by nearly a year — with no effect seen in women. The work, from the University of Hong Kong and University of Georgia, appeared in Aging-US.
The crucial caveats
Here’s what matters most: the researchers did not test tyrosine supplements at all. As they put it, the results “do not show that taking a tyrosine supplement shortens lifespan.” They looked at naturally occurring blood levels, not supplementation. The genetic analysis suggested a possibly causal link, but the proposed mechanisms — insulin resistance, or tyrosine’s role in stress-response neurotransmitters — remain untested hypotheses.
Why it matters
The supplement industry is large and lightly regulated, and “more of a good amino acid” isn’t always better. The honest takeaway is modest: this is an early signal worth studying, not evidence that a tyrosine supplement is harmful. It’s a reminder to be cautious about high-dose supplements marketed on thin evidence — and to bring questions to a clinician. This article summarizes research and is not medical advice.