The Popular Focus Supplement That May Cost Men a Year of Life

Key takeaways

• A study of more than 270,000 people found that higher blood levels of tyrosine, an amino acid found in protein-rich foods and sold as a focus-boosting supplement, were linked to shorter lifespan in men specifically.

• Using genetic analysis, researchers estimated the effect could shorten male lifespan by nearly a year, while no meaningful effect showed up in women.

• The takeaway: this doesn't mean tyrosine supplements are dangerous, but it does raise a useful question about whether more of a "good" compound is always better, and whether the answer depends on who you are.

A closer look at two everyday amino acids

Researchers set out to test whether phenylalanine and tyrosine—two amino acids central to metabolism and brain chemistry—track with how long people live. Using data from more than 270,000 participants in the UK Biobank, they looked at blood concentrations of both compounds alongside mortality outcomes and predicted lifespan.

At first glance, higher levels of both amino acids appeared linked to a greater mortality risk. But once the researchers dug deeper using genetic methods, one amino acid consistently stood out: tyrosine.

Why the sex difference matters

The team used a technique called Mendelian randomization, which leans on naturally occurring genetic variation to get closer to cause-and-effect rather than just association. This approach suggested that elevated tyrosine may have a real, potentially causal relationship with reduced life expectancy in men—on the order of nearly a year. Notably, phenylalanine's link disappeared entirely once tyrosine was accounted for, while women showed no significant tyrosine effect at all.

Men in the study also tended to have naturally higher tyrosine levels than women, which raises an intriguing possibility: differences in this single amino acid could be one small piece of the puzzle behind why average lifespan differs between the sexes. The researchers are careful to note this doesn't prove tyrosine drives that gap—it's one thread among many still being untangled.

What might be going on biologically

Nobody knows for certain yet why tyrosine would behave this way, but researchers have a couple of working ideas. One involves insulin sensitivity—tyrosine metabolism may interact with how efficiently cells respond to insulin, a pathway closely tied to healthy aging. Another involves neurotransmitter production: the body converts tyrosine into dopamine and related stress-response chemicals, and these signaling pathways can behave differently in men versus women. Both explanations remain hypotheses that need further testing.

A longevity lens: more nuance, not more alarm

This is a good example of why "more of a beneficial nutrient" isn't automatically better from a longevity standpoint. Tyrosine is a normal, necessary amino acid, and this study didn't test supplements directly—it looked at natural blood levels, not the effects of taking a tyrosine supplement. So there's no evidence here that occasional supplement use is harmful.

What it does suggest is that individual biology, including things like sex, may shape how a compound affects long-term health outcomes. That's a theme showing up more and more in longevity research: the same input doesn't always produce the same output across different people, and blanket recommendations may eventually give way to more personalized ones.

The takeaway

This study isn't a reason to panic about protein intake or toss out a supplement regimen. It's a reminder that even well-studied, everyday compounds can have effects that differ by sex and depend on levels that are hard to judge from the outside. For now, the most useful takeaway may simply be curiosity: as researchers continue to untangle how amino acids like tyrosine interact with aging, the picture is likely to get more personalized, not more one-size-fits-all.

References:

Zhao, J.V., Sun, Y., Zhang, J., Ye, K. The role of phenylalanine and tyrosine in longevity: a cohort and Mendelian randomization study. Aging, 2025; 17(10): 2500. DOI: 10.18632/aging.206326.