Common Brain Supplement May Cut Men's Lifespan, Study Finds

When we talk about “brain‑boosting” pills, tyrosine often gets a nod for its role in making dopamine and other neurotransmitters. Yet a new study of more than 270,000 people hints that this popular amino acid might have a darker side—at least for men.

Researchers from the University of Hong Kong and the University of Georgia dug into the UK Biobank, a treasure‑trove of health and genetic data. They focused on two amino acids, phenylalanine and tyrosine, asking whether the amounts floating around in our blood say anything about how long we’ll live.

At first glance, both seemed to raise the risk of death. But when the team applied Mendelian randomization—a technique that uses genetic variants as natural experiments—the picture sharpened. Tyrosine, not phenylalanine, kept popping up as the culprit.

For men, higher circulating tyrosine translated to an estimated loss of almost a year of life. Women, on the other hand, showed no meaningful change. The researchers also noted that, on average, men have slightly higher tyrosine levels than women, a fact that could be one piece of the puzzle explaining why men tend to live shorter lives.

Why would tyrosine matter? One theory points to insulin resistance, a condition that climbs with age and is linked to many chronic diseases. Another possibility is that tyrosine‑derived neurotransmitters influence stress pathways differently in men and women. Both ideas are still speculative; more work is needed.

It’s worth stressing that the study didn’t test tyrosine supplements directly. The investigators measured the amino acid already present in participants’ blood, not what they might have taken in a pill. Still, the findings raise a cautionary flag for anyone loading up on over‑the‑counter tyrosine hoping for a mental edge.

Bottom line: while tyrosine is essential for normal brain function, consistently high levels may be linked to a modest reduction in male lifespan. Until we understand the mechanisms better, moderation—and a balanced diet—remain the safest bet.