Amino acids are tiny parts of proteins that help our bodies grow and heal. Two of these, phenylalanine and tyrosine, are found in meat, fish, eggs, dairy and many diet pills.
What does tyrosine do?
Tyrosine helps the brain make important chemicals called neurotransmitters. These messengers affect mood, focus, memory and how we react to stress.
Big study looks at blood levels
Researchers studied more than 270,000 people from the UK Biobank. They checked the participants' blood for phenylalanine and tyrosine and then followed them to see who lived longer.
They used two methods: a simple look‑at‑the‑data comparison and a genetic technique called Mendelian randomization, which helps tell if one thing might cause another.
Tyrosine stood out
At first, both amino acids seemed to be linked with a higher chance of death. After adjusting the numbers, only tyrosine kept a clear connection.
Men with higher tyrosine in their blood lived about one year less than men with lower levels. The same pattern was not seen in women.
Why might tyrosine affect aging?
Scientists are not sure yet, but a few ideas exist. Too much tyrosine could make the body less sensitive to insulin, which is linked to diabetes and heart disease.
It might also change how stress‑related chemicals are made, or affect hormone pathways that work differently in men and women.
What does this mean for supplements?
Tyrosine is sold as a supplement that promises sharper focus and better mood during stressful times. The study did not test these pills directly, only the natural blood levels.
So we cannot say the pills are dangerous, but the results suggest that having too much tyrosine over many years could be worth checking.
Next steps
More research is needed. Scientists want to see if other groups show the same link, and whether diet or lifestyle changes can safely lower tyrosine and improve healthy aging.
For now, the finding reminds us that a nutrient good for brain chemistry might also play a surprising role in how long we live.