High tyrosine levels tied to shorter male lifespan in large study
A UK Biobank analysis linked higher blood tyrosine to reduced life expectancy in men, though supplements were not directly tested.
By Tom Brennan · Health & Medicine Correspondent
3 min read
Researchers analyzing data from more than 270,000 people found that men with higher blood levels of tyrosine had shorter estimated lifespans, according to Impact Journals LLC and a study published in Aging. The finding draws attention because tyrosine is an amino acid found in many protein-rich foods and sold in supplements promoted for focus, alertness and cognitive performance.
The research was conducted by Jie V. Zhao, Yitang Sun, Junmeng Zhang and Kaixiong Ye of the University of Hong Kong and the University of Georgia, according to Impact Journals. The team examined tyrosine and phenylalanine, two amino acids involved in metabolism and brain activity.
What the researchers studied
Impact Journals said the study used health and genetic information from UK Biobank, a large long-term health database. The researchers looked at observed links between amino acid levels and mortality, then used Mendelian randomization, a genetic analysis method used to test whether an association may reflect a causal relationship.
Tyrosine is used by the body to make neurotransmitters including dopamine, norepinephrine and epinephrine, according to Impact Journals. Those chemical messengers are involved in mood, attention, motivation, memory and the stress response.
Phenylalanine and tyrosine occur naturally in foods such as meat, fish, eggs and dairy products, Impact Journals said. The same amino acids are also available in dietary supplements marketed for energy and mental performance.
Tyrosine showed the stronger link
According to the study summary, both phenylalanine and tyrosine initially appeared to be associated with higher mortality risk. After the researchers adjusted for additional factors and ran more detailed analyses, tyrosine remained the amino acid consistently tied to lifespan.
The association appeared in men but not women, Impact Journals said. Based on genetic analyses, the researchers estimated that higher tyrosine levels could reduce male life expectancy by close to one year.
The study reported no significant link between tyrosine levels and lifespan among female participants, according to Impact Journals. The researchers also noted that men generally have higher tyrosine levels than women, which they said may help account for part of the long-observed difference in average lifespan between men and women.
Phenylalanine did not remain associated with lifespan in either sex after the researchers accounted for tyrosine, according to the study.
Open questions for diet and supplements
The researchers have not established exactly how tyrosine might affect aging, Impact Journals said. Possible mechanisms include insulin resistance, which is linked to type 2 diabetes, cardiovascular disease and other metabolic problems, as well as changes in neurotransmitter systems involved in stress.
Hormone-related pathways may also be involved, according to the researchers. Impact Journals said those pathways can differ between men and women, which may help explain why the association was seen only in men.
The study did not test tyrosine supplements directly and did not prove that taking supplemental tyrosine shortens lifespan, according to Impact Journals. It examined blood levels of the amino acid and their relationship with longevity.
The researchers said dietary approaches such as reducing overall protein intake may lower tyrosine levels, according to Impact Journals. They said more studies are needed to confirm the findings in other populations, clarify the biology involved and test whether lowering tyrosine can safely support healthier aging.
This story draws on original reporting from ScienceDaily.