A widely used supplement ingredient, often promoted for enhancing cognitive function and focus, may be associated with a shorter lifespan in men, according to recent research. While it could sharpen the mind, the nutrient might have an unexpected impact on longevity, the study suggests.
Scientists from the University of Hong Kong and the University of Georgia analyzed health and genetic data from over 270,000 individuals in the UK Biobank. Their investigation focused on phenylalanine and tyrosine, two amino acids that play crucial roles in the body.
Tyrosine is an essential building block for proteins and is also involved in the production of neurotransmitters like dopamine and adrenaline, which are critical for mood, focus, and stress response. Phenylalanine is converted into tyrosine in the body. Both amino acids are naturally present in protein-rich foods and are common components of dietary supplements.
To explore the potential link between these nutrients and longevity, researchers examined participants' blood levels of phenylalanine and tyrosine and compared them with mortality rates and predicted lifespans. They also employed Mendelian randomization, a genetic technique that utilizes natural genetic variations to infer causal relationships.
The study's findings indicated that men with higher concentrations of tyrosine in their blood appeared to have shorter lifespans, with elevated levels correlating to a reduction of nearly one year in their expected life. In contrast, women did not exhibit the same association. Phenylalanine showed no significant link to lifespan in either sex after accounting for tyrosine levels.
While the exact reasons for the observed association in men are not yet fully understood, researchers have proposed several hypotheses. One theory centers on insulin resistance, a condition where the body's cells become less responsive to insulin, a hormone that regulates blood sugar. Tyrosine plays a role in the signaling pathway that helps insulin facilitate sugar uptake by cells. Excessive circulating tyrosine could potentially disrupt this process, and insulin resistance is linked to various age-related health issues that can affect longevity, including cardiovascular disease and Type 2 diabetes.
Another potential factor involves the brain chemicals tyrosine helps produce, which are involved in mood and stress regulation. Differences in these chemical pathways between sexes might explain why the longevity link was observed only in men. The researchers also posited that tyrosine could contribute to the well-documented difference in average lifespan between men and women, though they emphasized that their study does not definitively prove the amino acid is the cause.
The study authors advised that individuals with unusually high blood levels of tyrosine might consider dietary adjustments to lower these concentrations. Foods rich in tyrosine include chicken, turkey, beef, lamb, fish, hard cheeses, eggs, sesame seeds, soybeans, and nuts.
However, the researchers stressed that these findings do not warrant discarding all supplements containing tyrosine. The study did not directly test the safety of commercial supplements, and there is no direct evidence that taking them will shorten life. Previous research has also suggested that tyrosine can offer benefits for mental focus, memory improvement, and cognitive function under stress. The study's implications are primarily for individuals with naturally high tyrosine levels, who might benefit from assessing their dietary intake.