In this study led by Jie V. Zhao, Yitang Sun, Junmeng Zhang, and Kaixiong Ye from the University of Hong Kong and the University of Georgia, researchers investigated whether two amino acids, phenylalanine and tyrosine, affect how long people live (lifespan). The results suggest that higher levels of tyrosine are linked to shorter life expectancy in men, pointing to potential sex-specific approaches to promoting longevity.