Nature's Harbor L-Tyrosine acts as a mood enhancer, suppresses appetite, and helps reduce body fat. L-Tyrosine is an important amino acid that can help calm anxiety and nervousness. L-Tyrosine is a precursor for the synthesis of the biologically active catecholamines epinephrine, norepinephrine and dopamine, the thyroid hormones thyroxine and triiodothyronine, and the pigment melanin.