L-tyrosine is an amino acid that we include in our Endurolytes and HEED products to help support thyroid and adrenal function. Blood plasma deficiency of this amino acid during endurance exercise will lower thyroid and adrenal production, which hinders metabolism, leading to fatigue. According to Dr. Bill Misner, "Symptoms of l-tyrosine depletion first appear as depression, later anger, then despondency that degenerates into total despair." If you've experienced these symptoms during a training session or race, chances are it's due to low thyroid and adrenal production. You can easily avoid this problem by supplementing l-tyrosine via HEED and/or any of the Endurolytes products. Tyrosine is also purported to help increase alertness, a definitely plus during ultra distance workouts and races.
