Lipton Natural Energy Tea is a black tea that naturally contains caffeine and L-theanine, an amino acid. The teas contains 75 mg of caffeine and 20 mg  L-theanine.

Kelly Sloan, Bite of the Best Intern:  The Lipton Natural Energy tea contains L-theanine, a naturally occurring amino acid found in tea that transmits brain nerve impulses. I enjoyed both the flavor and stimulating effect of the tea.