I want to know which foods (black tea?) can help lower cortisol. i want to gain muscle mass and i read that cortisol has catabolic effects.

Muscle mass: The only safe way to gain muscle mass is to exercise. Black tea will not help at all. Cortisol level has nothing to do with the muscle mass. Anabolic steroids will help you grow facial hair, before you gain muscle mass (if you are a female).

Don`t worry: Your bodies cortisol is produced by a servo mechanism with other glands including the pituitary. You need to do nothing except eat and live healthy. On the other hand if cortisone is given to you in addition to this or if you have a rare disease that produces too much, then it is catabolic and it will take more than diet to offset it. Muscle mass is helped by exercise and protein in a diet.