These substances are good for the human body. The lighter the density of tea the better.
Heavy density accelerates the heartbeat, which is dangerous for heart disease patients.
Don't drink dense tea before going to bed, it might keep you awake. Green tea assists with those suffering constipation. Anaemic patients should minimise tea intake because their medication produces a precipitation with tannic acid found in tea. The precipitation cant be absorbed in the intestine. Don't swallow medicine with tea.