The main health-promoting substances in tea are polyphenols, in particular catechins and epicatechins. Lab and animal studies say these molecules have anti-inflammatory and antioxidant properties. Harvard-led studies of large groups of people over time have found that tea or coffee drinkers are at lower risk for diabetes and possibly cardiovascular disease. Coffee also contains polyphenols . Tea, especially green tea, is often said to be good for your health.Tea contains substances linked to a lower risk for heart disease, cancer, and diabetes.