“Black tea is oxidized most extensively; hence its black color,” says Dr. Brill. “Most of the benefits come from powerful plant chemicals knwn as polyphenols, as well as flavonoids.” Suzanne Steinbaum, DO, the director of Women’s Heart Health at Lenox Hill Hospital in New York City, regularly advises her coffee-drinking patients to consider switching to black tea because it has roughly half the amount of caffeine as a same-sized cup of coffee. And results of a clinical trial published in the May 2012 Preventive Medicine journal indicated that people who drank three cups of black tea per day had, on average, 36 percent lower triglyceride levels and a 17 percent improvement in their cholesterol profiles.
“All black teas are caffeinated, which is not great if you have high blood pressure or a fast heart rate — it can make things worse,” warns Dr. Steinbaum. For black teas, you may expect anywhere from 14 to 70 mg of caffeine, notes the Mayo Clinic.
“Stimulants can trigger heart arrhythmias in some patients,” says John Day, MD, cardiologist and heart rhythm specialist at the Intermountain Heart Institute in Murray, Utah. “If any teas give you palpitations or a rapid heartbeat, you should stop drinking them and let your doctor know.” And use caution if you’re taking Coumadin (warfarin), a commonly prescribed blood thinner, as black tea may decrease blood clotting and increase your chances of bruising and bleeding.