Research at the Mayo Clinic shows that a component in green tea helps kill cells of the nation's most common form of leukemia.

The scientists say the green tea component -- EGCG -- helps kill the cancer cells by cutting off the communication signals they need to survive.

The cells used in the study were from patients with B-cell chronic lymphocytic leukemia, or CLL. It's most often diagnosed in patients in their mid-to-late 60s -- and currently, there is no cure. The Leukemia & Lymphoma Society says symptoms usually develop gradually. Patients tire more easily and may feel short of breath when physically active. They may lose weight. They may experience frequent infections of the skin, lungs, kidneys or other sites.

The findings, reported in an early electronic article in the journal Blood, show green tea's EGCG killed leukemia cells in eight of ten patient samples tested.

Researchers say the green tea results are an excellent start in an effort to find agents that will kill cancer cells and are nontoxic to the patient.

The Early Show medical correspondent Dr. Emily Senay notes there is still a little debate as to how many cups of tea a person should drink to achieve benefits.

“Somewhere between four and ten cups of green tea a day,” she says, “Seems like a lot but a lot of people in the cultures, which drink high amounts of green tea, which by the way, have low amounts of cancer, sip this throughout the day.”

As for the drink’s caffeine content, she notes green tea has about half as the one in coffee. And if you are sensitive to caffeine you can go for decaf.

While the research found drinking tea is beneficial, it is not clear what the benefits of other products that contain green tea such as facial cleansers or toothpaste may be.