The list of cancers associated with smoking is a long one: lung, esophagus, throat and larynx, as well as

kidney, bladder, pancreas and stomach. Now add breast cancer to the toll.

Until now, studies had not been able to definitively link smoking to breast cancer because of tobacco's

double-edged effect. While its carcinogens can trigger tumors to grow in breast tissue, its ability to block

estrogen, a hormone that promotes breast cancer, may actually work to suppress malignancies. The

latest research clarifies the risk, finding that premenopausal women who smoked had a higher risk of

breast cancer than women who didn't, but after menopause, women who puffed cigarettes were slightly

less likely to develop the disease than nonsmokers. The theory is that postmenopausal women have low

levels of circulating estrogen and may benefit further from tobacco's antiestrogenic effects.

Overall, the added breast-cancer risk from regular smoking at any age was 6%, but that figure shot up for

heavy smokers. Women who lit up before age 18 and smoked for three decades or longer had a 25%

greater chance of the disease than nonsmokers.

Given the small window of time during which smoking may protect against cancer in the breast, it's a

good idea to kick the habit now.