Dr. Arthur Klatsky, of the Kaiser Permanente Medical Care Program, in Oakland, Calif., studied the drinking habits of more than 70,000 multi-ethnic women who had supplied personal information during health examinations from 1978 to 1985. By 2004, 2,829 of these women had been diagnosed with breast cancer.

The researchers found that there was no difference in the risk of developing breast cancer among the alcoholic beverages of wine, beer or spirits. However, the researchers found that women who drank between one and two alcoholic drinks per day increased their risk of breast cancer by 10 percent compared with light drinkers who drank less than one drink a day.

The risk of breast cancer increased by 30 percent in women who drank more than three drinks a day, Klatsky said at the European Cancer Conference in Barcelona, Spain.

"A 30 percent increased risk is not trivial," Klatsky said. "Incidentally, in this same study we have found that smoking a pack of cigarettes or more per day is related to a similar -- 30 percent -- increased risk of breast cancer."