THURSDAY, Sept. 27 (HealthDay News) -- Three or more drinks a day boosts a woman's risk for breast cancer by 30 percent. And it doesn't seem to matter which form of alcohol -- wine, beer, or spirits -- is consumed, researchers report.
"The majority of previous studies have found an association between alcohol and elevated breast cancer risk," said lead researcher Dr. Yan Li, an oncologist at Kaiser Permanente in Oakland, Calif.
What hasn't been as clear, she said, is how much alcohol raises the risk and whether one type of alcohol boosts that risk more than another.
Li tackled those questions with Dr. Arthur Klatsky, an investigator at the Kaiser Permanente Division of Research in Oakland and a long-time researcher on the health benefits and risks of alcoholic beverages. Klatsky is due to present the team's findings Sept. 27 at the European Cancer Conference in Barcelona, Spain.
The researchers first evaluated the drinking habits of more than 70,000 women, all members of the Kaiser Permanente HMO. The women had undergone health exams during the years 1978 to 1985. By 2004, more than 2,800 women had experienced a breast cancer diagnosis.
Comparing the women's drinking habits to the incidence of breast cancer, the team found that women who drank between one and two alcoholic drinks a day increased their risk of breast cancer by 10 percent compared to light drinkers -- defined as those who drank less than one drink a day.
That risk rose as drinking rates increased. "The risk of breast cancer increased by 30 percent in women who drank three or more drinks per day" compared to light drinkers, Li said.
"What we are saying is, whatever your baseline risk is of getting breast cancer, by consuming alcohol you have this increment," Li said.
The risk of breast cancer in individual women varies greatly, Li said, depending on their family history and whether they are genetically predisposed due to mutations of the so-called breast cancer genes, BRCA-1 and BRCA-2.
In the general population, the lifetime risk of getting breast cancer is one in eight women, Li said. Based on the study findings, however, "if you drink three or more drinks a day, that risk -- rather than one in eight -- will be one in six," she said.
The increase in risk was similar no matter which type of beverage was typically consumed. "It makes no difference whether women drink wine, beer or liquor in terms of their risk of breast cancer," Li said. "It's the alcohol itself. And it's the quantity consumed that increases breast cancer risk."
The researchers didn't find any difference in risk between red and white wine, although some previous research has found red wine more heart-protective than white. That cardiovascular benefit has been linked to the presence of antioxidant flavonoids in red wine, especially one flavonoid called resveratrol.
Another expert familiar with the new study said the research adds some valuable information to what is known about breast cancer risk. Especially valuable -- because it is new -- is the information about all types of alcohol seeming to raise risk equally, said Coral Lamartiniere, a professor of pharmacology and toxicology at the University of Alabama at Birmingham.
He has researched resveratrol, which has shown both antioxidant and anticancer properties. In a study published in August in the journal Carcinogenesis, Lamartiniere found that animals fed resveratrol had an 87 percent reduced risk of getting prostate tumors.