Overall, the risk of cancer increased as alcohol consumption increased. The type of alcohol consumed appeared to make no difference.
Women who drank and also smoked faced increased risk of cancers of the oral cavity and pharynx, esophagus, and larynx (voice box), the researchers found.
The study suggests "that in developed countries, where women typically consume low-moderate amounts of alcohol, we estimate that for every additional drink regularly consumed each day, there would be about 15 extra cases of cancers of the breast, liver, rectum and mouth and throat diagnosed for every 1,000 women up to the age of 75," Allen said. "Most of this excess risk is due to breast cancer."
Susan M. Gapstur, vice president of epidemiology at the American Cancer Society, said the findings confirm and expand on those from previous studies in men and in smaller cohorts of women.
But several questions remain unanswered, she said. "For example, researchers remain concerned about the pattern of consumption," Gapstur said. "It is unclear, for example, whether someone who drinks several glasses of wine on one day during the week has the same risk as someone who drinks one glass of wine per day with a meal. In addition, the effects of quitting or reducing drinking on cancer risk are also unclear."
The American Cancer Society currently recommends limiting intake to one drink a day for women and two drinks a day for men, Gapstur said.
On the other hand, numerous studies have suggested that alcohol, especially red wine, might help deter heart disease -- complicating decisions around drinking and health.
"If you do not drink, there is no reason to start drinking," Gapstur reasoned. "However, in light of the findings from the Million Women Study, women who are concerned about their cancer risk versus their risk of cardiovascular disease might want to discuss the potential
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