According to Science Daily:
Drinking just one glass of wine or other alcoholic drink a day increases breast cancer risk, finds a major new report by the American Institute for Cancer Research (AICR) and the World Cancer Research Fund (WCRF).The report also revealed, for the first time, that vigorous exercise such as running or fast bicycling decreases the risk of both pre- and post-menopausal breast cancers. Strong evidence confirmed an earlier finding that moderate exercise decreases the risk of post-menopausal breast cancer, the most common type of breast cancer.