Estrogen, alcohol and breast cancer risk.

Estrogen replacement has been used for many years to reverse the hypoestrogenic symptoms of menopause and prevent osteoporosis. Studies have found that estrogen replacement also decreases cardiovascular risk. In addition, social use of alcohol has been found to decrease cardiovascular risk. Therefore, both estrogen replacement therapy and alcohol use have been proposed to have cardiovascular benefits, and are often used in combination. Epidemiologic evidence indicates that estrogen replacement therapy after menopause increases breast cancer risk. Regular alcohol consumption is also associated with increase in risk. However, interactions between the two are poorly understood. In addition, if alcohol alters circulating estrogen levels in estrogen users, this may have implications in terms of altering the risks:benefit ratio of estrogen replacement in an undesirable direction. For example, there are data suggesting that the use of both alcohol and estrogen may increase breast cancer risk more than the use of either one alone. Data support both acute and chronic effects of alcohol in raising circulating estrogen levels in premenopausal women on no hormonal medications. In postmenopausal women studies focusing on acute effects of alcohol on estrogen metabolism indicate that alcohol has a much more pronounced effect in women using estrogen replacement than in those who do not. Studies evaluating chronic effects of alcohol ingestion on circulating estrogens in postmenopausal women are needed.