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The relationship between alcohol and breast cancer has been a subject of significant research. It has long been considered a risk factor for breast cancer in women. The International Agency for Research on Cancer has declared that there is sufficient scientific evidence to classify alcoholic beverages a Group 1 carcinogen that causes breast cancer in women.〔''Alcohol consumption and ethyl carbamate'' International Agency for Research on Cancer Working Group on the Evaluation of Carcinogenic Risks to Humans (2007: Lyon, France) ISBN 9789283212966〕 Group 1 carcinogens are the substances with the clearest scientific evidence that they cause cancer, such as smoking tobacco. A woman drinking an average of two units of alcohol per day has 8% higher risk of developing breast cancer than a woman who drinks an average of one unit of alcohol per day.〔 A study of more than 1,280,000 middle-aged British women concluded that for every additional drink regularly consumed per day, the incidence of breast cancer increases by 1.1%. Approximately 6% (between 3.2% and 8.8%) of breast cancers reported in the UK each year could be prevented if drinking was reduced to a very low level (i.e. less than 1 unit/week).〔''(Non-Technical Summary )'' Committee on Carcinogenicity of Chemicals in Food Consumer Products and the Environment (COC)〕 Among women, breast cancer comprises 60% of alcohol-attributable cancers. A study of 17,647 nurses found that high drinking levels more than doubled risk of breast cancer with 2% increase risk for each additional drink per week consumed. Binge drinking of 4–5 drinks increases the risk by 55%. ==Mechanism== The mechanisms of increased breast cancer risk by alcohol may be: *Increased estrogen and androgen levels *Enhanced mammary gland susceptibility to carcinogenesis〔 *Increased mammary DNA damage〔 *Greater metastatic potential of breast cancer cells〔 Their magnitude likely depends on the amount of alcohol consumed.〔 Susceptibility to the breast cancer risk of alcohol may also be increased by other dietary factors, (e.g. folate deficiency), lifestyle habits (including use of hormone replacement therapy), or biological characteristics (e.g. as hormone receptor expression in tumor cells).〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Alcohol and breast cancer」の詳細全文を読む スポンサード リンク
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