One glass of wine a day increases risk of breast cancer:

A new study conducted by researchers at Harvard University has found that women who drink just four small glasses of wine a week increase their risk of developing breast cancer by 15 per cent.
In Britain women are recommended to drink no more than 14 units or two small glasses of wine a day with some alcohol free days each week. Experts said the new study confirmed the link between alcohol consumption and breast cancer as it is thought up to one fifth of cases are caused by drinking to excess. There are almost 50,000 cases of breast cancer diagnosed in Britain each year.
Women who drank up to four units a day were 50 per cent more likely to develop breast cancer than those who did not drink at all, it was found. 
Moderate drinking has been found to protect against heart disease and doctors warned women who may consider abstaining from alcohol in light of the findings that they may miss out on these benefits.
The study published in the Journal of the American Medical Association was based on 106,000 nurses in America who were followed up from 1980 until 2008. 


Source  - Telegraph