A glass of wine each evening is enough to increase your risk of developing cancer, women are being warned.
Consuming just one drink a day causes an extra 7,000 cancer cases - mostly breast cancer - in UK women each year, Cancer Research UK scientists say.
The risk goes up the more you drink, whether spirits, wine or beer, the data on over a million women suggests.
Overall, alcohol is to blame for about 13% of breast, liver, rectum, mouth and throat cancers, the researchers say.
They estimate that about 5,000 cases of breast cancer in the UK - 11% of the 45,000 cases diagnosed each year - can be attributed to women's consumption of alcohol.
The study looked specifically at women who consumed low to moderate levels of alcohol - defined as three drinks a day or fewer.
Over the seven years of the study, published in the Journal of the National Cancer Institute, a quarter of the 1.3 million women reported drinking no alcohol.
About 5% of all cancers in the UK are due to drinking something in the order of one alcoholic drink a day
Lead author Dr Naomi Allen
Of those who did drink, virtually all consumed fewer than 21 drinks per week, and an average of 10g of alcohol per day, which is equivalent to just over one unit of alcohol found in half a pint of lager, a 125ml glass of wine or a single measure of spirits.
Nearly 70,000 of the middle-aged women developed cancer and a pattern emerged with alcohol consumption.
One too many?
Consuming one drink a day increased the risk of all types of cancer by 6% in women up to the age of 75.
The rates for individual cancers varied, with one drink a day causing a 12% rise in the risk of breast cancer, a 10% rise in rectal cancer, a 22% rise in gullet cancer, a 29% rise in mouth cancer and a 44% rise in throat cancer.
On a population scale, this would mean 15 extra cases of these cancers diagnosed for every 1,000 women - comprising 11 breast, one mouth, one rectal cancer and 0.7 each for cancers of the gullet, throat and liver.
The government says no amount of alcohol is fully safe, but recommends women should drink no more than two to three units per day on a regular basis to have a lower risk of any harm to health.
For men the recommended limit is no more than three to four units per day.
Mixed messages
Lead author Dr Naomi Allen from the University of Oxford said her work would help the government assess whether the limits should be changed, although the study did not look at men.
"The findings of this report show quite strongly that even low levels of drinking that were regarded to be safe do increase cancer risk.
"About 5% of all cancers in the UK are due to drinking something in the order of one alcoholic drink a day."
She said there was confusion about how much people should drink. Research has shown a daily tipple can be good for the heart. And factors other than alcohol pose a bigger risk for certain cancers.
"It is up to individual people to make their own decision. All of us to some extent have to weigh up the risks and take some responsibility for our health," said Dr Allen.
Around 80% of breast cancer cases are diagnosed in women aged over 50, so limiting how much you drink is one step you can take to try to reduce your risk of developing the disease
Dr Sarah Cant,
Breakthrough Breast Cancer
A Department of Health spokesman said: "We keep our guidance on sensible drinking under review. We currently advise on a lower risk drinking limit and that drinking above this level could be harmful.
"There is no completely safe level of drinking but this lower level reflects the known risks including breast cancer, which is partly why there is a lower drinking limit for women.
"We look forward to examining this research in more detail."
Dr Sarah Cant of Breakthrough Breast Cancer said: "We already know that drinking alcohol can increase your risk of breast cancer.
"This study suggests that for women over 50 even drinking moderate amounts of any type of alcohol can have many health consequences, including a greater chance of developing breast cancer.
"Around 80% of breast cancer cases are diagnosed in women aged over 50, so limiting how much you drink is one step you can take to try to reduce your risk of developing the disease."
Breast cancer is now the most common cancer in the UK. Each year almost 45,000 women are diagnosed with breast cancer. A woman's lifetime risk for breast cancer in the UK is one in nine.
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