The type of alcohol did not seem to affect the cancer risk, researchers said. (CBC)

Downing as little as one alcoholic drink a day seems to increase a woman's risk for developing cancer, according to a British study that looked at nearly 1.3 million middle-aged women.

The study in Tuesday's issue of the Journal of the National Cancer Institute suggested the cancer risks of alcohol may outweigh any potential benefits it has on the heart.

"These findings suggest that even low levels of drinking increase a woman's risk of developing cancer of the breast, liver and rectum — and in smokers, cancers of the mouth and throat," Naomi Allen of the University of Oxford, who led the study, said in a statement.

Low to moderate alcohol consumption may account for nearly 13 per cent of the cancers studied in Britain, the researchers said.

Women in the study had one alcoholic drink per day, which is typical of consumption in developed countries. About 25 per cent of the participants said they abstained. Nearly all the others reported fewer than three drinks a day.

The researchers compared the lightest consumers who had two or fewer drinks a week to those who drank the most.

The type of alcohol — whether wine, beer or liquor — did not change the link.

Participants were asked about their drinking habits while they visited breast cancer screening clinics. With an average followup time of more than seven years, 68,775 women were diagnosed with cancer.

Each additional alcoholic drink regularly consumed per day was associated with:

• 11 additional breast cancers per 1,000 women up to age 75.
• One additional cancer of the oral cavity and pharynx.
• One additional cancer of the rectum.
• An increase of 0.7 each for esophageal, laryngeal, and liver cancers.

For these cancers combined, there was an excess of about 15 cancers per 1,000 women per drink per day. That compares with the background incidence for these cancers of an estimated 118 per 1,000 women in developed countries, the researchers said.

"Although the magnitude of the excess absolute risk associated with one additional drink per day may appear small for some cancer sites, the high prevalence of moderate alcohol drinking among women in many populations means that the proportion of cancers attributable to alcohol is an important public health issue," the study's authors wrote.

No safe level

The message is clear, agreed Michael Lauer and Paul Sorlie of the National Heart, Lung, and Blood Institute in the United States.

"There is no level of alcohol consumption that can be considered safe," Lauer and Sorlie wrote in a journal commentary.

The observation is not a new one, but it's not a message that people want to hear, said Dr. Kathy Pritchard, an oncologist and head of clinical trials and epidemiology at Toronto's Sunnybrook Regional Cancer Centre.

The reason alcohol is a risk factor is it affects your liver. Both men and women who drink alcohol have more estrogen in their system, Prichard said.

In the U.S., guidelines recommend that women consume no more than one drink a day and two a day for men.

"You have to balance all those things out," said Dr. Philip Brooks, who researches alcohol and cancer at the U.S. National Institutes of Health. "This kind of information is important for people to know and to consult with their physician about the various risk factors they have."

With files from Associated Press