People who engage in light or moderate drinking every day are at an increased risk of cancer, a study has found.
Research carried out in the United States and published by the BMJ only found the link in men who had smoked at some point in their lives, and not in those who had never been a smoker.
But even in women who had never smoked, the risk of alcohol-related cancers - mainly breast cancer - increased even after one alcoholic drink a day.
An accompanying editorial in the BMJ said people with a family history of cancer, particularly women with a family history of breast cancer, should consider reducing their alcohol intake to below the recommended limits.
Researchers said that because smoking is a major risk factor for most alcohol-related cancers - apart from female breast cancer - the apparent influence of alcohol on cancer could be partly driven by its effect among smokers.
Light or moderate drinking was classed as less than 15g (around one-and-a-half units or just under two drinks) a day in women and 30g (three units or three or four drinks) and below in men.
The study of more than 88,000 women and 47,000 men aged over 30 found the median consumption of alcohol was 1.8g a day in women and 5.6g in men.
Other findings were that abstainers or heavy drinkers were less likely than light and moderate drinkers to have had regular physical examinations by their GP and be screened for colorectal, prostate, or breast cancer.
They also engaged in fewer physical activities and had lower dietary scores. Heavy drinkers were more likely to be long-term smokers.
Breast cancer was the leading alcohol-related cancer in women, while colorectal cancer was the major alcohol-associated cancer in men.
For alcohol-related cancers, increased frequency of drinking was associated with increased risk in men but not in women, whereas binge drinking was associated with increased risk in women but not in men.
The study, which was led by Harvard TH Chan School of Public Health in Boston, Massachusetts, said it is estimated that alcohol consumption has caused 3.6% of all cancers worldwide - 1.7% in women and 5.2% in men.
An accompanying editorial in the BMJ by Dr Jurgen Rehm of the Centre for Addiction and Mental Health in Toronto, Canada, said more research is needed, and is becoming increasingly possible in high income countries where the number of non-smokers has increased while alcohol consumption has been relatively stable.
"Finally, people with a family history of cancer, especially women with a family history of breast cancer, should consider reducing their alcohol intake to below recommended limits, or even abstaining altogether, given the now well established link between moderate drinking and alcohol-related cancers," he added.
Dr Richard Roope, clinical lead for cancer at the Royal College of GPs, said: "We have known about the strong link between alcohol and cancer for some time, but this study serves as a useful reminder about how pronounced this is, especially when coupled with smoking, and when people have a family history of cancer.
"According to recent figures, 30% of bowel cancers, 21% of oesophageal cancers, 12% of bowel cancers and 6% of breast cancers in women are all associated with alcohol every year.
"GPs do not want to be killjoys - but we want our patients to live long and healthy lives and lifestyle habits, such as smoking and drinking alcohol, are very real risk factors in developing cancer that can't be ignored."