A Drink a Day May Boost Risk for Certain Cancers

Roxanne Nelson

August 21, 2015

Another study showing an increased risk for cancer with drinking alcohol, even with just one or two drinks a day, has prompted renewed warnings on the health risks associated with alcohol consumption.

The new study, from an analysis of more than 150,000 healthcare professionals in the United States, found that overall, light to moderate drinking (alcohol intake of <15 g/day for women and <30 g/day for men) was associated with a small but nonsignificant increase in cancer risk in both women and men.

But this risk was more defined in specific populations. In men, the association was apparently driven by tobacco use. But for women, even one drink a day was associated with an increased risk for alcohol-related cancers, primarily breast cancer, and this was unrelated to smoking status.

The study was published online August 18 in the BMJ.

In an accompanying editorial, Jürgen Rehm, PhD, from the Centre for Addiction and Mental Health in Toronto, Canada, notes that the elevated risks for certain cancers associated with light and moderate drinking are important and have been partly confirmed by the current study.

Current guidelines relating to alcohol consumption consider overall risks to health and are not just for cancer, he comments.

"However, even when we consider all cause mortality attributable to alcohol, drinking more than 10 g of pure alcohol per day for women or 20 g for men over a lifetime can lead to a magnitude of risk not considered acceptable for voluntary behaviour in modern societies," writes Dr Rehm.

 
...can lead to a magnitude of risk not considered acceptable for voluntary behaviour in modern societies. Dr Jürgen Rehm
 

This study does not challenge those limits, and the cited upper thresholds "are also roughly in line with the upper limits of many national guidelines."

Dr Rehm also advises that those "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."

In addition, although minimal information on family histories of cancer was available, the authors did observe a stronger association of alcohol intake and overall cancer among people who had a family history of colorectal cancer. However, there were minimal differences among people with a family history of breast cancer compared with those without one.

Consider Reducing Intake

Dr Rehm questions what to make of the fact that the higher cancer risk associated with light to moderate drinking appears largely linked to lifetime ever-smokers.

"This could be the result of an interaction between smoking and drinking on risk for cancer," he notes, or it could be a confounder, but more research is definitely needed.

"Such research is becoming increasingly possible in high income countries, where the number of never smokers has increased while alcohol consumption has been relatively stable," says Dr Rehm.

Defining the Smoking Angle

Last year, the 2014 World Cancer Report, issued by the World Health Organization's International Agency for Research on Cancer (IARC), declared that no amount of alcohol is safe. The IARC put alcohol on the list of carcinogens back in 1988. But the risk is dose dependent ― the more alcohol that a person drinks, the higher the cancer risk ― and the study authors note that the association of cancer with light to moderate drinking is less clear.

The authors, led by Edward L Giovannucci, MD, ScD, professor of nutrition, Harvard T. H. Chan School of Public Health, Boston, also wanted to clarify the role of alcohol consumption independently of smoking, because that "has not been settled." Heavy drinkers are more likely to smoke, and although the analyses adjusted for smoking, residual confounding may exist.

Smoking is also the major risk factor for most alcohol-related cancers, aside from female breast cancer, and in studies that include tobacco use, the apparent influence of alcohol on cancer could be partly driven by its effect among smokers, they point out.

Women and Smokers at Risk

For their study, Dr Giovannucci and his team used data from two ongoing prospective cohort studies: the Nurses' Health Study, which included 121,700 female nurses aged 30 to 55 years at enrollment in 1976, and the Health Professionals Follow-up Study, which included 51,529 male health professionals aged 40 to 75 years at enrollment in 1986. They assessed the association between light to moderate drinking and cancer, as well as how alcohol consumption affects cancer risk in the absence of tobacco use.

Of the defined alcohol-related cancers (affecting the colorectum, female breast, oral cavity, pharynx, larynx, liver, and esophagus), there were 9016 cases in women and 1611 cases in men documented during follow-up. Breast cancer was the leading alcohol-related cancer in women, and colorectal cancer was predominant in men.

The associations between light to moderate drinking and risk for total cancer were similar regardless of smoking history, but consuming alcohol above moderate levels (Pinteraction = 0.06 for women and 0.11 for men) was more strongly associated with risk for cancer among ever-smokers compared with those who never smoked.

Among women, alcohol consumption of 5 to 14.9 g/day was associated with increased risk for alcohol-related cancer (relative risk, 1.13; 95% confidence interval, 1.06 - 1.20), which was primarily driven by breast cancer. It was similar regardless of smoking status and after controlling for obesity and other covariates.

Conversely, the risk for alcohol-related cancers (among light and moderate drinkers) only increased among men who ever smoked (Ptrend = 0.006) but not among those who never smoked (Ptrend = 0.18).

The authors also found that the relationship between total cancer and alcohol was not "appreciably" different when they looked at possible confounders, such as age, multivitamin or aspirin use, Alternative Healthy Eating Index 2010, or family history of breast cancer among women. However, it was stronger among those with a family history of colorectal cancer, although the interactions were not significant.

"Among women, even consumption of up to one drink per day was associated with increased risk of alcohol related cancers (mainly breast cancer)," conclude the authors. "Decisions on levels of alcohol consumption should also incorporate information on smoking history and familial predispositions to alcohol related cancers."

The study was supported by grants from the US National Institutes of Health. The authors and Dr Rehm have disclosed no relevant financial relationships.

BMJ. Published online August 18, 2015. Full text, Editorial

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