Drinking a bottle of wine per week is equivalent to smoking five to 10 cigarettes a week when it comes to increasing the lifetime risk of developing cancer, according to a new study that has received widespread mainstream news coverage.
The UK study was both lambasted and praised by experts approached by Medscape Medical News.
For women, consumption of one bottle of wine per week increased the absolute lifetime risk of cancer to the same extent as smoking 10 cigarettes a week, largely driven by a heightened risk of breast cancer.
Among men, drinking a bottle of wine per week boosted the absolute lifetime risk of cancer equivalent to smoking five cigarettes.
The findings were published online March 28 in BMC Public Health. While there has been a great deal of literature and research looking at both cigarettes and alcohol and their respective cancer risk, this is the first paper to compare them head to head. "We simply performed a calculation based on data from previous large epidemiological studies as described in our methodology," said first author Theresa Hydes, MBBS, PhD, a hepatology clinical fellow at the University Hospital Southampton, England. She noted that the cigarettes equivalent was used primarily to help raise public awareness of the risk between alcohol and cancer.
"The public associates alcohol with liver disease but are generally not aware that it is the fifth leading cause of cancer and of course drinking rates are continuing to increase in many countries," Hydes told Medscape Medical News.
Two experts approached for an independent comment by Medscape Medical News offered differing viewpoints of the study.
Ruth Etzioni, PhD, a biostatistician at Fred Hutchinson Cancer Research Center in Seattle, Washington, was not convinced that comparing cigarettes and alcohol is helpful to the public.
The title of the paper includes the phrase "How many cigarettes are in a bottle of wine?" According to Etzioni, this shows it was "obviously written to grab attention." Adding, "I would recommend giving it as little attention as possible."
"The cancers induced by smoking, which are very clear, are not the same as the cancers supposedly affected by alcohol — which are a lot less clear," Etzioni explained. "Making this comparison is not helpful and is guaranteed to cause alarm. There is a lot more uncertainty about the risk induced by alcohol consumption than about cigarette smoking."
The study is a disservice to health-conscious lay people, suggested Etzioni. "This is the kind of work that makes people trying to take decent care of their health tear their hair out."
Another expert, however, felt the paper has merit.
"Public health professionals and possibly the public have often speculated about alcohol risks compared to smoking, and this excellent, clear paper provides this information," commented Mark Petticrew, PhD, professor of public health evaluation in the Faculty of Public Health and Policy at London School of Hygiene and Tropical Medicine, England. "For that reason it is an unusual and important paper."
He added that the authors are not "scaremongering" and they say so. "The paper starts by saying 'we must first be absolutely clear that this study is not saying that drinking alcohol in moderation is in any way equivalent to smoking,'" said Petticrew. "The analysis also looked at cancer in isolation, and alcohol causes other health problems which need to be considered."
One Bottle of Wine Ups the Risk
In this study, Hydes and colleagues estimated the increase in the absolute risk of developing cancer as it related to moderate consumption of alcohol and compared it to the increase in absolute risk of developing cancer secondary to smoking.
The authors used the lifetime cancer risk data from Cancer Research UK to calculate the possible lifetime cancer risk associated with consuming 10 units of alcohol or 10 cigarettes per week. Alcohol and tobacco attributable fractions were then subtracted from lifetime general population risks of developing alcohol- and smoking-related cancers in order to estimate the lifetime cancer risk in alcohol-abstaining nonsmokers. This was then multiplied by the relative risk of drinking 10 units of alcohol or smoking 10 cigarettes per week, and increasing levels of use.
Their results showed that among nonsmoking men, the increase in the absolute lifetime risk of cancer from drinking one bottle of wine per week was 1.0%, while for nonsmoking women, the risk was about 50% higher at 1.4%.
In men, the increased cancer risk manifested primarily in gastrointestinal cancers (eg, oropharynx, esophageal, colorectal, liver); in women, breast cancer accounted for 55% of additional cases. The authors emphasized that this finding was important because smoking is also an important cause of GI tract cancers but not breast cancer. Therefore, if 1000 men and 1000 women each consumed one bottle of wine per week, an estimated 10 men and 14 women would develop cancer as a result.
They next compared the percentage increase in absolute lifetime risk of all alcohol and tobacco-related cancers for smoking 10 cigarettes per week or drinking 10 units of alcohol per week. This showed that low levels of smoking carried the greatest risk for men (2.1% absolute risk [AR] per 10 cigarettes, 1.0% AR per 10 units of alcohol) and that the cancer risk was seen across all smoking-related malignancies.
For women, this increase was comparable (1.5% AR per 10 cigarettes, 1.4% AR per 10 units of alcohol) due to breast cancer incidence being partly driven by alcohol use.
Not surprisingly, as the amount of alcohol intake increased, so did the lifetime risk of alcohol-related cancers. Drinking three bottles of wine per week or about half a bottle per day, was associated with an increase of absolute lifetime cancer risk to 1.9% in men and 3.6% in women, or 19 in 1000 men and 36 in 1000 women, respectively. This extrapolated to smoking about eight cigarettes per week for men and 23 cigarettes per week for women.
"We are clear that there are no health benefits from drinking," said Hydes. "While these studies are often bought up by the alcohol industry — overall their findings have now been discredited, often due to the fact that the teetotalers in these studies have abstained due to health reasons and therefore skewed the data. There is now robust evidence that low levels of alcohol intake do not provide any protective health benefits."
She added that the World Health Organization's International Agency for Research on Cancer, the World Cancer Research Fund, and the American Institute for Cancer Research have all stated that no level of alcohol consumption is completely safe, which led to adjustment of the UK sensible drinking guidelines in 2016 to state that no level of alcohol consumption is completely safe.
Alcohol and the Heart
Petticrew also pointed out that while some literature has found that there may be a protective relationship between alcohol and heart disease, it is unclear and there may be other explanations for the relationship. "Even if such a protective effect is real — which is disputed — it only relates to heart disease and there are about 200 other conditions which alcohol increases the risk for, including cancer."
Importantly, at low levels of consumption, the risk of cancer is low, Petticrew explained. "Also, in terms of alcohol and heart disease — if there is a protective effect, it occurs at very low levels."
In terms of communicating this information with the public, the study does raise other questions. "It is important to know how the public would respond to messaging, which describes alcohol risk in terms of cigarettes smoked," he added. "We don't know enough about this. Does the public think that the small increased risk is 'worth it'? Will they reject such messages? This would be an important study to carry out."
The study authors emphasized that while their new data represent a realistic comparison, "it must be understood that the risks described are population-level risks, such as that the cancer-causing effect of 10 units of alcohol a week or 10 cigarettes a week will vary on an individual level due to other lifestyle issues, genetics, etc."
Lead author Hydes also pointed out that even though they went to great lengths to correct for the synergistic effect of both drinking and smoking "this will still be an issue. If you drink and smoke the cancer risks multiply rather than being additive."
While the health risks of smoking are well established and widely understood by the public, the situation is different with alcohol, especially as it relates to cancer. Even though studies have established alcohol drinking as a risk factor for multiple malignancies, awareness in the general public is low. In a 2017 poll conducted by the American Society for Clinical Oncology, for example, 70% of Americans did not recognize drinking alcohol as a cancer risk factor, as previously reported by Medscape Medical News.
The study received no outside funding. Etzioni and Petticrew have disclosed no relevant financial relationships.
BMC Public Health. 2019;19:316. Full text
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