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Critique 200: Does Light Drinking Increase the Risk of Cancer? — 8 June 2017

The association between the consumption of alcohol and the risk of cancer has been of great interest for many decades. There are a number of types of cancer, especially those of the upper aero-digestive tract (such as mouth, tongue, pharynx, etc.) that are clearly increased among heavy drinkers, especially among subjects who are also heavy smokers. Cancer of the liver can be a result of alcoholic liver cirrhosis, related to long-term heavy drinking. Further, an increased risk for many other cancers have been shown for heavy drinkers, but generally not for light or moderate drinkers.

The risk of breast cancer in women, however, is usually found to be slightly higher in even light drinkers than it is among non-drinkers. This has been a common finding, although some studies suggest that the pattern of drinking, the estimated level of underreporting of alcohol intake, use of hormone replacement therapy, and level of folate intake may all affect this association. For colorectal cancer, some studies suggest an increase in risk even among light-to-moderate drinkers. This has led some to proclaim that no alcohol consumption is preferable for the prevention of cancer. Others suggest that it is important to consider not only cancer, but other diseases; for example, coronary heart disease, ischemic stroke, diabetes, and dementia (all of which are important causes of disability and death) occur less frequently among moderate drinkers than among non-drinkers. Further, the risk of total mortality is almost always found to be lower among light to moderate drinkers than among abstainers.

The present analysis was designed to help determine the association of light or moderate drinking with the risk of cancer. It consisted of a meta-analysis based on a total of 60 studies from 135 articles and included only cohort studies of high quality. The analysis focused on the association between very light (≤0.5 drink/day), light (≤1 drink/day), or moderate drinking (1-2 drinks/day) and the risk of cancer incidence and mortality.

The authors found that very-light drinking was not associated with the incidence of most cancers except for female breast cancer and male colorectal cancer, and was associated with a decreased incidence of both female and male lung cancer and both female and male thyroid cancer. Moderate drinking significantly increased the incidence of male colorectal cancer and female breast cancer, whereas it decreased the incidence of both female and male hematologic malignancy.

Forum members considered this to be a well-done meta-analysis, based on a large number of studies. The main weaknesses of the study related to the lack of ability of the authors to evaluate a number of known confounders: underreporting of alcohol intake, the pattern of drinking or the type of beverage consumed, socio-economic status, and folate intake or other dietary factors. Further, the authors did not describe the effects of alcohol consumption on total mortality.

The results of this study, obviously, support most previous epidemiologic evidence on the association between alcohol consumption and cancer. Larger amounts of alcohol are associated with increased risk of a number of cancers, and even light consumption is associated with the risk of breast cancer, and possibly colorectal cancer. However, given the inability to adjust for many confounders in this study, and lack of data on the net effects in terms of total mortality, it remains difficult for scientists to provide scientifically sound and balanced guidelines regarding the health consequences of alcohol consumption that are applicable to everyone in the population.

Reference: Choi Y-J, Myung S-K, Lee J-H. Light Alcohol Drinking and Risk of Cancer: A Meta-analysis of Cohort Studies. Cancer Research and Treatment 2017; pre-publication release..

For the full critique of this paper by members of the International Scientific Forum on Alcohol Research, please click here.
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