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SKEPTOID BLOG:

Does Drinking White Wine Give You Melanoma?

by Stephen Propatier

December 9, 2016

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Donate Brown University put out a press release this month about some of its soon-to-be-published research. The study, named "Alcohol Intake and Risk of Incident Melanoma: A Pooled Analysis of Three Prospective Studies in the United States," appears this month in Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research. It looks at the drinking habits of more than 210,000 participants, and found bad news for those who enjoy a glass of white wine: the findings suggests that drinking white wine will significantly raise your risk for melanoma! Or so the media reports would have you think. Regular Skeptoid readers will be familiar with the paucity of such science reporting: sensational headlines with unsupported conclusions often dominate such news. Let's take a close look at this research and determine if this pop-science flavor-of-the-week is in fact science, or just science fiction.

In the interest of full disclosure, I should note that one of the principal investigators for this study is from my affiliated university: Eunyoung Cho, Sc.D., an associate professor of dermatology and epidemiology at the Warren Alpert Medical School of Brown University in Providence, Rhode Island.

The results were interesting. Overall alcohol intake was associated with a 14 percent higher risk of melanoma per drink per day. Each drink per day of white wine was associated with a 13 percent increased risk of melanoma. Other forms of alcohol—beer, red wine, and liquor—did not significantly affect melanoma risk.

This is just one piece of data supporting a growing body of evidence indicating that alcohol is associated with several types of cancer. What was surprising about this research is the high association with skin cancer lesions (melanoma) in low-exposure areas—finding cancer on areas of the skin that don't get a lot of sun. Obviously, that is considered unusual since cancer correlates best with sun exposure/damage. Secondly there was one significant blip that has drawn all the media attention, namely that white wine in particular had a much higher association with melanoma. According to reporting in EurekAlert!:
Cho said that compared with nondrinkers, those who consumed 20 grams or more of alcohol per day were 2 percent more likely to be diagnosed with melanomas of the head, neck, or extremities, but 73 percent more likely to be diagnosed with melanomas of the trunk.
Dr. Cho also commented:
It was surprising that white wine was the only drink independently associated with increased risk of melanoma. The reason for the association is unknown. However, research has shown that some wine has somewhat higher levels of pre-existing acetaldehyde than beer or spirits. While red and white wine may have similar amounts of pre-existing acetaldehyde, the antioxidants in red wine may offset the risks.
Does this study actually say that white wine causes melanoma? No, it doesn't,there are major flaws that put doubt on that conclusion. Here is why: all correlational studies have one common flaw, it is an association, not a causative link. Lay persons and media outlets fail almost universally on that distinction. A single study suggesting a possible association is no more definitive than saying drinking water causes car accidents. All people who have car accidents drink water; does drinking water cause car accidents? The correlation is very definitive if you see it replicated multiple times from different studies and types of studies, such as the correlation of lung cancer and smoking.

The most surprising finding is that white wine in particular had a significantly higher correlation than other alcohol. There are many reasons why that might be false conclusion, such as confounding cultural variables. What if the study had a high degree of white wine-drinking Scandinavians with albinism? It might be that the white wine drinkers were all fair skinned and passed out drunk in the sun, or they were nudists. Although these suggestions are unlikely they are not impossible. We don't know because they didn't really do the study with those types of controls in mind. The original structure was asking a more general question, so the correlation is at best weak, even if it is mathematically strong. It is interesting and worthy of further study, but without those controls in place for those factors we really don't know what this says.

Additionally the study had a major flaw that is significant for melanoma. It didn't control for sun exposure. The single biggest factor in skin cancer wasn't controlled for. That really drives a wedge into any causality statements for white wine. There is no evidence at all for the the statement by the researcher that chemicals in the wine are the causative factor. That is pure speculation by the researcher suggesting a cause of an unknown with another unknown.

Nonetheless, following the press release, white wine has been widely reported as raising the risk for melanoma. This is another example of poor science reporting. Research is often offered by the news media outlets as isolated factual Truth. Skeptoid listeners know that scientific knowledge is rarely revolutionary. Rather, it's built brick by brick until you have a solid hypothesis with multiple lines of evidence supporting it. This study is just one piece of new evidence; it is an association, and not a very definitive one.

Press attention is always good when you're looking to fund further research, but trying to get it can lead to one's work being wildly misrepresented. This is a common flaw in the game that researchers play with the news media: trying to call attention to their research by expounding on some new finding that makes their research more catchy and newsworthy. It takes a finding, such as here the correlation of increased risk of cancer with alcohol, and puts a headline-grabbing spin on the research. Does it mean that the research is fabricated or false? No, it doesn't. It is a very subtle discussion that the press extrapolates from freely to make the story more interesting. In practice it is a win-win for researchers and media outlets. But the science-illiterate reporting works to the detriment of the public. In this case, such exaggeration is probably not harmful, but definitely inaccurate.

So what is the definitive answer? Does white wine cause cancer? Truth be told we don't know. We have a pretty well structured study that suggests a unexpected finding, with a plausible but unsupported guess as its mechanism. Based on this one study I don't think your dermatologist is going to recommend you stay away from white wine just yet. It is an interesting finding that deserves a focused, controlled, and well-structured scientific evaluation. I suspect in the end that we will find that this was statistical noise generated from the large number of subjects in the study. I hope I am not wrong, I would hate to think that a nice glass of Riesling is as dangerous as getting a sunburn.

That is the beauty of the scientific method, its ability to answer these questions. Despite the news reports, white wine causing melanoma has not been answered. Realistically we just have found the question.

Whenever you see a new fantastic and exciting medical discovery broadly disseminated throughout the media, remember you have good reason to be skeptical.

Take a minute and support Skeptoid. The money doesn't go to me, but instead goes to keep Skeptoid running as a resource of science and skepticism. Remember: all donations and gifts to Skeptoid Media, Inc. are tax deductible under section 501(c)(3) of the Internal Revenue Code (sections 170, 2055, 2106, 2522).

You can follow me at Twitter @steveproacnp for a daily dose of skeptical nursing.

Disclaimer: This post is my personal opinion, it is not a substitute for medical care. It is for informational purposes only. The information on Skeptoid blog is not intended nor recommended as a substitute for medical advice, diagnosis, or treatment. Always seek the advice of your own physician or other qualified health care professional regarding any medical questions or conditions. This post does not reflect the opinion of my partners, professional affiliates, or academic affiliations. I have no financial conflicts of interest to disclose.

by Stephen Propatier

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