Coffee Conundrum Shows How Trouble Is Brewing in Lifestyle Cancer Research

OncologyLive, Vol. 17/No. 20, Volume 17, Issue 20

Twenty-five years ago, WHO declared that coffee was a potential carcinogen. Now, the public health agency has reversed course, raising a host of questions about the accuracy and value not only about the original research but also about the recent report.

Maurie Markman, MD

"Are they serious?" How often have many in the clinical cancer community asked this question about purported scientifically based reports in the peer-reviewed or lay press, or both, which appear to be making confusing, dubious, or even potentially dangerous claims?

Concern is heightened by the rather remarkable proliferation of peer-reviewed “academic journals” created by what have been labeled “predatory publishers,” with many of these entities having distressingly serious questions about their basic credibility.1

As a result, it is unfortunately becoming quite easy for an investigator, or group of investigators, to claim that their results or conclusions have been “peer reviewed.” (Over the past several months, I have received email requests to become an editorial board member of 5 such journals whose existence I had no knowledge of prior to this date, and I reasonably assume this is an increasingly common request of my colleagues.)

Changing Coffee Warnings

However, one need not venture outside the realm of well-recognized and highly regarded cancer organizations to learn of concerning reports that might potentially lead to a loss of faith by the general public in the scientific objectivity or value of such groups.Consider, for example, the recent pronouncement by the highly regarded World Health Organization (WHO) that “coffee is unlikely to cause cancer” when for the last 25 years this organization has labeled this extremely widely consumed beverage as being “possibly carcinogenic to humans.”2

The questions to be directed to WHO are fairly obvious: Considering the known consumption of this product and the worldwide economic impact of the beverage, was the available evidence 2 decades ago truly sufficiently strong that it was appropriate for this public health agency to make such a stunning and frightening claim? What exactly has really changed such that it is reasonable today to state that drinking coffee is now safe? Finally, is WHO ultimately simply admitting that the methodology employed in such research runs the serious risk of producing false or, at a minimum, strikingly misleading results?

In light of the extreme importance and public health relevance of epidemiological efforts that have unequivocally defined the definitive role of asbestos in the development of malignant mesothelioma, HPV in cervix cancer, and tobacco in multiple malignancies, the pronouncement of questionable claims that are later retracted has the very serious potential to undermine societal confidence in this effort.

In addition, one wonders whether WHO somehow believes that it has a mandate or an obligation to publish such reports based on some prospectively determined, statistically defined result, rather than inquiring if the observed outcomes are clinically meaningful, whether anyone associated with this group considers how their pronouncement will be received by the public, and whether such statements would likely have an overall positive or negative impact on public health.

Based on both the questionable justification for the initial pronouncement that coffee consumption is “possibly carcinogenic to humans” and the stated reasons for the reversal, it is reasonable to conclude that the public may have a more difficult time accepting a future claim about a potential health risk, no matter how good the quality of the available data and the suggested seriousness of its consequences.

Alas, we did not have to wait long to learn of the value of this organization’s pronouncements as they have now declared that beverages above 65°C (“piping hot tea”) are “possibly carcinogenic.”2

The Citrus Problem and Melanoma

To be clear, there may very well be legitimate scientific support for the conclusions reached by this healthcare agency. However, with the large and increasing number of recognized truly relevant and serious worldwide health-related concerns, including international efforts in tobacco control, some observers may be left speechless upon learning how the WHO is spending its time and resources on behalf of the public.Unfortunately, the uncertain value of scientific endeavors is not limited to large public health efforts.

Consider the recent publication in a high-impact oncology journal that reported greater “citrus consumption was associated with an increased risk of malignant melanoma in 2 cohorts of women and men.“3

The investigators were not only making such a stunning claim about citrus products in general, but were in fact highlighting the potential role specifically of grapefruit consumption.

In addition to the obvious concerns about the objective quality of self-reported details of daily living (including food intake) during long-term survey research, highlighted in a recent lay publication,4 there were specific scientific issues raised with other aspects of this analysis.5

These included the overall strength of the stated association, the relevance of the unique patient population evaluated, the type of melanoma observed, and the observation that the authors reached conclusions regarding other risk factors that were strikingly different from previous well-regarded scientific publications in this arena.5

So, the fundamental question to be raised here is how such a flawed report, with a conclusion that could easily scare the public, would be accepted for publication in a high-impact medical journal?

And to be even more provocative, at a time when great concern has been expressed for the adequacy of public funding for vitally important cancer-related research, we must ask, is this the optimal manner in which to use our increasingly limited resources?

Maurie Markman, MD, editor-in-chief, is president of Medicine & Science at Cancer Treatment Centers of America, and clinical professor of Medicine, Drexel University College of Medicine.


  1. Moher D, Moher E. Stop predatory publishers now: act collaborati­vely. Ann Intern Med. 2016;164(9)­616­617. doi:10.7326/M15­3015.
  2. Coffee and cancer [Seven Days]. Nature. 2016(7608);534:440­441. doi:10.1038/534440a.
  3. Wu S, Han J, Feskanich D, et al. Citrus consumption and risk of cuta­neous malignant melanoma. J Clin Oncol. 2015;33(23):2500­2508. doi:10.1200/JCO.2014.57.4111.
  4. Kolata G. Food and exercise studies have one big problem. The New York Times. August 11, 2016:A3.
  5. Berwick M. Dietary advice for melanoma: not ready for prime time [editorial]. J Clin Oncol. 2015;33(23):2487­2488.