Coffee and Cancer: What’s the Link?

By: Courtney Henrich

Editors’ Note: This post is from a Human Health course titled “Nutrition and Health Mythbusters” taught by Dr. Myra Woodworth-Hobbs. Dr. Woodworth-Hobbs briefly describes the course and assignment below:

Nutrition is at the center of a cultural dialogue about health, though to most people the line between ideology and scientific knowledge is increasingly unclear. The confusion surrounding what to eat for health is fueled by misrepresentation of research findings in popular media and misapplication of the scientific evidence by those marketing fad diets, weight loss schemes, and dietary supplements. In Nutrition and Health Mythbusters, we examine the scope and strength of different types of evidence in nutrition science and how this evidence informs dietary recommendations for individuals and populations. Throughout the course, students to use this knowledge to evaluate nutrition information in the media and translate scientific research to both an academic audience and the general population. For the final project, they research a current nutrition- or health-related topic and synthesize their findings in the form of an evidence-based op-ed and infographic. Below, we present one of these student’s projects. Next week, we will post another student’s work.

In every cup of coffee, there is a chemical linked to cancer. That stands an undisputed fact and is the subject of an ongoing legal case in California. Last year, a nonprofit group, the Council for Education and Research on Toxics, sued 91 coffee companies for not warning consumers about a particular chemical produced when coffee beans are roasted.

The chemical, called acrylamide, can also be found in French fries, toast, and breakfast cereals. In March, a judge ruled that in accordance with Proposition 65, coffee sold in California must come with cancer warnings. Proposition 65 is a California state law that requires businesses to alert residents about significant exposures to toxic chemicals and has issued warnings about everything from boats to wooden furniture. Even though the World Health Organization (WHO) issued a public statement shortly after stating there is “inadequate evidence” that drinking coffee causes cancer, coffee shops in California must comply with the law and post a warning.

For more than 15 years, scientists have tried to decipher whether or not acrylamide negatively affects human health in the doses we consume. The only evidence that may have some validity to it is that coffee consumption is associated with bladder cancer. While most of the research has been disproved after adjusting for smoking status, there is limited research that stands to suggests there is an increased risk between coffee consumption and bladder cancer, especially in male coffee drinkers.[1]

Acrylamide has been shown to increase the risk of various types of cancer in rats and mice – at least when they’re exposed to extremely high doses – but, according to the American Cancer Society, no such link has been confirmed in humans.[2] In 2011, research that included over 2 million participants assessed the association between coffee intake and cancer risk in humans and found that coffee consumption was not associated with an increased risk of cancer.[3] A different study, published just two years ago, came to the same conclusion: coffee consumption is not associated with overall cancer risk.[4]

So, your morning dose of caffeine won’t hurt you, but could your Starbucks habit actually help improve your health? For some types of cancer, this may be the case. Coffee consumption has been found to be inversely associated with risk of oral, pharyngeal, colon, liver, prostate, and endometrial cancer. Research in Japan suggests that people who drink 2-4 cups of coffee per day have a 43% lower risk of liver cancer and those who drink 5+ cups have a 76% lower risk of liver cancer in comparison to those who do not drink coffee.[5] These findings support the claim that habitual coffee drinking may be associated with a reduced risk of liver cancer.

The evidence is not conclusive enough to change your morning routine over a few weak claims and a controversial news story out of California.

In May 2016, a group of 23 scientists from ten countries met at the International Agency for Research on Cancer (IARC) to dig deep into the coffee-cancer controversy and concluded that coffee drinking does in fact protect from liver and esophageal cancers.[6,7]. The mechanism behind coffee’s ability to reduce the risk of liver cancer is hypothesized to be linked to its prevention of elevated hepatic transaminases, a marker of hepatic disease and major contributor to cirrhosis. However, the hypothesis needs further investigation to prove that this is how coffee benefits our liver health.

What doesn’t need any further investigation, though, is your coffee habit. There is no need for lawyers to be suing Starbucks or Dunkin’ or for you to put the Keurig away. The evidence is not conclusive enough to change your morning routine over a few weak claims and a controversial news story out of California. Stay calm and drink up — there are more positive health benefits to moderate coffee consumption than there are risk factors. Instead of worrying about how much coffee you drink, start paying attention to what goes into your coffee before you drink it. Drowning that elegant Columbian roast with heavy cream and sugar surely won’t improve your health.            

Make the switch to black coffee as much as you can or maybe mix it up with a cup of hot tea. Plus, know your limits. If you’re very sensitive to caffeine, think twice about that 4pm espresso that will keep you up all night — sleep is proven to be a vital component to your long-term health. Don’t drink coffee because you think it might help you live longer, or stay away from it because you think it might kill you, drink it because you enjoy a freshly brewed cup or two.

References

1. Wu, W., Tong, Y., Zhao, Q., Yu, G., Wei, X., & Lu, Q. (2015). Coffee consumption and bladder cancer: a meta-analysis of observational studies. Scientific reports, 5, 9051. doi:10.1038/srep09051
2. Pelucchi, C., Bosetti, C., Galeone, C. and La Vecchia, C. (2015), Dietary acrylamide and cancer risk: An updated meta‐analysis. Int. J. Cancer, 136: 2912-2922. doi:10.1002/ijc.29339
3. Yu X. et al. (2011) Coffee consumption and risk of cancers: a meta-analysis of cohort studies. BMC Cancer, 11:96. doi: 10.1186/1471-2407-11-96
4. Alicandro G. et al. (2017) Coffee and cancer risk: a summary overview. Eur J Canc Prev, 424-432. doi: 10.1097/CEJ.0000000000000341
5. Inoue M. et al. (2005) Influence of coffee drinking on subsequent risk of hepatocellular carcinoma: a prospective study in Japan. J Natl Cancer Inst. 16;97(4):293-300. doi: https://doi.org/10.1093/jnci/dji040
6. Loomis D. et al. (2016) Carcinogenicity of drinking coffee, mate, and very hot beverages. The Lancet Oncology, 17(7):877-878. doi: 10.1016/S1470-2045(16)30239-X
7. Bravi F, Tavani A, Bosetti C, Boff etta P, La Vecchia C. (2017) Coffee and the risk of hepatocellular carcinoma and chronic liver disease: a systematic review and meta-analysis of prospective studies. Eur J Cancer Prev 368-377.doi: 10.1097/CEJ.0000000000000252.