Caffeine, Coffee, and Breast Cancer—What’s the Answer?

Allison Manderfield

Writer’s Comment: As a senior graduating from UCD, I have become convinced that coffee is absolutely essential to receive a diploma from this university. And as a Genetics major, I am also intrigued by the complex interactions of lifestyle choices (like caffeine consumption) with genetic predispositions to disease. In my “Writing in the Professions: Science” course, I decided to explore the relationships among caffeine, genetics, and breast cancer and wrote an extensive collaborative literature review on this topic. Later, I wrote “Caffeine, Coffee, and Breast Cancer ­- What’s the Answer?” to communicate this scientific issue to a more general public audience. By using a women’s health magazine style, I hoped to educate women about the current research involving caffeine, genetics and breast cancer risk to enable them to make more informed lifestyle choices. Many thanks to Dr. Rebekka Andersen for challenging me to get creative and transform this complicated issue to make it accessible to non-specialist readers (and also for all the help and support along the way). Now, after many revisions (and a realization that I actually love popular science writing!), I hope you enjoy this piece.

Instructor’s Comment: In my UWP 104E course, students conduct substantial secondary research on a scientific area of inquiry and communicate their findings to different audiences for a variety of purposes. Allison’s ability to understand complex scientific ideas and convey those ideas in a clear, fluid, and interesting way made her a standout student in my fall 2010 course. But what particularly impressed me about Allison was her passion for demystifying science for non-scientists. When I introduced the popular science essay assignment, Allison jumped on the opportunity to write an essay for Women’s Health magazine about the interacting effects of caffeine intake and genetic variation on breast cancer risk, with the goal of demystifying breast cancer research for women wanting to minimize their cancer risk. What I especially enjoy about Allison’s piece is the way in which she uses an engaging writing style and draws on personal experience, metaphor, and imagery to help her readers understand the results of groundbreaking empirical studies and what those results mean for women who drink caffeine.
—Rebekka Andersen, University Writing Program

Warmed by the rays of morning sunlight that pour through the coffeehouse windows, I settle into my favorite chair. With a piping hot espresso in one hand and a genetics textbook in the other, I am ready for some serious finals preparation. Just as the caffeine begins to take effect and I become deeply engrossed in the molecular mechanisms of cellular development, I am startled by my phone’s buzz.

It is a very unexpected call from my friend Ana. Her voice falters as she tells me that her mom has just been diagnosed with Stage 3 breast cancer. I hang up and continue to sip my coffee in shock, my mind racing with unanswered questions. I have heard the recent statistics from the American Cancer Society that 1 in 8 women receive this diagnosis every year, but Ana’s mom is so healthy and fit—how could this happen to her? 

As a science student pursuing a degree in Genetics, I am already interested in what role the interaction of genetic and lifestyle factors play in breast cancer, and especially in recent rumors that diet might be linked to breast cancer. As a young woman,10–11 MANDERFIELD_Figure 1.jpg I also wonder if there is anything I can do now to lessen my chances of someday being included among the 1 in 8 unsuspecting women who will deal with this devastating diagnosis. I want to do what I can, even if it means I have to drastically change my eating habits or even give up my daily coffee routine. 

Swedish researchers at Lund University have similarly been wondering what lifestyle choices women can make to lessen their breast cancer risk. And ironically, they think that coffee may actually be one of the answers. Some of their latest research, led by Dr. Erika Bågeman, has suggested potential health benefits for women who drink coffee. They have shown that depending on a woman’s genetic predisposition, coffee’s caffeine may even lower breast cancer risks. 

Could Caffeine Cause Cancer?

The effects of caffeine on breast cancer risk have interested scientists for several decades, but our favorite caffeinated beverages weren’t always portrayed in a very positive light. As early as the 1970s, an Ohio medical doctor named J.P. Minton was examining the interaction between caffeine and breast cancer. He used mice as his model in one 1979 study and found that massive doses of caffeine caused many of them to contract breast cancer. This discovery caused great concern, but scientists and doctors realized that most women weren’t drinking hundreds of cups of coffee a day (the amount required to replicate the caffeine dosages given to the mice) and that the conclusions of Minton’s mouse study did not apply to women.

Unfortunately, Minton’s and other similar studies from that time received a lot of media attention, and myths regarding coffee’s harmful effects began to circulate and cause unwarranted worry.

In the years that followed, many researchers attempted to find any correlation between more realistic levels of caffeine intake and breast cancer incidence. They used questionnaires given both to breast cancer patients and to healthy women to see if women with cancer tended to drink more or less coffee and tea than those unaffected by the disease. Surprisingly, time and again, their results differed from those obtained by Minton’s early mouse studies and instead suggested that caffeine may not be the terrible carcinogen it had been made out to be. 

Some, like a 1985 study of American women by Boston University epidemiologist Lynn Rosenberg, found no association between drinking coffee and getting breast cancer. Researchers conducting studies in other countries have had similar findings. Some have found slight correlations that suggest coffee is either slightly useful or slightly harmful, but their results have been confounded by 10–11 MANDERFIELD_Figure 2.jpgother factors. For example, in one large study of over 14,000 Norwegian women, oncologist L.J. Vatten and her colleagues found that coffee drinking seems to decrease breast cancer risk for lean women but increase breast cancer risk for obese women. However, these researchers also admitted that additional factors such as smoking habits and general health could account for the differences in cancer incidence that they observed, rather than effects from caffeine. In 2002, a Swedish researcher named Karin Michels also unsuccessfully looked for a correlation between breast cancer and caffeine. She concluded that coffee neither increases nor decreases cancer risk. 

Could Genetics Be the Answer?

While early studies suggested that caffeine causes breast cancer, follow-up studies couldn’t find any conclusive association between caffeine intake and our breast cancer risk. That’s why Bågeman and her colleagues recently decided to take a different approach. They thought that genetics could potentially solve the caffeine and cancer mystery. Bågeman’s team wanted to determine if we could respond differently to caffeine intake based on our unique genetic make-up. Like a blueprint that tells construction workers how to build a building, the genes that make up our DNA tell our body how to build proteins. We have millions of genes, each of which directs our body to make a specific protein. Variations in our DNA blueprint direct our bodies to build slightly different proteins that cause us to have unique looks, behavior, and body function, with variations in everything from our hair and eye color to our hormone levels and response to caffeine.

In fact, we can even have variations in a gene that determines how our body processes the caffeine from that tall double espresso. One gene in particular, called CYP1A2, directs the formation of a protein that alters caffeine break down. This same protein also changes the path of estrogen breakdown. Doctors and scientists have known for a long time that estrogen (a female hormone) 10–11 MANDERFIELD_Figure 3.jpgplays a role in breast cancer development because it stimulates the growth of breast cells, even if they are cancerous. So any additional insight into how the body processes estrogen could be vitally important to understanding breast cancer risk. 

Erika Bågeman’s team found that the caffeine and estrogen metabolizing protein can slightly differ from one individual to another depending on what our DNA blueprint is at the CYP1A2 gene. These Swedish scientists don’t understand yet the exact mechanism of this caffeine and estrogen metabolism interaction, but they think it can affect breast cancer risk. Bågeman and her colleagues have found that the breast cancer risk of women with one variation of the CYP1A2 gene remains unchanged by caffeine consumption, while women with another variation, called the A/A variation, can actually decrease their breast cancer risk if they drink at least 3 cups of coffee every day. Their preliminary estimates suggest that about half of all women have the A/A variation in their DNA. 

Medical testing for the CYP1A2 gene variation is not yet available, but the research community generally agrees that drinking coffee in normal amounts is definitely not harmful and could possibly even be helpful, as Bågeman’s research demonstrates.

What’s the Bottom Line?

Go ahead and enjoy that coffee! The new research shows that if we are among the lucky people with the A/A gene variation, we’re actually reducing our breast cancer risk, and if we’re not, then our coffee isn’t helping us, but it’s not hurting us either. 10–11 MANDERFIELD_Figure 4.jpg

As I leave the coffeehouse that day after Ana’s phone call, I pause. Since downing another latte won’t increase my breast cancer risk and might even reduce it, I decide to give in to my caffeine craving and ask the barista for a refill.

Bågeman E, Ingvar C, Rose C, Jernström H. 2008. Coffee consumption and CYP1A2*1F genotype modify age at breast cancer diagnosis and estrogen receptor status. Cancer Epidemiology, Biomarkers & Prevention [Internet]. [cited 2010 Nov 28]; 17(4):895-901. Available from PubMed: http://,DanaInfo=cebp.aacrjourn...

Michels KB, Holmberg L, Bergkvist L, Wolk A. 2002. Coffee, tea, and caffeine consumption and breast cancer incidence in a cohort of Swedish women. Annals of Epidemiology [Internet]. [cited 2010 Nov 28]; 12(1):21-6. Available from PubMed:

Minton JP, Foecking MK, Webster DJ, Mathhews RH. 1979. Response of fibrocystic disease to caffeine withdrawal and correlation of cyclic nucleotides with breast disease. American Journal of Obstetrics and Gynecology; 135(1):157-8.

Osterweil, Neil. 2010. Coffee and your health. WebMD.
Rosenberg L, Miller DR, Helmrich SP, Kaufman DW. 1985. Breast cancer and the consumption of coffee. American Journal of Epidemiology 122(3):391-9.

Vatten LJ, Solvoll K, Løken EB. 1990. Coffee consumption and the risk of breast cancer. A prospective study of 14,593 Norwegian women. British Journal of Cancer [Internet]. [cited 2010 Nov 28]; 62(2):267-70. Available from PubMed:

“What are the Key Statistics About Breast Cancer?” American Cancer Society.


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