Its been a busy few weeks since my defense when I last blogged. We had a nice trip to DC to receive the Cozzarelli award from the National Academy of Sciences, then the following week I had my folks in town for graduation, and in between, did thesis corrections and paperwork. Yes, they don’t tell you but the paperwork is the worst especially when you have committee members in 3 cities (5 separate buildings)…
Last week was a semi-normal lab week, and now I’m in sunny San Diego for a little break to visit my friend Mary Canady…. So I thought I’d start blogging some real science, so thought I’d try a short-summary format for a few pieces of science that have been mentioned in the media recently, not necessarily in my areas of expertise. Let me know what you think of this format.
1) Coffee consumption decreases risk of ER-negative breast cancer
This is an interesting Swedish epidemiologic study published very recently in the open access journal Breast Cancer Research. The basic design of the study, which attempted to replicate previous studies, is what is called a case-control study, where 2,818 cases (ie patients) and 3,111 controls (non-breast cancer patients, matched as closely as they could) were analyzed. Importantly, pre-menopausal women and those who had other cancers previously (except non-melanoma skin cancer or in situ cervical cancer) were excluded so these results can only be extrapolated to the post-menopausal setting. A detailed
questionnaire allowed the correlation of tumor status with coffee consumption, and factors including HRT use, educational level and alcohol consumption also taken in account. The overall conclusion drawn was that high coffee consumption (defined as 5 cups per day) can modestly decrease the risk of ER-negative breast cancer (which is the more aggressive form that cannot be treated with anti-estrogen therapy).
My training in basic science of cancer biology leads me to postulate on some of the potential mechanisms of this protection, which are briefly proposed in the discussion section. Coffee is known to contain hundreds of chemicals, including caffeine and polyphenols which have the potential to act both as carcinogens or as chemo-preventive agents, and dissecting out which is responsible for the protection will be a challenge. Caffeine is known to be an inhibitor of the ATM/ATR proteins which I worked on in my PhD which are involved in sensing DNA damage and inducing repair, which would be an undesirable effect of high coffee consumption, however coffee is also the largest source of anti-oxidants in the US diet, and there are weakly estrogenic compounds such as trigonelline in coffee which would only promote the growth of ER-positive breast tumor cells but have no effect on ER-negative cells.
The major downside of this study is that it’s merely a correlation – establishing causation in vivo for something as widely consumed as coffee would be a major challenge. While it’s definitely possible that this negative relationship between coffee consumption and cancer risk is merely a marker of some other factor that is indeed correlated with cancer risk, I tend to doubt this explanation given what is known about the role of coffee in cancer risk in other tumor types as well, and the vast number of chemicals found in coffee that could possibly regulate steps involved in tumorigenesis.
So while this is not medical advice, I think it’s probably safe to say enjoy your coffee in moderation and there may be a potential health benefit in some circumstances.
OK I had thought of doing multiple articles per roundup (hence the #1 on my subtitle) but it seems maybe one is long enough. What do you think?
1. Allred KF, Yackley KM, Vanamala J, Allred CD. Trigonelline is a novel phytoestrogen in coffee beans. J Nutr. 2009;139:1833-8.
2. Arab L. Epidemiologic evidence on coffee and cancer. Nutr Cancer. 2010;62:271-83.
3. Ganmaa D, Willett WC, Li TY, Feskanich D, van Dam RM, Lopez-Garcia E, et al. Coffee, tea, caffeine and risk of breast cancer: a 22-year follow-up. Int J Cancer. 2008;122:2071-6.
4. Li J, Seibold P, Chang-Claude J, Flesch-Janys D, Liu J, Czene K, et al. Coffee consumption modifies risk of estrogen-receptor negative breast cancer. Breast Cancer Research. 2011;13:R49.
5. Tang N, Zhou B, Wang B, Yu R. Coffee consumption and risk of breast cancer: a metaanalysis. Am J Obstet Gynecol. 2009;200:290.e1-9.
6. Yu X, Bao Z, Zou J, Dong J. Coffee consumption and risk of cancers: a meta-analysis of cohort studies. BMC Cancer. 2011;11:96.