Ah, yes, coffee. Lifeblood of the modern scholar, soul of the contemporary creative. And I’m sure a few MBAs and other business types partake of it, but I roll mainly with the nerds and the artists, thanks much. Much of sci.casual is written with at least a nearby cup of coffee and something that pairs with the particular cup that I’m drinking. That, or a square or two of dark chocolate, which goes well with most dark roasts of coffee as well as the heart (not a bad way to plug a previous post, yeah?). But now, a study recently published on BMJ Open (which means it’s Open Access – GET YOU SOME SCIENCE NOW but don’t forget to swing by my About page on reading papers if you think you might get intimidated) investigated the association between coffee and liver cancer.
Here’s the thing: liver cancer is a Bad Thing that develops from all sorts of liver conditions, including but not limited to hepatitis. The literature review asserts that incidence is going to continue to rise, and survival rate is still not good. If it’s that hard to fight, we may as well keep it from coming into the gate.
And coffee may be the gatekeeper, our dark knight.
Coffee contains all sorts of stuff that acts as antioxidants, anti-inflammatories, and may even reduce the risk of cancer. Already, there’s been data that shows coffee drinkers have lower risks of chronic liver disease…so why do we need this study again? The thing is about a lot of studies is that they can’t cover everything. You want to think of as many possible variables and relationships that are possible based on previous research, but you can’t know everything. One of the things Kennedy et al. considered in this study is whether all coffee is equal in reducing the risk of liver cancer, particularly good versus useless – I’m sorry, caffeinated versus decaffeinated – coffee. They do cite some studies where even decaf can protect against liver damage, so caffeine may not be liver’s only savior (apart from living well, I guess). There are also other risk factors, such as BMI, existence of hepatitis, and so forth, that need to be dealt with.
This study didn’t require lab rats, actual or human. This kind of study is known as a meta-analysis, and it’s not uncommon in the sciences. In short: the studies are already out there, the results are already out there, could the hypothesis hold if we put all of the results together? Would this new result make the conclusion more powerful because the sample has been pooled together and it’s very diverse?
Putting these results together means combing through pages and pages of research papers. Don’t just read the results, one needs to know what variables were tested, what is the demographics of the sample, how the study was carried out, and even what hypotheses and theory were used to guide the research. And that’s when you actually find those papers. Finding papers leads to finding more papers. Papers and papers. Even then, some of these papers have to be excluded because it turns out it didn’t have what you want, but it’s very likely you’ve had to read at least some of it first. One also needs to find some statistical test that’s appropriate for putting all of this data together or to propose models. This is essentially a literature review to the extreme. Good luck.
What did they find from the more than 16 studies that survived the screening process (out of 323 papers that they’ve found – read the article if you want to see how the process went), which had a total sample size of 2,000,000? The authors found “an inverse association between HCC (hepatocellular carcinoma…OK, liver cancer at the cellular level) for an extra two cups of coffee per day…” in most of the studies – the calculated risk was lower for people who drink 2 cups a day. There was no significant relationship between calculated risk and when the study came out, so one way to interpret it is that coffee has always reduced the risk (at least for the time period the papers came out).
junkdecaf? Pooling all results together, it can reduce the risk by 14%. Sure, it’s lower than realcaffinated coffee (27%), but at least those who have caffeine sensitivities can get in on the life-extending party. They can’t assume that coffee consumption causes lower risk of HCC due to several factors, including the fact that not all HCC cases have actually been to hospital, and for all we know, the only cases they have are for people who have been to hospital. This variable could affect the risk, but that variable may not be acting alone; access to health care may also be tied into socioeconomic status, where they are in the world, how far they are from a hospital (or even a coffee shop), and so on. Other variables exist, like what coffee they’ve been drinking, but that’s just something I’m interested in as a budding coffee snob. What we can know for sure from this study is that it backs up a lot of the literature on coffee and liver cancer, including how caffeine can lower the spread of liver cancer cells and how coffee itself can reduce the risk altogether.
I’m in a coffee shop at least once a week, sipping on dark coffee, having a square or two of dark chocolate, and reading for or writing in sci.casual or my actual research. In short, I’m here to make the world a better place while becoming invincible. You’re welcome.
Featured Article: Kennedy OJ, Roderick P, Buhanan R, Fallowfield JA, Hayes PC, Parkes J (2017). Coffee, including caffeinated and decaffeinated coffee, and the risk of hepatocellular carcinoma: a systematic review and dose-response meta-analysis. BMJ Open 7:e013739. DOI: 10.1136/bmjopen-2016-013739.
Featured Image: Public Domain (Author: Edar, 2014)