Coffee, the love of modern society, the elixir that many crave for, the guilty pleasure that gives us that well-deserved boost. Despite our fondness for coffee, this popular beverage has never made it to the menu of a healthy diet plan. Have you ever thought to yourself, why is this so? Is coffee our friend or foe? Imagine yourself sitting in the audience in a debate hall where the coffee lovers and coffee haters vehemently argue their cases. Let the debate resume! (If you haven’t read Part 1 of this debate, please stop here and read Part 1 (here) before continuing.) Judge: Welcome back everyone. Team For-Coffee, please state your case. Team For-Coffee: Yours Honour, let me present one of my strongest pieces of evidence. In 2012, Freedman et all published a large study in the prestigious New England Journal of Medicine <1>, in which they assessed the amount of coffee consumption for the participants at the beginning then followed them up for 14 years. The study found that coffee consumption is associated with a lower rate of death from major diseases such as heart disease, stroke, diabetes and lung conditions. This was after considering other factors such as smoking. This association of coffee with lower rate of death seem to be the strongest in people who do not smoke are in relatively good health. Team Against-Coffee: Let me stop there! I appreciate the findings from this study but after all, it merely shows an association but does not prove that coffee can reduce rate of death. Judge: That is a fair point, but unfortunately the majority of the studies out there on coffee are observation-only studies. There are very few well-designed clinical trials. Team Against-Coffee: Can you tell me what would be the reason for coffee reducing the risk of these chronic diseases? Judge: There is currently no real prove in what exactly in coffee might be associated with these health benefits. But we know that coffee contains more than 1000 bioactive compounds which might be affecting health. One plausible explanation is that compounds such s antioxidants and polyphenols may be at play here<2>. These molecules might be playing a role in reducing the chronic inflammation associated with these chronic diseases. Team For-Coffee: I read your article recently about the importance of gut microbiota. Could coffee affect our microbiota? Judge: Yes. There is evidence from cellular, animal and even human studies that coffee induces changes in the gut microbiota composition in favour of organisms that are associated with anti-obesity and anti-inflammatory effects<3>. Importantly, there are also some evidence that coffee consumption is associated with decreased risks of breast, bowel, womb and prostate cancer <2>. A variety of mechanisms for such association has been proposed. Antioxidant properties of certain compounds are thought to contribute. Furthermore, coffee may be doing more than just playing the antioxidant card. A high intake of caffeine has been associated with increase in the sex hormone binding protein (SHBP), a protein which binds hormones such as testosterone, reducing the freely-roaming testosterone. This reduction of free testosterone may account for the association with reduced risk of breast and womb cancers. Different non-caffeine compounds in coffee may be also acting directly in the bowel by changing gut flora, increasing bowel movement and metabolising cancer-inducing compounds<4><5>. Team Against-Coffee: Enough with the body, let’s move on to the mind. When I have a cup of coffee, I can’t even sleep. How is that good for mental health?
Judge: It is true that caffeine in coffee can increase alertness and in sensitive individuals such as yourself, it can affect sleep. In a small number of people, it could lead to increased anxiety. However, there are many beneficial effects of coffee on mental health. It has been found to increase concentration and improve mood. Long-term consumption of coffee has been found to be associated with reduced risk of developing stroke, cognitive decline, Parkinson’s disease and Alzheimer’s disease<6>. Team Against-Coffee: Right, seems that I’m not winning here. Surely it is not healthy to drink 10 cups of coffee a day! Judge: That is a valid point. How many cups of coffee a day is considered healthy? Well, the trouble is, many studies we talked about didn’t really look at this. Neither did they distinguish between different preparations of coffee. However, amongst the studies that did look into this, some found that the more coffee you drink, the stronger the benefit, whereas others found that the benefit peaks at 4-5 cups of coffee a day. Team For-Coffee: Your Honour, I think it’s time for the verdict! Judge: Before a conclusion to be drawn, I need to reiterate that most of the evidence we looked at are observational studies, albeit with a large number of participants. The few randomized controlled studies (the strongest clinical evidence to prove causality) only looked at simple outcomes such as blood pressure and cholesterol level. Therefore, the health benefit we have examined today are not proven. It is important to bear in mind that coffee, particularly caffeine, is certainly a substance not without risks, particularly in pregnancy. However, given the evidence available to us so far, I am in favour of coffee. So, my dear jury, what do you think? <1> Freedman et al. Association of Coffee Drinking with Total and Cause-Specific Mortality. NEJM <2> Grosso et al. Coffee, Caffeine, and Health Outcomes: An Umbrella Review. Annu. Rev. Nutr. 2017. 37:131–56 <3>Pan et al. Molecular mechanisms of the anti-obesity effect of bioactive compounds in tea and coffee. Food Funct., 2016, 7, 4481 <4> Vitaglione P, Fogliano V, Pellegrini N. 2012. Coffee, colon function and colorectal cancer. Food Funct. 3:916–22 <5> Huber WW, Parzefall W. 2005. Modification of N-acetyltransferases and glutathione S-transferases by coffee components: possible relevance for cancer risk. Methods Enzymol. 401:307–41 <6> Nehlig A. 2016. Effects of coffee/caffeine on brain health and disease: What should I tell my patients? Pract. Neurol. 16:89–95
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