Disclosures: We love coffee.
With our bias thus aired, let’s look at the literature pertaining to coffee and health. This article may seem like a post-hoc rationalization for our continued consumption of this most wondrous of beverages, but there is a large body of evidence that supports a positive association between good health and coffee consumption. Lastly, it is not our intention to persuade, advise, or otherwise influence coffee or caffeine consumption patterns in our readers.
The earliest historical evidence of coffee cultivation and consumption dates back to mid-1400s Yemen.1 Coffee was slow to catch on in what is now the United States until the Revolutionary War. The wartime breakdown of trade relations between Britain and the colonies together with a patriotic aversion to tea following the Boston Tea Party led to a dramatic reduction in colonial tea consumption. Coffee quickly filled the warm beverage vacuum and America’s love affair with coffee began.2 Now for every 3 liters of tap water consumed in modern-day Europe and North America we drink 1 liter of coffee.3
Caffeine is the primary psychoactive component of coffee, acting as a competitive antagonist at the adenosine receptor.4,5 Caffeine’s antagonism of the adenosine receptors causes subsequent release of dopamine, norepinephrine, and glutamate in the brain.4 Other mechanisms including mobilization of intracellular calcium and inhibition of phosphodiesterases are thought to be clinically insignificant at dietary levels of caffeine consumption and will not be considered in today’s discussion.4,5
Caffeine reaches peak levels around 45 minutes after ingestion.4 Caffeine has an average elimination half-life of about 6 hours,4 meaning that your double shot Americano at 8:00 in the morning is metabolized to a single shot by 2:00 in the afternoon. And today’s 8:00 a.m. double shot Americano won’t be fully eliminated from your body until tomorrow afternoon.
Although caffeine is only one of many bioactive compounds contained within coffee, it is the most readily quantifiable and helps to provide equivalent units between different types of coffee. Twelve ounces of brewed coffee contains approximately 200mg of caffeine, while a shot of espresso contains about 65mg of caffeine, or about 33% the caffeine content of a 12-oz brew.6 Importantly, the difference in content is primarily due to the grams of coffee contained in a brew and not the volume of liquid.
It was long assumed that coffee and its stimulant-laced dregs were bad for the heart. Evidence is conflicting, but coffee has been associated with possible increases in “bad” cholesterol7 while caffeine specifically has been associated with transient increases in blood pressure7 and insulin resistance.8 However, individuals appear to develop tolerance to a number caffeine’s ill-effects with habitual use and actually demonstrate improved insulin sensitivity as a net result of other bioactive chemicals in coffee.9
Research often cites the number of “cups” of coffee consumed. A cup is equal to eight ounces, but the volume we are likely most familiar with in the modern coffee consumption environment is the “small,” Starbucks “tall,” 12-oz size. For familiarity and to avoid the redundancy of excessive verbiage, we will refer to 12-oz sized units of coffee as “mugs.”
Now for the research:
In a study of more than 400,000 participants in the NIH-AARP Diet and Health Study published in the New England Journal of Medicine in 2012 Freedman et al.7 found that consumption of ≥4 mugs of coffee per day was associated with a mortality rate reduction of 10% in males and 15% in females when compared to non-coffee drinkers. Interestingly, this mortality reduction association was stable even in those who consumed decaffeinated coffee,7 suggesting that other bioactive chemicals may be responsible for any health benefits attributable to coffee consumption.
Freedman et al.’s findings wet the scientific community’s appetite for coffee research and multiple subsequent papers examined the association still further. In a 2014 meta-analysis that included almost 1 million participants Crippa et al.8 found that coffee drinkers who consumed 2.67 mugs per day had a 16% reduction in all-cause mortality and those who consumed 2 mugs per day appreciated a 21% reduction in mortality attributable to cardiovascular disease. There was no further benefit for quantities above 2.67 mugs and 2 mugs respectively.8
Crippa et al.’s findings regarding the negative correlation between all-cause mortality and coffee consumption were replicated in two additional meta-analyses of similar data sets as well as in a number of prospective studies.9–11 And Crippa et al.’s findings related to coffee’s negative correlation with cardiovascular disease were replicated in a systematic review and meta-analysis of over 1.25 million participants published in the journal Circulation in 2014.12 Significantly, heavy coffee consumption of >4 mugs per day was not associated with an increased risk of cardiovascular disease in the Circulation article.
Additional epidemiological studies have shown negative correlations between coffee consumption and suicide, Parkinson’s disease, Alzheimer’s disease, type 2 diabetes, gallstones, and inflammatory markers.8,13 Furthermore, a recent study by Liu et al.14 suggested that there may be a dose-response negative correlation between melanoma and caffeinated coffee consumption. Liu et al. found that 4 mugs of coffee per day was associated with a 25% reduction in melanoma risk compared with the lowest quantity of intake.14
What could explain these correlations?
Unfortunately, there are as many as 1,000 compounds found in coffee that could mediate the health effects associated with consumption.7 At this time, phenolic antioxidant bioactive compounds are theorized to be the chief mediators of the health benefits of coffee, but much is still unknown.8
We must acknowledge that there are researchers who justifiably question the validity of a largely observational body of research; association, after all, does not imply causation. Others have argued that, if anything, coffee consumption has a net neutral impact on health.15,16 We prefaced this article with the tongue-in-check disclaimer that the review may appear to be a post-hoc rationalization for our love of coffee; however, we disclaimed mostly in jest and believe that an earnest assessment of the literature places the preponderance of evidence firmly in the pro-coffee camp.
It appears that 2-4 mugs of coffee per day may be associated with as much as a 15% reduction in all-cause mortality and a 20% reduction in mortality from cardiovascular disease. There is some data to suggest that the aforementioned associations may also hold true for decaffeinated coffee as well. The studies have yet to separate consumption by brew techniques (boil, espresso, cold brew, etc.).
We want to do a lot of stuff; we’re not in great shape. We didn’t get a good night’s sleep. We’re a little depressed. Coffee solves all these problems in one delightful little cup.
- Weinberg BA, Bealer BK. The World of Caffeine: The Science and Culture of the World’s Most Popular Drug. New York: Routledge; 2001.
- Pendergrast M. Uncommon Grounds: The History of Coffee and How It Transformed Our World. New York: Texere; 2001.
- Food & Agricultural Organization of the United Nations. Medium-Term Prospects for Major Agricultural Commodity Markets. http://www.fao.org/docrep/006/y5143e/y5143e0v.htm. Accessed October 23, 2016.
- Cappelletti S, Daria P, Sani G, Aromatario M. Caffeine: Cognitive and Physical Performance Enhancer or Psychoactive Drug? Curr Neuropharmacol. 2015;13(1):71-88. doi:10.2174/1570159X13666141210215655.
- Nehlig A, Daval J-L, Debry G. Caffeine and the central nervous system: mechanisms of action, biochemical, metabolic and psychostimulant effects. Brain Res Rev. 1992;17(2):139-170. doi:10.1016/0165-0173(92)90012-B.
- Harris R Lieberman, PhD, Bryan Bordeaux, DO, MPH. Benefits and risks of caffeine and caffeinated beverages. UpToDate. https://www.uptodate.com/contents/benefits-and-risks-of-caffeine-and-caffeinated-beverages?source=search_result&search=caffeine&selectedTitle=5~150#H27494889. Accessed October 25, 2016.
- Freedman ND, Park Y, Abnet CC, Hollenbeck AR, Sinha R. Association of coffee drinking with total and cause-specific mortality. N Engl J Med. 2012;366(20):1891-1904. doi:10.1056/NEJMoa1112010.
- Crippa A, Discacciati A, Larsson SC, Wolk A, Orsini N. Coffee Consumption and Mortality From All Causes, Cardiovascular Disease, and Cancer: A Dose-Response Meta-Analysis. Am J Epidemiol. 2014;180(8):763-775. doi:10.1093/aje/kwu194.
- Je Y, Giovannucci E. Coffee consumption and total mortality: a meta-analysis of twenty prospective cohort studies. Br J Nutr. 2014;111(7):1162-1173. doi:10.1017/S0007114513003814.
- Ding M, Satija A, Bhupathiraju SN, et al. Association of Coffee Consumption With Total and Cause-Specific Mortality in 3 Large Prospective Cohorts. Circulation. 2015;132(24):2305-2315. doi:10.1161/CIRCULATIONAHA.115.017341.
- Zhao Y, Wu K, Zheng J, Zuo R, Li D. Association of coffee drinking with all-cause mortality: a systematic review and meta-analysis. Public Health Nutr. 2015;18(7):1282-1291. doi:10.1017/S1368980014001438.
- Ding M, Bhupathiraju SN, Satija A, van Dam RM, Hu FB. Long-term coffee consumption and risk of cardiovascular disease: a systematic review and a dose-response meta-analysis of prospective cohort studies. Circulation. 2014;129(6):643-659. doi:10.1161/CIRCULATIONAHA.113.005925.
- Ding M, Bhupathiraju SN, Chen M, van Dam RM, Hu FB. Caffeinated and decaffeinated coffee consumption and risk of type 2 diabetes: a systematic review and a dose-response meta-analysis. Diabetes Care. 2014;37(2):569-586. doi:10.2337/dc13-1203.
- Liu J, Shen B, Shi M, Cai J. Higher Caffeinated Coffee Intake Is Associated with Reduced Malignant Melanoma Risk: A Meta-Analysis Study. PloS One. 2016;11(1):e0147056. doi:10.1371/journal.pone.0147056.
- O’Keefe JH, Bhatti SK, Patil HR, DiNicolantonio JJ, Lucan SC, Lavie CJ. Effects of Habitual Coffee Consumption on Cardiometabolic Disease, Cardiovascular Health, and All-Cause Mortality. J Am Coll Cardiol. 2013;62(12):1043-1051. doi:10.1016/j.jacc.2013.06.035.
- Ivanov A, Patel T, Ho J, et al. Effect of Coffee or Tea Consumption on Mortality and Morbidity: A Network Meta-Analysis of 58 Studies. J Am Coll Cardiol. 2016;67(13):1919. doi:10.1016/S0735-1097(16)31920-9.