Coffee is a morning staple for many people; around 64% of adults’ daily caffeine consumption coming from coffee.1 While so many begin their day with a cup of coffee, they may be unaware of the health benefits of their morning cup of coffee.
Coffee and mortality risk
A study 2 published in the American Journal of Clinical Nutrition that included over 90 000 Japanese participants between the ages of 40 and 69 years reported an inverse association between total coffee consumption and mortality from heart disease, cerebrovascular disease, and respiratory disease. That is, increasing amounts of coffee consumption were associated with reduced risks of mortality, up to approximately 3-5 cups per day. These results were seen for both men and women.
Coffee and risk of hepatocellular carcinoma
Another study3investigated the association between coffee or tea consumption and hepatocellular carcinoma. The participants in the study were recruited for the European Prospective Investigation into Cancer and nutrition (‘EPIC’) trial. The study reported that higher levels of coffee and tea consumption were associated with a reduced risk of hepatocellular carcinoma. The associations were seen with caffeinated coffee but were not the same for decaffeinated coffee.
Coffee and circadian rhythm
Your internal clock, or circadian rhythm, is responsible for regulating several physiological processes, including sleep-wakefulness timing. External factors can influence your circadian clock, resulting in shifts of circadian timing. Some of the known influencers of circadian timing include light, physical activity, and certain drugs.
A study4 investigating whether caffeine can affect circadian timing via melatonin signalling compared consumption of caffeine in the evening – three hours before bedtime – compared with exposure to bright light before bedtime, which is known to delay the circadian clock.
The researchers found that caffeine intake three hours prior to bedtime delayed the circadian clock by approximately 40 minutes compared with the control group. Exposure to the bright light delayed circadian clock timing by approximately 85 minutes, while a combination of caffeine and bright light delayed timing by approximately 105 minutes when compared to the control group.
The researchers suggest that the results of this study are important in terms of treating certain sleep-wake disorders. By strategically timing the intake of caffeine, it can be used as a tool to adjust circadian timing. Such adjustment also has the potential to be used to help in adjusting circadian clock timing in response to jet lag when traveling internationally.
Coffee and irregular heart rhythm
Atrial fibrillation is characterized by an irregular heart rhythm (arrhythmia), and is associated with increased risk of stroke, heart failure, dementia, and all-cause mortality. Researchers from the Karolinska Institutet, Stockholm, Sweden, therefore wanted to assess the effect of coffee on atrial fibrillation. The researchers analysed two cohorts of participants, in addition to reviewing the results of already published studies.5
Data from the Cohort of Swedish Men (41 881 participants) and the Swedish Mammography Cohort (34 594 participants) were analysed for coffee intake and atrial fibrillation. In both cohorts the researchers found no link between intake of coffee and atrial fibrillation.
The researchers then analysed all available data from other studies also addressing coffee consumption and atrial fibrillation. Six studies were identified and included in the analysis. The combined analysis also found no associated risk of atrial fibrillation with increased coffee intake.
While the researchers did not find evidence of an increase in risk of atrial fibrillation with increased coffee consumption, they do state that the available data is limited, suggesting that further study is needed.
As always, moderation is key, and more research should be carried out to confirm the health effects associated with drinking coffee.
- Fulgoni III, VL, Keast, DR, Lieberman, HR “Trends in intake and sources of caffeine in the diets of US adults: 2001–2010” Am J Clin Nutr May 2015 vol. 101 no. 5 1081-1087.
- Saito, E, Inoue, M, Sawada, N, Shimazu, T, Yamaji, T, Iwasaki, M, Sasazuki, S, Noda, M, Iso, H, Tsugane, S “Association of coffee intake with total and cause-specific mortality in a Japanese population: the Japan Public Health Center–based Prospective Study” Am J Clin Nutr 2015 101: 5 1029–1037
- Bamia C, Lagiou P, Jenab M, Trichopoulou A, Fedirko V, Aleksandrova K, Pischon T, Overvad K, Olsen A, Tjønneland A, Boutron-Ruault MC, Fagherazzi G, Racine A, Kuhn T, Boeing H, Floegel A, Benetou V, Palli D, Grioni S, Panico S, Tumino R, Vineis P, Bueno-de-Mesquita HB, Dik VK, Bhoo-Pathy N, Uiterwaal CS, Weiderpass E, Lund E, Quirós JR, Zamora-Ros R, Molina-Montes E, Chirlaque MD, Ardanaz E, Dorronsoro M, Lindkvist B, Wallström P, Nilsson LM, Sund M, Khaw KT, Wareham N, Bradbury KE, Travis RC, Ferrari P, Duarte-Salles T, Stepien M, Gunter M, Murphy N, Riboli E, Trichopoulos D. “Coffee, tea and decaffeinated coffee in relation to hepatocellular carcinoma in a European population: multicentre, prospective cohort study.” Int J Cancer. 2015 Apr 15;136(8):1899-908.
- 4. Burke, TM, Markwald, RR, McHill, AW, Chinoy, ED, Snider, JA, Bessman, SC, Jung, CM, O’Neill, JS, Wright, KP. “Effects of caffeine on the human circadian clock in vivo and in vitro” Science Translational Medicine 16 Sep 2015: Vol. 7, Issue 305, pp. 305
- Susanna C. Larsson, Nikola Drca, Mats Jensen-Urstad and Alicja Wolk “Coffee consumption is not associated with increased risk of atrial fibrillation: results from two prospective cohorts and a meta-analysis” BMC Medicine 2015, 13:207
- Image by Christoph from Pixabay