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Coffee is a commonly consumed beverage because of its caffeine content, which has many different effects on the human body and can impact blood glucose levels 1. However, coffee appears to have different effects on blood glucose in the long term than in the short term, so more research needs to be done to determine the exact relationship between coffee and blood glucose.
Caffeine Content of Coffee
Caffeine stimulates your central nervous systems and other parts of your body, leading to a feeling of increased alertness and energy. The amount of caffeine in an 8-oz. serving of coffee can vary wildly, from 27 to 200 mg. Even coffee from major retailers can vary in its caffeine content; an 8-oz 1. serving of Dunkin' Donuts coffee may contain between 71 and 103 mg of caffeine. Instant coffee often has less caffeine.
- Caffeine stimulates your central nervous systems and other parts of your body, leading to a feeling of increased alertness and energy.
- serving of Dunkin' Donuts coffee may contain between 71 and 103 mg of caffeine.
Short-Term Effects of Caffeine
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In the short term, caffeine can cause an increase in blood glucose levels. Caffeine decreases your body's sensitivity to insulin, a hormone that helps regulate blood glucose levels. By reducing your response to insulin, caffeine causes an increase in blood glucose levels. A study, published in a 2004 issue of "Diabetes Care" found that individuals had higher insulin levels after drinking coffee for four weeks and had higher blood glucose levels after two weeks 2.
- In the short term, caffeine can cause an increase in blood glucose levels.
- By reducing your response to insulin, caffeine causes an increase in blood glucose levels.
Long-Term Effects of Caffeine
Although in the short term caffeine appears to increase blood glucose levels, it may have the opposite effect in the long term. In 2004, "The Journal of the American Medical Association" published a study that examined insulin sensitivity in individuals who were habitual coffee drinkers. This study found that coffee drinkers had increased insulin sensitivity, which suggests that in the long term coffee can decrease blood glucose levels.
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Chronically high blood sugar levels can damage your blood vessels, nerves and retinas. Because it is not clear how coffee drinking affects your blood glucose levels, you should talk to your doctor if you regularly drink coffee, particularly if you have diabetes. Your doctor may recommend testing your blood glucose levels to see if they are too high.
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- MayoClinic.com: Caffeine Content for Coffee, Tea, Soda and More
- "Diabetes Care"; Effects of Coffee Consumption on Fasting Blood Glucose and Insulin Concentrations; Van Dam et al.; 2004
- Coffee, brewed, prepared with tap water. FoodData Central. U.S. Department of Agriculture. Published April 1, 2019.
- Caffiene in coffee. FoodData Central. U.S. Department of Agriculture. Published April 1, 2019.
- McCusker RR, Fuehrlein B, Goldberger BA, Gold MS, Cone EJ. Caffeine content of decaffeinated coffee. J Anal Toxicol. 2006;30(8):611-3. doi:10.1093/jat/30.8.611
- Coffee, instant, reconstituted. FoodData Central. U.S. Department of Agriculture. Published April 1, 2019.
- U.S. Department of Agriculture. Coffee, espresso. FoodData Central. Published April 1, 2019.
- Tea, hot, leaf, black. FoodData Central. U.S. Department of Agriculture. Published April 1, 2019.
- Soft drink, cola. FoodData Central. U.S. Department of Agriculture. Published April 1, 2019.
- US Food & Drug Administration. Spilling the beans: How much caffeine is too much?. Updated December 12, 2018.
- Rogers PJ, Heatherley SV, Mullings EL, Smith JE. Faster but not smarter: Effects of caffeine and caffeine withdrawal on alertness and performance. Psychopharmacology (Berl). 2013;226(2):229-40. doi:10.1007/s00213-012-2889-4
- 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):1891-904. doi:10.1056/NEJMoa1112010
- Voskoboinik A, Kalman JM, Kistler PM. Caffeine and arrhythmias: Time to grind the data. JACC Clin Electrophysiol. 2018;4(4):425-432. doi:10.1016/j.jacep.2018.01.012
- Papakonstantinou E, Kechribari I, Sotirakoglou Κ, et al. Acute effects of coffee consumption on self-reported gastrointestinal symptoms, blood pressure and stress indices in healthy individuals. Nutr J. 2016;15:26. doi:10.1186/s12937-016-0146-0
- The American College of Obstetricians and Gynecologists. Moderate Caffeine Consumption During Pregnancy. Committee Opinion: 462. Published August 2010.
- Drake C, Roehrs T, Shambroom J, Roth T. Caffeine effects on sleep taken 0, 3, or 6 hours before going to bed. J Clin Sleep Med. 2013;9(11):1195-200. doi:10.5664/jcsm.3170
- Alstadhaug KB, Andreou AP. Caffeine and primary (migraine) headaches-friend or foe?. Front Neurol. 2019;10:1275. doi:10.3389/fneur.2019.01275
- Lara DR. Caffeine, mental health, and psychiatric disorders. J Alzheimers Dis. 2010;20 Suppl 1:S239-48. doi:10.3233/jad-2010-1378
- National Institute of Diabetes and Digestive and Kidney Diseases. Eating, diet and nutrition for GER and GERD. Updated November 2014.
- Jiwani AZ, Rhee DJ, Brauner SC, et al. Effects of caffeinated coffee consumption on intraocular pressure, ocular perfusion pressure, and ocular pulse amplitude: A randomized controlled trial. Eye (Lond). 2012;26(8):1122-30. doi:10.1038/eye.2012.113
- Mitchell DC, Knight CA, Hockenberry J, Teplansky R, Hartman TJ. Beverage caffeine intakes in the U.S. Food Chem Toxicol. 2014;63:136-42. doi:10.1016/j.fct.2013.10.042
Adam Cloe has been published in various scientific journals, including the "Journal of Biochemistry." He is currently a pathology resident at the University of Chicago. Cloe holds a Bachelor of Arts in biochemistry from Boston University, a M.D. from the University of Chicago and a Ph.D. in pathology from the University of Chicago.