Coffee beans

Nutrition & Health Info Sheets for Health Professionals - Caffeine

Nutrition & Health Info Sheets contain up-to-date information about nutrition, health, and food. They are provided in two different formats for consumer and professional users. These resources are produced by Dr. Rachel Scherr and her research staff. Produced by Taylor Berggren, MS, Dan Buettner, BS, Kaitlyn Grim, BS, Ganesh Jialal, BS, Anna Jones, PhD, Rachel E. Scherr, PhD, Sheri Zidenberg-Cherr, PhD, Center for Nutrition in Schools, Department of Nutrition, University of California, Davis, 2018.

What is caffeine?

Caffeine is a bitter substance found in a variety of food products, including coffee, tea, soft drinks, energy beverages, chocolate, and certain medications (1). Caffeine is currently the most consumed psychoactive drug (2); over 90% of adults in the US consume caffeine daily (3). Caffeine is found naturally in the leaves and seeds of various plants throughout South America and Asia, but it is also a common additive in foods and beverages (2,3). Coffee is a common dietary source of caffeine worldwide (3). The caffeine is found in the coffee bean of the Arabica or Robusta plants (4).

What are common dietary sources of caffeine?

Caffeine is found naturally in coffee beans, tea leaves, kola nuts, and cacao pods (1). In addition to natural caffeine, there is synthetic caffeine that is used in medications, and some foods and drinks. This includes energy beverages and certain gums and snacks (1).

Much of the caffeine consumed is through drinks. One eight-ounce cup of coffee can contain 95 to 200mg of caffeine (1).

Table 1: Dietary sources of caffeine (5,6)
Item Size (fluid oz, unless noted) Caffeine content (mg)
Brewed coffee 8 95-165
Brewed coffee, decaf 8 2-5
Espresso 1 47-64
Instant coffee 8 63
Latte or mocha 8 63-126
Brewed black tea 8 25-48
Brewed green tea 8 25-29
Cola 12 34
Diet Cola 12 46
Energy drinks 16 160-357
Energy shots 2 200
Coffee-flavored yogurt 6 (oz by weight) 30
Coffee ice cream 4 (oz by weight) 11-125
Hot chocolate 16 25
Milk chocolate bar 1.6 (oz by weight) 9

How much caffeine is safe to consume?

Over 95% of adults in the United States consume caffeine through foods and/or beverages; 70-90% of this total caffeine consumption comes from coffee and tea. For most population groups, the average daily intake falls below what is considered moderate caffeine intake (a maximum of 400 mg caffeine per day). There are, however, some groups that exceed this upper limit including men aged 31 to 70, and women 31 years and older (7). In general, it is not harmful to consume up to 400mg of caffeine per day for adults, though sensitivity to caffeine varies greatly (1).

Because of the systemic effects of caffeine, there are certain groups of people that should limit or completely avoid consumption. These groups include (1):

  • pregnant or breastfeeding women
  • children
  • teenagers
  • those with sleep disorders
  • those with migraines or other chronic headaches
  • those with anxiety
  • those with reflux or ulcers
  • those with heart irregularities or arrhythmias
  • those who have or have had high blood pressure
  • those taking certain medications or supplements

What are the effects of caffeine supplementation on health?

Caffeine levels in the blood peak within one hour of caffeine consumption; the effects may persist for up to four to six hours (1,3).

  • Neurological effects: Caffeine stimulates the central nervous system resulting in a feeling of alertness or increased energy (1). Research suggests that caffeine consumption has positive effects on the brain; one study found that 200mg of caffeine each day may boost long-term memory (3). In rats, caffeine was shown to improve memory retention when administered in moderate doses after a training activity and to improve memory retrieval when provided prior to training (8).
    A study from the Harvard School of Public Health suggests that drinking between two and four cups of coffee each day may decrease suicide risk in adults (3). Some studies show that caffeine may be effective in the treatment of some types of headache (2,9).
    In children, caffeine consumption may alter food and beverage preferences later in life by affecting the developing brain. Specifically, the reward-and-addiction center of the brain may be affected in a gender-specific manner (10).
  • Metabolic effects: When consumed, caffeine acts as a stimulant to the central nervous system causing a variety of effects on the body that range from increased alertness and feeling more awake to bouts of agitation and heartburn (1). Additionally, caffeine can relax smooth muscle, stimulate cardiac muscle, and act as a mild diuretic, increasing urination, in some people (2). This diuresis has not been associated with dehydration (11). Caffeine may affect the amount of stomach acid released, potentially causing heartburn, and may also interfere with calcium absorption (1). Caffeine also increases blood pressure (1).
  • Effects of caffeine on sleep: In studies of restricted sleep, caffeine-containing gum has been shown to increase response speed, improve detection of events, and maintain overall cognitive function (12). Caffeine may delay or prevent sleep or improve performance in situations of sleep deprivation; however, these results vary greatly from person to person (3).

What are the effects of cutting back on caffeine?

Abruptly eliminating caffeine intake after consumption on a regular basis may lead to caffeine withdrawal; symptoms of withdrawal include headaches, drowsiness, irritability, nausea, depression, anxiety and difficulty concentrating (1,3,9). Slowly reducing the amount of caffeine consumed over time can help mitigate these effects. Habitual consumption has also been linked to headaches and migraines (9).

Does caffeine improve physical performance?

Caffeine is widely accepted as an effective and safe ergogenic aid. Research, though, is conflicting when examining at the effects of caffeine on physical performance. Ingestion of caffeine has been shown to markedly improve triathlon performance by reducing swim time and time to completion (13). Caffeine has also been shown to reduce perceived measures of fatigue (14). In runners, coffee ingestion was shown to enhance race performance in comparison to placebo (15). In experienced basketball players, caffeine consumption was also shown to enhance performance (16). Caffeine does, however, have its limits in improving athletic performance. One study demonstrated that caffeine did not increase measurements of power through vertical jump or non-treadmill sprinting (14). Additionally limiting for interpretation is the potential placebo effect of caffeine. One study showed that both the caffeine and the placebo yielded similar performance outcomes and did not alter VO2 max measurements (17).

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  1. Caffeine: MedlinePlus. MedlinePlus Trusted Health Information for You. Accessed March 14, 2017.
  2. Caffeine. National Center for Biotechnology Information. PubChem Compound Database. Accessed March 14, 2017.
  3. Suhasini.S J, Sethu G. Intake of Caffeine. Journal of Pharmaceutical Sciences and Research. 2015;7(6):355-356.
  4. Griffin M. Arabica and Robusta Coffee Plant. Coffee Research. Accessed March 14, 2017.
  5. Caffeine content for coffee, tea, soda and more. Mayo Clinic. Published April 14, 2017. Accessed March 14, 2017.
  6. Caffeine Chart. Center for Science in the Public Interest. Accessed March 14, 2017.
  7. Chapter 2 Shifts Needed To Align With Healthy Eating Patterns. A Closer Look at Current Intakes and Recommended Shifts - 2015-2020 Dietary Guidelines. Accessed March 14, 2017.
  8. Angelucci M, Cesário C, Hiroi R, Rosalen P, Cunha CD. Effects of caffeine on learning and memory in rats tested in the Morris water maze. Brazilian Journal of Medical and Biological Research. 2002;35(10):1201-1208. doi:10.1590/s0100-879x2002001000013.
  9. Shapiro RE. Caffeine and headaches. Current Pain Headache Reports. 2008;12(4):311-315.
  10. Seifert SM, Schaechter JL, Hoershorin ER, Lipshultz SE. Health Effects of Energy Drinks on Children, Adolescents, and Young Adults. Pediatrics. 2011;127(3):511-528. doi:10.1542/peds.2009-3592.
  11. Zhang Y, Coca A, Casa DJ, Antonio J, Green JM, Bishop PA. Caffeine and diuresis during rest and exercise: A meta-analysis. Journal of Science and Medicine in Sport. 2015;18(5):569-574. doi:10.1016/j.jsams.2014.07.017.
  12. Kamimori GH, Mclellan TM, Tate CM, Voss DM, Niro P, Lieberman HR. Caffeine improves reaction time, vigilance and logical reasoning during extended periods with restricted opportunities for sleep. Psychopharmacology. 2014;232(12):2031-2042. doi:10.1007/s00213-014-3834-5.
  13. Potgieter S, Wright HH, Smith C. Caffeine Improves Triathlon Performance: A Field Study in Males and Females. International Journal of Sport Nutrition and Exercise Metabolism. 2018:1-34. doi:10.1123/ijsnem.2017-0165.
  14. Hahn CJ, Jagim AR, Camic CL, Andre MJ. The acute effects of a caffeine-containing supplement on anaerobic power and subjective measurements of fatigue in recreationally-active males. Journal of Strength and Conditioning Research. 2018:1. doi:10.1519/jsc.0000000000002442.
  15. Clarke ND, Richardson DL, Thie J, Taylor R. Coffee Ingestion Enhances One-Mile Running Race Performance. International Journal of Sports Physiology and Performance. 2017:1-20. doi:10.1123/ijspp.2017-0456.
  16. Puente C, Abián-Vicén J, Salinero J, Lara B, Areces F, Coso JD. Caffeine Improves Basketball Performance in Experienced Basketball Players. Nutrients. 2017;9(9):1033. doi:10.3390/nu9091033.
  17. Brietzke C, Asano RY, Lima FDRD, et al. Caffeine effects on VO2max test outcomes investigated by a placebo perceived-as-caffeine design. Nutrition and Health. 2017;23(4):231-238. doi:10.1177/0260106017723547.

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