Caffeine FAQs

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What are the sources of caffeine in the diet?

Caffeine occurs in some 60 plant species including cocoa, maté, guarana, tea and coffee. As such you will find it naturally occurring in products such as coffee, tea and chocolate. Other sources of caffeine include yerba maté and guarana berries. It is also used as an addition in some foods, soft drinks and medicines.

How much caffeine is found in popular food and beverages?

A typically cup of black coffee contains 85mg of caffeine; however the exact amount will vary depending on brewing method, strength of brew, cup size and type of coffee bean.   A cup of tea typically provides 20-45mg caffeine, a can of cola type beverage 30 – 48 mg and a 30g serving of dark chocolate 20-120mg1,2,3.

What is the main effect of caffeine on the body?

The main effect of caffeine is as a mild central nervous system stimulant. The European Food Safety Authority concluded that 75mg of caffeine, the amount found in a regular cup of coffee, increases both selective attention (focusing on the relevant stimulus) and sustained attention (the maintenance of focused attention over an extended period of time)4.  Higher caffeine intakes, such as those found in more than one or two cups of coffee, do not necessarily result in additional increases in alertness or mental performance.

Does caffeine play a role in physical performance?

The European Food Safety Authority has also recognised a cause and effect relationship for caffeine intake and increased endurance performance, endurance capacity and a reduction in perceived exertion5.  The effects of caffeine on short-term high intensity exercise remains inconclusive.

What role does caffeine play in neurodegenerative conditions?

Epidemiological studies suggest that regular, lifelong, moderate consumption of caffeinated coffee may slow down physiological, age-related cognitive decline, especially in women and those over 80 years old in particular.

In addition to this, research suggests that there is a protective association between lifelong coffee consumption and risk of developing Alzheimer’s Disease, however further large scale studies are required to draw firm conclusions. Epidemiological studies also suggest that caffeine reduces, or delays the development of Parkinson’s Disease.

What are the mechanisms for the role caffeine appears to play in neurodegenerative conditions?

With regard to Alzheimer’s Disease, studies suggest that it is likely that caffeine plays a key role, however further research is required to fully understand the mechanism.  In Parkinson’s disease, current thinking suggests that caffeine plays a role by blocking two adenosine receptors in the brain, A2A and A1, which may improve locomotion.  However, effects of other coffee components on the brain have also been identified.

Does caffeine cause sleep problems?

Caffeine intake may affect sleep patterns in some individuals, causing prolonged sleep latency, shorter total and deep sleep time and more frequent awakenings. The effects of caffeine on sleep are smaller in regular coffee consumers compared to occasional consumers.

Caffeine abstinence may improve sleep, reducing the time taken to fall asleep and improving sleep quality for some. Human sensitivity to the effects of caffeine on sleep is variable and genetic differences are also known to play a role.

Can the stimulatory effect of caffeine intake help to keep individuals awake when sleep deprived?

Yes, the stimulatory effects of caffeine have been shown to be beneficial in situations which require increased alertness, and particularly when arousal levels are low, such as during night shifts, driving long distances, or whilst suffering jet lag.

Does research suggest that individuals can become dependent on caffeine?

Brain mapping technology indicates that caffeine is not linked to the brain circuit of dependence6.  This is supported by the fact that individuals do not develop a tolerance to the stimulant effects of caffeine. The American Psychological Association also does not recognise caffeine as being an addictive substance

What happens when caffeine consumption is stopped?

The American Psychological Association recently added Caffeine Withdrawal as a syndrome to its latest edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM V)7. In the manual, Caffeine Withdrawal is defined as a syndrome resulting from abrupt cessation or reduction in caffeine, following prolonged daily use.

In line with DSM V, previous research suggests that only a subset of the population of caffeine consumers suffers withdrawal symptoms (headache, reduced alertness, and drowsiness) following sudden cessation. In these cases, the symptoms begin about 12-24 hours after cessation and reach a peak after 20-48 hours. Importantly, these symptoms can be avoided altogether if caffeine intake is decreased progressively.

Does caffeine intake increase blood pressure?

Caffeine has a slight, transient hypertensive effect. At low doses, it would be comparable to the transient increase experience during a conversation. However, evidence suggests that regular consumption of coffee, containing caffeine, does not increase the risk of hypertension8.

Is caffeine intake linked to CVD risk factors?

Caffeine is not linked to other CVD risk factors, such as increased cholesterol levels and increased homocysteine levels.

Does caffeine consumption cause dehydration?

Caffeine, as a compound, is a mild diuretic which increases the frequency of urination but not the amount of fluid passed. Tolerance to this effect increases rapidly, so typically this does not affect regular caffeine consumers. Recent studies and literature reviews conclude that moderate caffeine consumption does not lead to dehydration in both regular caffeine consumers and also athletes performing in heat9,10.

Therefore, advice to abstain from drinking moderate amounts of caffeinated coffee, in order to maintain adequate fluid balance, is unfounded.

Is caffeine consumption linked with an increased risk of osteoporosis?

Osteoporosis is a multifactorial condition, affected by diet, calcium intake, sedentary life and genetic factors.

Whilst there is weak evidence to suggest that caffeine intake may be associated with an increased risk of osteoporotic fractures, this has only been observed in women who have not had sufficient calcium in their diet.

Two recent review papers showed differing result, one highlighting that the current data are insufficient to reach any convincing conclusions11, the other suggesting that whilst high consumption of coffee may be associated with a modest decrease in bone mineral density12, there was no evidence of a substantially increased incidence of osteoporosis or fractures typically associated with osteoporosis.  Clearly further research is required to confirm the role of caffeine and coffee in bone mineral density and osteoporosis.

What are the recommendations on caffeine intake for the general population?

In Europe,  the European Food Safety Authority (EFSA) advise that daily caffeine intakes up to 400mg and single doses up to 200mg do not raise concerns13.

What happens with higher caffeine intakes?

Most people consume a level of caffeine that they are comfortable with, however, for some people drinking more coffee than they are used to may lead to hyperactivity or sleep disturbance. These effects are usually short lived once the individual returns to their regular pattern of consumption. It is well known that these effects are more marked in some people than in others.  Caffeine intake in moderation does not cause any problems for the majority of people.

Should pregnant women limit their caffeine intake?

There are specific recommendations for pregnant women who typically metabolise caffeine at a slower rate, advising upper levels of 200 mg caffeine per day from all sources13. In those who are breastfeeding caffeine intakes of 200mg per day do not raise safety concerns13.



  1. Illy A. et al. (1995) Espresso Coffee. The chemistry of quality. Academic Press, London.
  2. Harland B.F. (2000) Caffeine and nutrition. Nutrition, 7/8: 522-526.
  3. Heckman M.A. et al. (2010) Caffeine (1, 3, 7-trimethylxanthine) in foods: a comprehensive review on consumption, functionality, safety, and regulatory matters. J Food Sci, 75: R77-87.
  4. EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA) (2011) Scientific Opinion on the substantiation of health claims related to caffeine and increased fat oxidation leading to a reduction in body fat mass (ID 735, 1484), increased energy expenditure leading to a reduction in body weight (ID 1487), increased alertness (ID 736, 1101, 1187, 1485, 1491, 2063, 2103) and increased attention (ID 736, 1485, 1491, 2375) pursuant to Article 13(1) of Regulation (EC) No 1924/20061. EFSA Journal; 9(4): 2054.
  5. EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA) (2011) Scientific Opinion on the substantiation of health claims related to caffeine and increase in physical performance during short-term high-intensity exercise (ID 737, 1486, 1489), increase in endurance performance (ID 737, 1486), increase in endurance capacity (ID 1488) and reduction in the rated perceived exertion/effort during exercise (ID 1488, 1490) pursuant to Article 13(1) of Regulation (EC) No 1924/2006. EFSA Journal; 9(4): 2053 [24 pp.]. doi:10.2903/j.efsa.2011.2053
  6. Nehlig A. (1999) Are we dependent upon coffee and caffeine? A review on human and animal data. Neurosci Biobehav Rev, 23(4): 563-76.
  7. American Psychiatric Association (2013) Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM V) ISBN 978-0-89042-554-1DSMV.
  8. Geleijnse J.M. (2008) Habitual coffee consumption and blood pressure: an epidemiological perspective. Vasc Health Risk Manag, 4(5): 963-70.
  9. Ruxton C.H.S. (2008) The impact of caffeine on mood, cognitive function, performance and hydration: a review of benefits and risks. Nutr Bull, 33: 15–25.
  10. Armstrong L.E. et al. (2007) Caffeine, fluid-electrolyte balance, temperature regulation, and exercise-heat tolerance. Exerc Sport Sci Rev, 35(3): 135-40.
  11. Liu H. et al. (2012) Coffee consumption and risk of fractures: a meta-analysis. Arch Med Sci, 8(5):776-83.
  12. Hallström H. et al. (2013) Long-term coffee consumption in relation to fracture risk and bone mineral density in women. Am J Epidemiol, 178(6): 898-909.
  13. EFSA, (2015) Scientific Opinion on the Safety of Caffeine, EFSA Journal, 13(5):4102.


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