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Caffeine - managing your intake


We all have days when we are feeling lethargic or we need to concentrate more than we believe that we are able to. On those days it is easy to find yourself reaching for your favourite form of caffeine. This information aims to highlight some of the negative impacts of caffeine, so that you can make an informed decision about your own personal caffeine consumption and can identify alternative strategies for when you need that boost. There is considerable research into the impact of caffeine and yet consensus is yet to be reached about benefits and adverse effects.

What is Caffeine?

It common knowledge that caffeine is a stimulant and one of the world’s most commonly used drugs. It’s available in many forms but is commonly found in drinks and tablets. Caffeine stimulates the central nervous system; it initiates neurotransmitters firing in your brain, causing physiological responses.

The Impact of Caffeine

  • Caffeine is addictive. Prolonged use means a tolerance is developed, meaning higher doses are required to gain the same impact. If you have noticed you get jittery without caffeine you may be experiencing withdrawal. Withdrawal consists of headaches, shivers and anxiety.
  • Does caffeine improve alertness? There is a debate on this. In 2010 one of the largest studies of caffeine [1] found that participants did not experience heightened alertness; furthermore, alertness decreased for those who had high use. Some argue any perceived improvement is due to high use and that caffeine returns you to a baseline [2]. Many studies have demonstrated that within short term there is increased alertness [3], it is often discussed that the benefits of the alertness are diminished by the other side effects of caffeine.
  • Caffeine and sleep It is generally agreed that caffeine reduces the sensations of fatigue. Tiredness is our body’s signal that we need to rest and when the caffeine wears off we may feel exhausted. It is recommended that you do not have caffeine for six hours prior to bed as it will impair restful sleep [4].
  • Caffeine and dehydration Ensuring we are hydrated is important to keep us well and to aid concentration yet caffeine can have dehydrating effects. This can sound counter indicative but caffeine has a diuretic effect in the body, it encourages the production of urine and therefore leads to dehydration. For this reason you should not rely solely on caffeine-based fluids and should ensure regular consumption of other drinks such as water.
  • Depression and anxiety Caffeine replicates some of the physical symptoms of anxiety such as tremors and changes to breathing patterns. Sustained use of caffeine can have an impact on your mood in particular it can increase anxiety and panic attacks [5] and depressive symptoms [6]. If you are using the buzz of caffeine to cope with anxiety it can compound the underlying difficulties.
  • Hypertension (High blood pressure) Hypertension isn’t just something over 65’s experience. An American study in 2011 has shown that 19% of 24-34 year olds have high blood pressure [7]. It has been shown that caffeine increases blood pressure, and that risks go up with consumption [8]. This can raise your risk of heart disease, heart attacks and strokes.
  • Caffeine and pregnancy Consumer Products and the Environment [9] has shown that too much caffeine during pregnancy might result in a baby having a low birth weight, which can increase the risk of some health conditions in later life.
  • Caffeine and alcohol Caffeine alone is said to reduce risk taking in a variety of settings yet it is demonstrated that a combination of caffeine and alcohol can lead to higher chances of taking high risks behaviours [10].
  • Caffeine can be fatal! A fatal dose of caffeine is thought to be around 10g - equivalent to around 75 8oz cups of coffee or 120 cans of red bull consumed within a few hours. Whilst this is an extremely high amount you would need to take, if you have an underlying or unknown health condition it can be considerably less. In Oct 2013 a painter and body builder from the west midlands died after consuming a packet of caffeine mints. Each mint contains about the equivalent to a can of red bull.
Managing your caffeine intake

What is a safe amount of caffeine to drink? There is currently not an agreed census within the UK for an agreed daily intake of caffeine. The EU Scientific Committee on Food (SCF) [11] considered the effects of caffeine intake in 2003 and noted “that a dose of 5mg caffeine per kilogram bodyweight (300mg for a 60kg person) could result in transient behavioural changes, such as increased arousal, irritability, nervousness or anxiety in some people, particularly if they were normally low consumers of caffeine”. Based on this it is assumed that the maximum daily dose per individual should be 300-400mg. The Food Standards agency has recommended that the maximum amount of caffeine for pregnant women is 200mg [12].

As you can see from the below chart, due to variations in drinks such as coffee it is hard to judge how much caffeine a particular drink has. It is also worth remembering that some cold and flu remedies also contain caffeine. (Information gained from a variety of sources including Food standards agency, branded products own websites).

Item per portion

Caffeine Content mg
Red Bull per can 80
Blue bolt per can 250
Jolt, Rockstar and Monster per can 280
Pro plus 1 tablet 50
Espresso 30 ml 40-75
Brewed Coffee 240ml 95-200
Decaffeinated Coffee 240ml 2-12
Black tea 240ml 14-61
Green tea 240ml 24-40
Lipton Iced tea 5-7
Cola / Pepsi drinks per can 25-46
Chocolate 100g 5-50

Hot chocolate



How to withdraw from caffeine and consider alternative choices

  • Consider why you are taking caffeine, is it because you get a headache when you stop? To support you in pulling an all-night prior to that assignment being handed in? Habit? Is it the taste? Once you have paid attention to why you can start to understand what might be healthier alternatives.
  • It is a myth that the longer you are sitting at your desk the more productive your study is. Take regular breaks and during these breaks do not stay sitting at your desk, have a change of environment or do something different such as sport, art, Reduce your intake gradually - bake, a chat with friends or sing along to some music.
  • Drink plenty of water and eat a balanced diet, it’s not only what you eat but when, try to get in a routine with foods, foods with a low glycaemic index (GI) will give you sustained energy throughout the day whilst those with high GI will give you a quick boost but are likely to make you crash after the boost has worn off.
  • If you are the sort of person that needs the adrenaline of a deadline, give yourself nearer deadlines and reward yourself for achieving them.
  • If you are a procrastinator, identify if this impacts on your quality of life. If it does, split the tasks you need to do into manageable chunks, allow yourself fidget breaks, be kind to yourself and reduce the distractions when you are studying.
  • Getting a good night’s sleep and having plenty of exercise are the key things you can do to ensure that you are full of energy.


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[1] Rogers PJ, Hohoff C, Heatherley SV, Mullings EL, Maxfield PJ, Evershed RP, Deckert J, & Nutt DJ (2010). Association of the anxiogenic and alerting effects of caffeine with ADORA2A and ADORA1 polymorphisms and habitual level of caffeine consumption. Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology, 35 (9), 1973-83

[2] James JE, Rogers PJ. Effects of caffeine on performance and mood: withdrawal reversal is the most plausible explanation. Psychopharmacology. 2005;182:1–8.

[3] accessed 12/02/14 Committee on Toxicity of Chemicals in Food, Consumer Products and the Environment: Second draft statement on the interaction of caffeine and alcohol and their combined effects on health and behaviour (2012).

[4] 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):1195-1200.

[5] Lara DR; Caffeine, Mental Health, and Psychiatric Disorders. Journal of Alzheimer’s Disease (2010) 20 (1) 1387-2877

[6] Lucas M, Mirzaei F, Pan A, et al Coffee, caffeine, and risk of depression among women. Arch Intern Med 2011;171:1571-8

[7] Nguyen, Q. C.; Tabor, J. W.; Entzel, P. P.; Lau, Y.; Suchindran, C.; Hussey, J. M.; Halpern, C. T.; Harris, K. M.; & Whitsel, E. A. (2011). Discordance in national estimates of hypertension among young adults. Epidemiology, 22(4), 532-541

[8] Winkelmayer WC, Stampfer MJ, Willet WC, Curhan GC. Habitual caffeine intake and the risk of hypertension in women. JAMA. 2005;294:2330–2335

[9] 11. Fortier I, Marcoux S, Beaulac Baillargeon L. Relation of caffeine intake during pregnancy to intrauterine growth retardation and preterm birth. Am J Epidemiol 1993;137:931-40.

[10] Effects of energy drinks mixed with alcohol on information processing, motor coordination and subjective reports of intoxication.

Marczinski, Cecile A.; Fillmore, Mark T.; Henges, Amy L.; Ramsey, Meagan A.; Young, Chelsea R.

Experimental and Clinical Psychopharmacology, 20(2), Apr 2012, 129-138

[11] Accessed 13/02/14 Food Standards agency

[12] Accessed 11/02/14