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Coffee & Health
Mental performance

Coffee and fatigue

Fatigue or tiredness is described as a lack of, or decreased, energy, and physical or mental exhaustion.

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Mental performance
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Effects of coffee consumption

It is suggested that at any given time, 1 in 5 people feel unusually tired and 1 in 10 have prolonged fatigue93; and it is reported that 5-7% of encounters with a doctor are fatigue related94.

A reduced level of concentration, associated with fatigue, has the potential to cause issues in everyday life. In this topic we consider the broad role of coffee in addressing fatigue.

Coffee, caffeine and alertness

Coffee drinking is associated with feelings of alertness1 and has a role in counteracting some of the symptoms of fatigue95.

The main active component in coffee is caffeine, a natural compound found in a number of plant species including coffee, tea and cocoa96. A typical cup of coffee contains 75-100mg caffeine, whilst levels in brewed tea and cocoa are lower96,97,98. The European Food Safety Authority (EFSA) has concluded that a cause and effect relationship has been established between a 75mg serving of caffeine – the amount found in approximately one regular cup of coffee – and both increased attention (concentration) and alertness, mainly in situations of low arousal1.

The role of caffeine in increasing alertness is described here.

Research has suggested that the consumption of 100mg caffeine leads to higher ratings of alertness and overall mood and lower mental fatigue ratings95. Tiredness and headache ratings were also lower following regular coffee compared to placebo and decaffeinated coffee95.

Coffee caffeine and fatigue in daily life

There are a number of circumstances in daily life when caffeine consumption may help to improve feelings of alertness, such as driver fatigue, coping with jet lag and general alertness for instance in the workplace15,58,99. The effects of caffeine on alertness are often clearest in situations where an individual’s fatigue is increased and alertness reduced, such as when suffering from the common cold100, or working at night15.

Night work

Fatigue is a potential issue for those who work night shifts. During night work, caffeine has been shown to reduce cognitive failures and accidents by about half in subjects consuming over 220mg caffeine daily15.

In some individuals sleep may be affected by caffeine consumption, and there is an association between a daily intake of caffeine, reduced sleep quality, and increased daytime sleepiness35,36. A review of research on coffee, caffeine and sleep suggested that individuals respond differently to caffeine based on a variety of factors, including age, sensitivity levels, regular coffee and caffeine intake, time of consumption and genetic variability36.  Individuals who find that caffeine affects their sleep are advised to avoid it in the hours before bedtime.

Further information on coffee and sleep can be found here.

Jet lag

Jet lag may be experienced after a long haul flight across different time zones and can cause extreme sleepiness or wakefulness at inappropriate hours. To counter jet lag, it helps to adjust to the new time zone quickly, sleeping, waking and eating at times appropriate to that area85,101,102.

Coffee consumption is associated with increased alertness1 and may help to manage fatigue in those who experience jet lag85,101,102, further information is available here.

Driver fatigue

Driver fatigue is an issue that can affect all drivers. Fatigue and sleepiness reduce reaction time, vigilance, alertness and concentration so that the ability to perform attention-based activities, such as driving, is impaired. The speed at which information is processed is also reduced by sleepiness and the quality of decision-making may also be affected103.

Research by the European Commission has found that a person who drives after being awake for 17 hours doubles their risk of crashing104. Despite this, 23% of drivers say they have felt extreme fatigue whilst driving and 3% have fallen asleep at the wheel104.

Research suggests that drinking strong coffee containing 150-200mg caffeine together with a short nap is effective at reducing driver sleepiness18,20.

Fatigue is also an issue in those who drive commercial vehicles. Research in long distance lorry drivers suggests that 43% of drivers reported consuming caffeinated drinks, such as coffee, tea, and energy drinks or taking caffeine tablets, to stay awake22. After adjusting for confounding factors, including age, sleep patterns, driving distance and number of breaks, drivers who consumed these products for this purpose had a 63% reduced likelihood of crashing22.

Further information can be found here.

Caffeine and fatigue in sports performance

Research suggests that caffeine may help to improve physical performance during both endurance and high-intensity exercise105, 106, 107. The European Food Safety Authority (EFSA) concluded that there is an association between caffeine consumption and an increase in endurance performance, endurance capacity and a reduction in the rated perceived effort or exertion during exercise108.

A detailed overview of the role of caffeine in sports performance and fatigue can be found here.

Although much of the research has been undertaken in trained athletes, studies in sedentary people and those with lower levels of fitness also suggest that caffeine can improve performance in those who are not trained athletes109,110.

Hydration and fatigue

Fatigue is also closely linked with levels of hydration. Research suggests that consistent effects of mild dehydration include confusion, anger and fatigue111.

Fluid in the body is important: EFSA has concluded that a cause and effect relationship has been established between the dietary intake of water and the maintenance of normal and physical cognitive function112. Whilst there is some indication of a short-term diuretic effect of caffeine intake, this effect does not counter-balance the effects of the fluid intake from coffee drinking113-118. Drinking caffeinated coffee in moderation can help to maintain adequate fluid balance113-118.

Further information on fluid balance can be found here.

Coffee and caffeine intakes

A moderate intake of coffee (3-5 cups per day), spread appropriately throughout the day to suit the lifestyle of an individual can help to address feelings of fatigue in everyday situations including alertness in the workplace or whilst driving. Those who are sensitive to caffeine and find it affects their sleep patterns can avoid caffeine and coffee in the hours before sleep.

The European Food Safety Authority (EFSA) in a review on the Safety of Caffeine concluded that a moderate caffeine consumption, of up to 400mg caffeine per day (the equivalent of up to 5 cups of coffee), can be enjoyed as part of a healthy balanced diet and an active lifestyle119. Pregnant and breastfeeding women are advised to limit their caffeine intake to 200mg per day119.

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