EFSA also advised that single doses of 100mg of caffeine may increase sleep latency and reduce sleep duration in some adult individuals, particularly when consumed close to bedtime4.
It has long been acknowledged that pregnant women should moderate their caffeine intake. EFSA, in its 2015 Scientific Opinion on Caffeine recommends that, in pregnant or lactating women, caffeine intake should be decreased to 200mg per day from all sources4.
Effects of higher intakes of caffeine
As with many elements of our daily diet, over-consumption may in some people lead to unwanted side effects. Most people consume a level of food or drink that they are comfortable with and therefore would not experience such effects. However, those who do not self-moderate their intakes of caffeine, may experience feelings of anxiety, hyper-activity, nervousness and sleep disturbance5,45.
Caffeine decreases the quantity of sleep and mainly the temporal organisation of slow and REM sleep8,9. These effects might be modulated by individual differences in the expression of the gene coding for the adenosine A2A receptor40,46. Caffeine has also been reported to increase anxiety in some individuals and this effect might also be linked to another polymorphism of the A2A receptor gene47. However, caffeine consumption is not significantly affected by its tendency to increase anxiety, in part because substantial tolerance develops to this effect48. The negative effects linked to over-consumption are usually short lived once an individual returns to their regular pattern of consumption48. It is well known that these effects are more marked in some people than in others7,16,17,19.
In most individuals, it seems that the effects of caffeine are utilised consciously or unconsciously in the management of mood state, and the choice of coffee/caffeine is influenced by the interaction between the mood state before the drink and the effects anticipated based on the content of caffeine in the drink49,50 which would hence lead most individuals to moderate and self-control their caffeine intake.