March is caffeine awareness month. Coffee is one of the commonest forms in which caffeine is consumed daily. In the UK alone, it is estimated that nearly 100 million cups of coffee are consumed per day. Despite coffee’s popularity, there remains much conflicting scientific evidence regarding the benefits and potential downsides of drinking coffee, and the impact of caffeine on brain health.
Caffeine is a psychoactive substance, which may increase alertness and arousal, and therefore enhance cognitive performance. Long term coffee consumption across the lifespan has been associated with a decreased risk of developing Alzheimer’s disease and Parkinson’s disease. These findings may be explained by some of the phytochemicals present in coffee, which may exert protective effects.
Coffee has been indicated to modulate dopamine-mediated responses related to cognition and movement, which may have some preventative and ameliorative effects in Parkinson’s disease. In Alzheimer’s, coffee has been suggested to decrease the accumulation of beta-amyloid, a key marker of Alzheimer’s, when >2 cups per day were consumed. However, positive results with respect to coffee and Alzheimer’s risk reduction specifically have not been observed consistently across studies, and therefore further research is merited. Additionally, caffeine consumption may disrupt sleep, depending on the time of day that it is consumed. This could theoretically increase risk of Alzheimer’s disease development long term as sleep is essential for the functioning of the glymphatic system, which is involved in beta amyloid clearance.
Daily consumption of caffeine over 600 mg could have a detrimental impact on the heart-brain axis, via increasing serum homocysteine and cholesterol levels. Furthermore, higher intakes of caffeine have also been suggested to increase anxiety, restlessness and cause gastrointestinal disturbances.
Caffeine increases levels of dopamine, a neurotransmitter, involved in experiencing pleasure, and also involved in the biology of addiction. Addiction to coffee, and therefore caffeine, is prevalent, and can manifest with a variety of withdrawal symptoms, including headaches, tiredness and irritability. Coffee should therefore be enjoyed in moderation, at no more than 200 mg in one sitting (around 2½ cups of coffee) or 400 mg overall daily (which equates to 5 cups of coffee).
Current NHS guidelines suggest that no more than 200mg of caffeine should be consumed daily during pregnancy. Notably, the British Medical Journal has recently challenged this view based on findings from observational studies, which suggest that caffeine should be avoided completely whilst trying to conceive and during pregnancy, as it may increase incidences of miscarriage, stillbirth and adverse pregnancy outcomes.
In conclusion, individuals should moderate their consumption of coffee, and caffeine. If sensitive to the effects of caffeine, trying to become pregnant, or pregnant, individuals should consider caffeine free alternatives to coffee. A further caveat specifically for pregnancy is that some caffeine free herbal teas should only be consumed in small amounts, and some must be avoided completely, in pregnancy, and the advice of a midwife or physician should be sought if needed.