Question: is decaff tea and coffee better for the brain to sleep than caffeine?

Rachel Sharman answered on 6 Nov 2018:

Hi,

Fantastic question. The thing is, even decaff tea/coffee contains some caffeine.

As we are awake we have a build up of a protein called adenosine in the brain (it is broken down and cleared away as we sleep). It is this build up of adenosine that tells us we are sleepy. Caffeine blocks the brain from seeing the amount of adenosine in the brain. The adenosine is still there, we just don’t respond to it, which is how we get the caffeine crash tiredness when the effect of the caffeine has worn off. Caffeine makes us feel alert, can make us take longer to fall asleep, and can cause sleep to be broken up with lots of little awakenings.

Caffeine is a drug and needs to be used sensibly. The caffeine limit for adults is between 300 and 400mg. Its around 100mg for a teenager. One cup of coffee is around 60-100mg. Decaff coffee is around 20mg. Chocolate contains caffeine and the average small bar is 3mg.

With the teenagers on my study we tell them to be careful of caffeine use, stick to no more than 100mg a day, and try not to consume any caffeinated things after about 6pm. This is because the half life of caffeine (the time it remains active in your body) is around 5 hours so that coffee at 6pm may still be having an impact on your brain at 11pm!