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Caffeine - Damaging your sleep

What is caffeine? It is a stimulant which affects out mental performance, our physical performance and alters our fluid balance. There have been a lot of studies on the effect of caffeine and we know that our tolerance to this ""drug" does improve over time, making research on this drug difficult.

How much is too much? General consensus is that a habitual moderate intake up to 4mg per kg of body weight (230-400mg/day) has no adverse effect on the health of adults. A small amount of evidence has shown up to 600mg/day has been associated with health issues and for those consuming excessively high intakes above 750mg/day, evidence has provided doubts. The difficulty in interpreting evidence is the ability to measure the caffeine intake and also to consider that some individuals develop a tolerance to higher levels of caffeine, adding a confounder to the research. A lot of studies do look at the acute effects of single large doses of caffeine and not long term repeated smaller loads.

Possible effects on health include:-

- Fetal development. Up to 200mg maximum per day is the recommendations for pregnant women. Caffeine can cross the barrier into the placenta and a foetus cannot break caffeine down. Up to 200mg - day is considered safe

- Osteoporosis. Large loads of caffeine are associated with excretion of calcium in urine. Care is recommended if your calcium intake is low and caffeine high

- High Blood Pressure - Some individuals are sensitive to caffeine and it can cause both high blood pressure and elevated heart rates.

But as caffeine is a brain stimulant and helps to prevent sleepiness what does it do to our sleep?

Caffeine is absorbed into the body quite quickly and levels peak within 30 minutes of consumption. Then the body has to process the caffeine and eliminate it and this varies greatly between different people due to age, weight, health of the liver and medications being used. This is why some people drink coffee just before bed, and others cant drink it after lunch.

To avoid caffeine interrupting your sleep, firstly reduce caffeine consumption 1-2 hours before bed. Even one cup of coffee can be the difference between a good night sleep. Add other life stressors into the mix and you have a drug stimulating an already overactive brain. If you find this helps, try to reduce caffeine consumption for 3-4 hours before bed. Note change in sleep quality.

How much caffeine is in our drinks can be difficult to determine as quality of the coffee beans provides a large range of caffeine levels.

As a guide:- mg per serving

Tea from loose tea 250ml cup - 16-91

Tea from teabags 250ml cup - 40-70

Instant Coffee 250ml cup - 52-85

Percolated Coffee 250ml cup 76-157

Decaf Coffee - Less than 2mg per cup

Cola 500ml bottle 16-106

250ml or energy drink 27-87

Chocolate Drink 150ml 1-6

50g Chocolate Bar 5-36


Even switching to a green tea can still provide 30-50mg per cup, with the length of time to brew and type of tea used affecting overall caffeine levels.

A great way to improve sleep and overall levels of fatigue during the day is to eat a good healthy diet with lots of fruit and vegetables and healthy grains, proteins and dairy, get some fresh air and exercise every day and take good care of yourself both physically and mentally, resting when you need it and giving yourself permission to take a back seat from hectic life for a short time each day.

Sometimes having too much coffee or tea is just a habit we have built up over time, we drink when we get up simply because it is what we do. We drink at 11am because it is time for a cuppa, maybe replace every second coffee or tea with a healthier drink, try water, decaffeinated beverages, hot choc, or even just reduce the strength of your ritual brews.

The bonus may be your discover a new healthier habit and you might even find your moods improve as well.


Eyes wide shut: how caffeine can affect your sleep, 12/3/19 JEan Hailes organisation

Thomas B, Bishop J, manual of dietetic practice 4th ed.


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