Caffeine is a natural ingredient found in coffee beans, tea leaves, cocoa beans and over 50 other plants. Coffee, tea and fizzy drinks are the most common sources of caffeine in our diet, however it can also be found in some medications like cough syrups. Caffeine is a stimulant, when consumed it causes a feeling of alertness which is why so many of us reach for a coffee first thing in the morning and late afternoon to help wake us up and get over that 3pm slump.
Caffeine inhibits the action of Adenosine in the central nervous system. Adenosine in the brain plays an important role in promoting sleep and regulates our sleep-awake cycle.
Caffeine blocks adenosine receptors, it has the opposite effects on the body, reducing the sedative- like properties of adenosine, making us feel more alert.
Can you have too much caffeine?
Yes, you can, but too much will be varying amounts of caffeine for different people. Some are more sensitive to caffeine whilst others may have built a tolerance to caffeine after drinking it for long periods of time.
Current guidelines state that adults should consume no more than 400mg per day. During pregnancy, caffeine clearance from the mother’s blood slows down. Therefore pregnant and breastfeeding women should aim for no more than 200mg/day. Excessive intake in pregnant women may result in growth restriction, low birth weight babies or premature labour.
Here are a couple of common drinks and the amount of caffeine they contain per cup:
- Tea – 10-50mg
- Green tea – 30-50mg
- Energy drink – 40-250mg
- Single shot espresso – 75-85mg
- Instant coffee – 60-100mg
- Filter coffee (Short/small) – 157mg
- Can of coke – 32-42mg