When we finally take a big sip of our morning coffee after walking around like a zombie, we don't often think about its caffeine content -- other than the fact it will give us a nice, welcome buzz.
While some caffeine certainly has its benefits, going overboard with coffee, energy drinks, coke and even tea isn't the best idea for our health.
So, how much caffeine is in a cup of coffee, tea, coke or energy drink -- and what's the recommended daily limit of caffeine?
What effect does caffeine have on our bodies?
"Caffeine is what we call a central nervous system 'stimulant'. In fact, it is the world's most widely used stimulant," Alexandra Parker, accredited practising dietitian of The Biting Truth, told HuffPost Australia.
"This means it acts to increase heart rate and blood flow, which temporarily make you feel more alert and energetic."
Due to caffeine's ability to boost energy levels, athletes and gym-goers often use caffeinated drinks to boost performance.
"Caffeine can improve performance in some sports. This is due to the effect it has on the brain -- caffeine is able to act as an adenosine receptor antagonist," Anna Debenham, accredited practising dietitian of The Biting Truth, told HuffPost Australia.
"In short, this means that by blocking the action of adenosine, it can reduce your feelings of fatigue, resulting in a longer period of sustained work."
Some people are more sensitive to caffeine than others and may find it causes restlessness, anxiety, nervousness, insomnia or an stomach upset.
The benefits of (some) caffeine
Not all sources of caffeine are created equal (looking at you, sugary coke and energy drinks). Coffee and tea, however, do provide some health benefits.
"Like tea, coffee is a rich source of antioxidants, which may help with insulin sensitivity and disease prevention," Parker said.
How much caffeine can you have a day?
How much caffeine an individual should or should not consume varies a great deal and is affected by their gender, age, body weight, health conditions and medications.
"Research indicates that for a healthy adult, a moderate caffeine intake (of up to 400mg) poses no health risk, especially if we eat a balanced diet and enjoy regular physical activity," Debenham said.
"Women who are pregnant or who are trying to become pregnant and those who are breastfeeding should talk with their doctors about limiting caffeine use."
And don't forget about foods which contain caffeine, like chocolate or coffee-flavoured treats such as ice cream and energy bars.
What can happen if you consume too much caffeine?
"Up to 400mg of caffeine a day appears to be safe for most healthy adults. That's roughly the amount of caffeine in four cups of brewed coffee," Parker said. "Although caffeine use may be safe for adults, it's not a good idea for children.
"Heavy caffeine use can cause unpleasant side effects including increased anxiety, restlessness, headaches and difficulty sleeping."
Australia has comprehensive regulatory standards when it comes to caffeine in colas and energy drinks, and controls how much caffeine can be added to these drinks.
"In addition to limiting their caffeine content, foods containing added caffeine must have a statement on the label that the product contains caffeine," Debenham said.
This is how much caffeine is in a cup (250ml) of black coffee, latte, energy drink, black tea, green tea and cola:
- Latte: 113-280mg
- Instant coffee with one teaspoon: 60-70mg
- Black tea: 30-50mg
- Green tea: 30-50mg
- Energy drink: 80mg
- Cola: 36-48mg
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