Drinking coffee has become very popular over the last 20 years with the health benefits or harms often debated. Caffeine is the active ingredient that gives coffee its taste and you the buzz.
Caffeine is also found in other popular drinks and foods including energy drinks, soft drinks, chocolate, tea, kola nuts, and certain medicines.
It's known as a stimulant as it excites the brain and nervous system. This is why it's used for the short-term relief of fatigue or drowsiness. After drinking caffeine, it usually reaches its peak level in your blood within one hour and stays there for four to six hours.
Caffeine safety
For most people, the amount of caffeine in 2 to 4 cups of coffee a day is not harmful. However, too much caffeine can cause problems, more so in some people than others, such as:
- Poor sleep. If so, avoid coffee or caffeine foods after 4pm or earlier.
- Headaches or dizziness.
- Fast heart beat or cause abnormal heart rhythms.
- Make you jittery, irritable or shaky.
- Heartburn. Caffeine increases the release of acid in your stomach, sometimes leading to an upset stomach or heartburn.
- High blood pressure.
- Anxiety and/or panic attacks can be triggered or made worse by caffeine.
- Dehydration. Caffeine is a diuretic, meaning it makes your body lose more water. So, drinks that contain caffeine are not good if you are thirsty, exercising or working in the heat.
- Tolerance. Needing more and more each day or needing caffeine to 'function' or 'feel normal.'
- Withdrawal symptoms. If you stop using caffeine, you can experience severe headaches, muscle aches, low mood, and irritability.
- Sensitivity reactions. Some people are more sensitive to the effects of caffeine than others.
- Interactions with some medicines. Check with your pharmacist or doctor.
Is caffeine safe for pregnant women?
Most experts feel that using small amounts of caffeine during pregnancy is safe, but larger amounts of caffeine can be harmful during pregnancy. Studies have shown high volumes of coffee in pregnancy, particularly 4 or more cups a day, increases risk of miscarriage. Talk with your doctor about what is safe for you.
Too much caffeine can be very dangerous
Caffeine overdose is dangerous and can kill you. People have died from too much caffeine including a 19-year-old college student who died after taking an overdose of caffeine tablets to stay awake. Also important to note is that caffeine doesn't make a drunk person sober or fit to drive – it does not get rid of the effects of alcohol.
How much caffeine is in our food or drinks?
|
Food |
Caffeine content |
|
Percolated coffee |
60–120mg/250ml cup |
|
Formulated caffeinated beverages or energy drinks |
80mg/250ml can |
|
Instant coffee (1 teaspoon/cup) |
60–80mg/250ml cup |
|
Tea |
10–50mg/250ml cup |
|
Coca Cola |
48.75mg/375ml can |
|
Milk chocolate |
20mg/100g bar |
Table from Food Standards Australia NZ.
Learn more
Freedman, N.D., Park, Y., Abnet, C.C., et al. Association of coffee drinking with total and cause specific mortality New Eng J Med. 366: 1891-904. 2012.
Allan, MG. MD Korownyk C. Mannarino, M. Tools for Practice - Coffee: advice for our vice? Canadian Family Physician. March 2013. Vol 59.26
Caffeine Food Standards Australia NZ
Caffeine Medline Plus
