Do you need your cup of tea or coffee to get your day started? 

Do you rely on it to perk you up during the day when you are feeling low?

Do you find that if you skipped even one cup it gives you a headache?

Caffeine is found naturally in foods like cacao, coffee, tea, guarana (seeds of a Brazilian plant) and Yerba Mate (South American herb).  It is also contained in soft drinks, chocolate or coffee flavored foods, energy drinks and some pain relievers.  Below are some sources of caffeine and the amounts contained.

Food Serving size Caffeine (mg)
Coffee (instant) 8 ounces 62
Coffee (brewed) 8 ounces 95
Tea (black) 8 ounces 47
Green Tea (brewed) 8 ounces 28
Cola Beverage 16 ounces 44
Chocolate Milk (hot cocoa) 8 ounces 5
Red Bull 8.4 ounces 75
Chocolate cake with frosting 1 piece (138 grams) 8

Source: USDA
How caffeine works?
Caffeine stimulates the central nervous system and is one of the most widely used stimulants. 
The caffeine molecule is similar to the chemical adenosine, which promotes sleep.[1] After caffeine is consumed it binds to the adenosine receptors, so adenosine cannot work and slow down the body.  

Instead caffeine stimulates an increase in dopamine, the feel good neurotransmitter, which explains why we feel awake and energized after drinking it.  [2]

The effect of caffeine on everyone is different and will depend on their sensitivity, sex, age and body mass.  Some people feel fine after 5-6 cups and for others, who are very sensitive to caffeine, they get an irregular heartbeat after a small amount. 
How much caffeine can I have?

Health Canada scientists have reviewed the health effects of caffeine.  Based on their research a moderate daily intake for adults is 400 mg/day (around 4 cups of coffee).

As parents we would never give our young children a cup of coffee, however, for some soft drinks are acceptable.  As seen in the table above one 16 ounce bottle of cola contains their recommended caffeine intake for the day. 

Health Canada recommends the maximum caffeine intake level for children as:

4-6 years old ~ 45 mg/day
7-9 years old ~ 62.5 mg/day
10-12 years old ~ 85 mg/day

Health Canada has not developed any definitive advice for teenagers because of insufficient data.  However, it suggests that daily caffeine intake for this age group to be no more than 2.5 mg/kg body weight.

Health Canada recommends that women who are planning to become pregnant, are pregnant or breastfeeding women restrict their daily caffeine intake to 300 mg/day. 
(Source: Health Canada)

Below I share some of the effects of caffeine:

Caffeine Highs:
Brain Booster: Caffeine has been shown to stimulate alertness, concentration and reduce fatigue. 

Improves Stamina: Athletes often use energy drinks and gel that contain caffeine to improve their training as it enhances endurance and resistance to fatigue. 

Mood Enhancer:  After having some caffeine the mood improves, feeling happier and energised.

Cellulite: In animal studies topical caffeine has been shown to have a therapeutic role in cellulite reduction.  (Green Med Info)

Combination of caffeine with other substances reduces body fat and the caffeine in coffee can prevent and help brain function in Alzheimers Disease (Green Med Info)

Caffeine Lows:
Addictive:  Caffeine is addictive in even small amounts and it’s easy to become dependent on it.  If you miss your regular cup or try to come off it you may experience unpleasant withdrawal symptoms like tiredness, irritability, headaches, etc. 

It is a mild diuretic and makes your body lose more water, resulting in dehydration. If you are drinking many cups a day, do increase your water intake.

Osteoporosis: Caffeine has been shown to induce loss of calcium and influence the development of bones in animal studies. (Source: Green Med Info)

Caffeine can affect your sleep cycle, and for some people this may be even when they are having a small amount.  But when after a bad night’s sleep, they wake up tired, the irony is they turn to caffeine to keep them alert and awake the next morning!  

However, it’s important to realise that it affects everyone differently and if you are sensitive to it you may experience feeling shaky or jittery.  Also, as you build a tolerance to the amount you are having regularly, the intake begins to increase to get that “feel good” effect.  This can for some result in acid reflux, insomnia, poor sleep, etc.
In summary:
Having caffeine is highly controversial with so many mixed points of view.   Tea and coffee are two popular drinks with lots of varieties to chose from.  When having your drink the extras that are added to it like artificial sweeteners, sugar or cream can be more harmful than the caffeine. 
As with most things there are pros and cons, it’s important to find what works for your own unique body.  I would suggest you calculate how much caffeine you are consuming daily, using the USDA Food Content website.  If you are having excessive amounts of caffeine (over 400 mg/day) you should consider reducing it.  If you decide to reduce it never eliminate or reduce it drastically as you will suffer from strong withdrawal symptoms, like headaches.  Always, reduce it gradually so your withdrawal symptoms are mild.  And remember water should be your main hydrating drink.

[1] Caffeine and adenosine Ribeiro JA1Sebastião AM. J Alzheimers Dis. 2010;20 Suppl 1:S3-15. doi: 10.3233/JAD-2010-1379.

[2] Nall, A. H. et al. Caffeine promotes wakefulness via dopamine signaling in Drosophila. Sci. Rep. 6, 20938; doi: 10.1038/srep20938 (2016).