Caffeine is a naturally occurring chemical called an alkaloid. It is found in the seeds, leaves and fruits of over 60 different types of plants, chiefly coffee and tea, but also in chocolate and some herbal beverages.

Caffeine stimulates the central nervous system in a manner that causes a short term elevation of blood pressure, an increased metabolic rate and increased blood flow to the muscles. This can produce enhanced mental alertness, an increased ability to concentrate, swift reaction times and prolonged vigilance for performing tasks.

Coffee also seems to be a mood elevator for most people and has even been linked to a reduced risk for depression amongst regular coffee drinkers. Coffee also impacts physical as well as mental endurance, which is why it can be used to enhance athletic performance.

How much caffeine is in your cup of coffee?

Serving Size
(unless otherwise
Milligrams of
(approximate values)
Brewed8 oz237 ml (1cup)135 mg
Roasted and ground, percolated8237118
Roasted and ground, filter drip8237179
Roasted and ground, decaffeinated82373
Instant823776 106
Instant decaffeinated82375

Health Canada guidelines for Caffeine intake is:
Average adult 400 mg/day (approx. 3 8oz cups)
Pregnant and breastfeeding women, and women trying to get pregnant 300 mg/day (just over 2 8oz cups)

A review undertaken by Health Canada scientists has re-confirmed that for the average adult, moderate daily caffeine intake at dose levels of 400 mg/day is not associated with any adverse effects. For anyone with a sensitivity to caffeine, decaffeinated coffee can be a great option.

Health Canada has not developed definitive advice for adolescents 13 and older because of insufficient data. Nonetheless, Health Canada suggests that daily caffeine intake for this age group be no more than 2.5 mg/kg body weight. This is because the maximum adult caffeine dose may not be appropriate for light weight adolescents or for younger adolescents who are still growing. The daily dose of 2.5 mg/kg body weight would not cause adverse health effects in the majority of adolescent caffeine consumers. This is a conservative suggestion since older and heavier weight adolescents may be able to consume adult doses of caffeine without suffering adverse effects.