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Health Canada's recommendations on caffeine intake for women of child-bearing age and children were lowered in 2003 based on new research. For the rest of the general population of healthy adults, the long-standing advice still applies of no more than 400mg of caffeine per day, the equivalent of about three 8-oz (237ml) cups of brewed coffee.
Canadian adults get an estimated 60% of their caffeine from coffee and about 30% from tea. The remaining 10% comes from cola beverages, chocolate products and medicines.
For children aged one to five, about 55% comes from cola drinks, about 30% from tea, and about 14% from chocolate. The rest comes from other sources, including medicines.
For children age 12 and under, Health Canada recommends a maximum daily caffeine intake of no more than 2.5 milligrams per kilogram of body weight. Based on average body weights of children, this means a daily caffeine intake of no more than:
    • - 45 mg for children aged 4 - 6;
    • - 62.5 mg for children aged 7 - 9; and
    • - 85 mg for children aged 10 - 12.
Those recommended maximums are equivalent to about one to two 12-oz (355 ml) cans of cola a day.
For women of childbearing age, the new recommendation is a maximum daily caffeine intake of no more than 300 mg, or a little over two 8-oz (237 ml) cups of coffee.
For the rest of the general population of healthy adults, Health Canada advises a daily intake of no more than 400mg.

Caffeine sensitivity (the amount of caffeine that will produce an effect in someone) varies from person to person. On average, the smaller the person, the less caffeine needed to produce side effects. Caffeine sensitivity is most affected by the amount of caffeine a person has daily. People who regularly take in a lot of caffeine soon develop less sensitivity to it. This means they may need more caffeine to achieve the same effects.

Caffeine is a diuretic, meaning it causes a person to urinate (pee) more. It's not clear whether this causes...