Caffeine, a stimulant that occurs naturally in some foods and beverages and is added to others, is more widely consumed than you might think. It is present in coffee, tea, colas, energy drinks as well as chocolate, chocolate drinks and some flavours of ice cream. Some decaffeinated beverages also contain caffeine, though it’s usually a fraction of the normal amount.
In moderate doses, caffeine, which stimulates the central nervous system, can make you more alert and may have a beneficial effect on your memory, mood and general cognitive function. It has also been linked to a reduced risk of dementia, particularly Alzheimer’s disease.
However, in excess amounts, and in individuals who are sensitive to it, caffeine can cause side effects such as headaches, restlessness, rapid heartbeat, anxiety, irritability, insomnia, frequent urination and muscle tremors. Since it is highly acidic and can irritate the gastrointestinal tract, it is not recommended for individuals with gastric problems.
The safe limit for healthy adults is 400 mg of caffeine per day. Caffeine is not advised for children. Pregnant and breastfeeding women should check with their healthcare provider before having caffeine.
(Source: Center for Science in the Public Interest, Mayo Clinic)