Caffeine is a stimulant and an irritant from the methylxanthine family. It affects the body's metabolism by stimulating the release of certain brain chemicals. Not only does caffeine increase vigilance, gastric acid secretion, and urine output, but it can also increase the heartbeat, blood pressure, and breathing rate. People who drink caffeine-containing drinks only occasionally are especially susceptible to these effects. They may also have headaches and feel irritated and nervous. On the other hand, those who drink a lot of caffeine-containing drinks experience these same effects when they abruptly stop drinking caffeine (withdrawal symptoms).
Caffeine, therefore, can be beneficial to those who need to stay awake or want to boost their intellectual capacities temporarily and detrimental to those who suffer from insomnia, heart problems, reflux, or have an ulcer.
Note that decaffeinated coffee stimulates gastric secretion as much as regular coffee. Thus other substances, besides caffeine, appear to play a role in this effect...
So as long as there are no health problems that could be worsened by caffeine intake, moderate consumption (250 mg/day) is not detrimental to one's health.
Where else is caffeine found besides coffee?
Caffeine is found in tea and chocolate, certain pain-killers (e.g., Anacin™, Fiorinal™), some soft drinks, and in products used to keep us awake (e.g., Wake-Up™).
Caffeine is also found in various natural products, e.g. cocoa nuts, bissy nuts, cacao (cocoa), guarana, mate (Paraguay tea, St. Bartholomew's tea, Jesuit's tea), and green tea. Most of the time, the quantity of caffeine is unknown.
In order to assess your daily intake of caffeine, here is a list of products and their approximate caffeine content:
A. Caffeine and heart disease
It has now been proven without a doubt that caffeine is partly to blame for arrhythmia (irregular heart beat). For many years, researchers were confounded by the fact that, in general, heavy coffee drinkers also have bad health habits: often they are sedentary (do not exercise), smoke, and eat fatty foods. And all these bad habits increase the risk of heart disease...!
B. Caffeine and fibrocystic disease of the breasts
No relationship has been established between caffeine consumption and fibrocystic disease of the breasts. Moderate caffeine consumption is not known to increase the incidence of this disease and stopping caffeine does not reduce breast pain or tenderness.
C. Caffeine and pregnancy or cancer
No study has shown any relationship between caffeine and cancer or congenital birth defects.
Even so, pregnant and breast-feeding women and people with heart disease should limit their caffeine intake to no more than 200 mg per day.
Caffeine's pharmacological effects
For a long time caffeine-based drugs have been used to increase vigilance and stay awake (e.g., Wake-Up™). Furthermore, adding 65 mg of caffeine to certain analgesics, such as acetaminophen (Tylenol™), Aspirin and ibuprofen (e.g., Advil™), increases their analgesic effect.
Finally, certain drugs and medical conditions can modify caffeine elimination. For example, while nicotine increases caffeine elimination, pregnancy and certain drugs (ex. cimetidine [Tagamet™], quinolone antibiotic) decrease it.
Moreover, caffeine can affect the results of certain diagnostic tests