Caffeine is part of modern life. But are caffeine-rich drinks and foods harmful or not?
Until quite recently, most research studies on caffeine warned that caffeine intake was harmful and for years high levels of caffeine in the diets of sportsmen and women were banned by the World Anti-Doping Agency (WADA).
However, recently a number of studies have shown that caffeine in moderate doses may be beneficial to health. As a result, the WADA lifted its ban on caffeine as a performance-enhancing drug in sport in 2004.
What do we know at the moment about caffeine and its effects on health, sport and slimming?
What is caffeine?
Caffeine is a member of the family of chemicals that are called methyl xanthines. It is variously classified as a stimulant, an addictive substance, a performance-enhancing drug and a slimming aid.
Sources of caffeine
Caffeine is found in many drinks, foods and medications. Examples include coffee, tea, cola drinks, the new generation 'energy' drinks such as Red Bull, chocolate, and many over-the-counter and prescription medications.
Most headache pills, pain pills, many cough remedies and most slimming pills also contain caffeine.
Caffeine content of foods and drinks
A recent edition of FoodInfo, the Newsletter of the International Food Information Service published in June of this year, featured the following table of the typical caffeine content of foods and beverages:
Food or beverage
Typical caffeine content
1 mug of instant coffee
100mg
1 cup of brewed coffee
100mg
1 cup of instant coffee
75mg
1 cup of tea
50mg
1 can of cola
less than 40mg
1 can of caffeine-containing "energy"
drink
80mg
1 chocolate bar (50g)
less than 50mg
1 typical headache tablet*
50mg
(Adapted from: "Focus on caffeine. FoodInfo, June 2006, p. 7)
* Painkillers selected at random
Side effects of caffeine
Caffeine is a stimulant that can cause the following side effects:
rapid, irregular heartbeats and palpitations
restlessness, nervousness and irritability
tremors (the shakes)
headache
abdominal pain, nausea, vomiting, and diarrhoea
diuresis (increased urination)
Another negative effect of caffeine is its potential for addiction. We all know people who cannot function without their "caffeine fix" and many individuals are clearly addicted to tea, coffee, cola drinks and chocolate.
Caffeine also increases blood pressure, even in healthy individuals, but particularly in the elderly. Persons who already suffer from high blood pressure may find that ingesting large quantities of caffeine pushes their blood pressure up to unacceptable levels.
Excessive intakes of caffeine contribute to osteoporosis and may interact negatively with prescription medications.
Research indicates that women who ingest excessive quantities of caffeine, do not conceive as fast as women who drink moderate quantities of this stimulant.
The birth weight of babies born to pregnant women who drink or eat too much caffeine may be low, which exposes the newborn to a number of risks.
In addition, caffeine passes into breast milk and can transfer all the negative effects listed above to the infant. So, if your baby is irritable, restless or exhibits any of the other side effects of caffeine excess, this may be due to you, the mother, ingesting too much caffeine.
Positive effects of caffeine
Recent research indicates that caffeine intake can reduce the risk of developing Parkinson's disease and possibly also liver cancer. There are indications that caffeine may decrease liver damage.
Another positive effect is that caffeine can increase the resting metabolic rate (RMR) in lean and obese people, which is why it is often included in slimming pills and products, including herbal diet pills (see next week's DietDoc topic).
Caffeine is known to enhance athletic performance, reduce fatigue and improve recovery in athletes (see next week's DietDoc topic).
Because of its stimulant properties, caffeine can also help people stay awake and be more alert in situations where they are required to concentrate.
How much caffeine should we have?
Experts agree that moderate intakes of caffeine should not be harmful to the general population.
The UK Food Standards Agency has, for example, recommended that the general population and pregnant women should not have more than 300mg of caffeine a day (e.g. four cups of instant coffee or six cups of regular tea). This is probably a reasonable recommendation which we can also apply in South Africa.
Just keep in mind when you calculate your daily caffeine intake to include caffeine arising from any medications you may be taking, as having three headache pills would contribute 150 mg of caffeine to your intake.
Present knowledge indicates that moderate intakes of caffeine should not be harmful to most people, and that caffeine may even have positive effects in preventing some diseases. As is so often the case, moderation in caffeine consumption seems to be the sensible path to follow. – (Dr Ingrid van Heerden, DietDoc)
Reference:
(F Rogers (2006). Focus on Caffeine - Is it worth losing sleep over? FoodInfo , June 2006, pp.6-7).
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