- What is caffeine?
- Which foods contain caffeine?
- How much caffeine do individuals consume?
- How much caffeine is it safe to consume?
- Metabolic and other affects of caffeine
- Caffeine addiction
- Caffeine withdrawal
Caffeine is a natural substance found in more than 60 plant species. These include tea leaves, coffee beans, guarana and cocoa seeds. Caffeine can also be produced synthetically and added to certain foods, beverages and medications.
Caffeine is one of a group of drugs called methylxanthines, which have several effects on the body:
- They stimulate the central nervous system;
- They increase the frequency of urination (are diuretics);
- They stimulate the heart muscle; and
- They increase smooth muscle relaxation, which affects body systems regulated by smooth muscles, including the endothelial system which regulates blood flow.
Caffeine is the most commonly consumed psychoactive (affecting the mind or moods) drug globally and the consumption of natural caffeine has a long history. Coffee has been consumed in Arabia since the 13th century and tea has been consumed in China for several thousand years.
Caffeine is found in many foods, beverages and medications. Naturally occurring caffeine is found in coffee, tea, cocoa and chocolate.Some nuts also contain caffeine, for example kola nuts which are consumed as a nut but also used to make tea in parts of West Africa. Caffeine is also present in many soft drinks, particularly cola flavoured drinks and energy drinks. A typical cola drink will contain about one third to one quarter the amount of caffeine found in an equal volume of coffee.
However, it is important to note that not all the caffeine contained in a product is necessarily detailed in the ingredient list. If caffeine occurs naturally in an ingredient of the product (e.g. guarana) the ingredient may be listed but not the caffeine it contains. Only if synthetically produced caffeine is added will it appear on the ingredients list as caffeine. In addition, caffeine can be removed from foods in which it is naturally found through a process known as decaffeination, for example with decaffeinated coffee and tea.
Globally, the average caffeine intake per person is 70mg per day (approximately equivalent to the amount of caffeine contained in one cup of instant coffee). However, individuals in developed countries consume more caffeine. In the United States, individuals consume on average 200mg (1-1.5 cups of coffee brewed from coffee beans) of caffeine per day.
In Australia, research conducted in the 1980s indicated that average per capita caffeine consumption is 240mg per day (about two cups of coffee bean coffee per day). This equates to 2.8 kg of coffee and 5.8 kg of chocolate per person per year.
The amount of caffeine which can be safely consumed varies between individuals. In Australia, health authorities recommend that adults consume no more than 600mg of caffeine per day. However, individuals who are sensitive to the effects of caffeine consumption, particularly pregnant and lactating women and children, should consume less caffeine.
When a human consumes caffeine, the substance is absorbed, distributed and excreted in the urine very quickly. It does not accumulate in the bloodstream or body tissues. Following absorption, caffeine is directed to the brain where it stimulates the nervous system. It also stimulates the heart and increases smooth muscle relaxation. As smooth muscles regulate the flow of blood through the body, this can affect an individual’s blood flow.
Caffeine is metabolised by the liver and is typically excreted in urine within several hours of consumption. While it remains in the body caffeine increases the release of free fatty acids stored in fatty tissues. It also affects the kidneys, which causes increased urination which may in turn cause an individual to become dehydrated.
Caffeine is an addictive substance. Following regular consumption of as little as 350mg of caffeine per day (within the recommended safe limits, equivalent to roughly three cups of coffee bean coffee) an individual may become dependent on caffeine. Caffeine addiction can be physical or psychological and varies in severity. Some addicted individuals will be mildly dependent on caffeine while others will compulsively consume caffeine.
Individuals who are addicted to caffeine may experience withdrawal symptoms if they stop consuming caffeine. Individuals who consume large amounts of caffeine and wish to reduce their consumption, should therefore reduce caffeine consumption gradually, for example by substituting one caffeinated drink per day with a non-caffeinated beverage.
Caffeine withdrawal may result in side effects in caffeine dependent individuals. Symptoms usually begin 12-24 hours following the last dose of caffeine and persist for 24-48 hours. However, heavy caffeine consumers may experience withdrawal symptoms earlier (within six hours of the last dose) and the symptoms may last for a longer period of time.
Symptoms of caffeine withdrawal include:
- Headaches, which are the key symptom of caffeine withdrawal;
- Nausea; and/or
|For more information on caffeine, including consumption by adults, children and pregnant women, as well as some useful tools, see Caffeine.|
|For more information on nutrition, including information on types and composition of food, nutrition and people, conditions related to nutrition, and diets and recipes, as well as some useful videos and tools, see Nutrition.|
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