Caffeine is a substance belonging to the alkaloid family , a group of compounds that are widespread in plants.

Caffeine, like the other alkaloids (atropine, nicotine , strychnine , morphine , etc.) is physiologically active on animals even at very low concentrations and is probably used by the plant as a defense mechanism against herbivores.

Even in humans, caffeine influences numerous biological reactions. Some of these interactions are beneficial for the body while others are responsible for the side effects of this substance.

Caffeine (mainly extracted from coffee, Coffea arabica, family Rubiaceae ), belongs to the group of purine alkaloids such as theophylline (from tea, Camellia sinensis, family Theaceae ), and theobromine (from cocoa, Theobroma, family Sterculiaceae ).

Caffeine is not only contained in coffee but is also found in other plants and foods. This is the case, for example, of coca cola , yerba mate , chocolate , Cola-based energizing drinks, herbal products such as guarana , not to mention analgesics, anti-cellulite cosmetics or medicines for diseases from cooling. It is curious to note, for example, how tea leaves have a caffeine content about double (2-4%) compared to coffee seeds (1-2%); however, due to the different extraction method, the infusion contains approximately four times less caffeine than the leachate.

Caffeine in Food

Drinks Caffeine content
COFFEE’ 85 mg (one cup).
COCA COLA 35-40mg (one can)
THE 28 mg/150 ml (the greater the longer the infusion is)
COCOA 100mg/100g
RED BULL 30mg/100ml
PLEASE NOTE: in sports it is necessary to take into account the cumulative effect of the caffeine taken with the various foods so as not to exceed the limits imposed by the anti-doping regulations. The caffeine content of traditional moka coffee is higher than that of espresso. In women, the use of some contraceptives ( ethinyl estradiol ) increases the duration of action of caffeine by about 50%.
INTESTINAL ABSORPTION TIME: about 45 minutes. HALF-LIFE : 2.5- 4.5 hours.


Effects of caffeine

Caffeine is the most widely used psychoactive drug in the world, its chemical conformation makes it in fact suitable for interacting with specific biological receptors that regulate the functionality of the cardiovascular , endocrine and nervous systems.

The intestinal tract absorbs caffeine very rapidly and peak plasma concentrations are observed about an hour after its ingestion. However, its metabolism is rapid and much higher than other stimulants such as amphetamines. Already after 3-6 hours from intake the plasma levels of caffeine are reduced by 50%.

Being lipophilic, caffeine has the ability to quickly pass the blood-brain barrier (a kind of virtual wall present in the brain , designed to prevent the passage of many molecules transported by the blood).

Caffeine also crosses the placenta and can be present in breast milk . During pregnancy and breastfeeding it is therefore advisable to greatly reduce the intake of coffee and other foods rich in caffeine.

Even if the effects of this substance are very numerous (as we will see in detail in a few lines) most of them are due to the stimulating effects that caffeine exerts on the entire body.


excitability, improvement of reflexes and ability to concentrate, analgesic action ,

ACTION MEDIATED BY INTERACTION WITH BIOLOGICAL RECEPTORS (cardiocirculatory and respiratory system):

thanks to its action as a competitive antagonist against adenosine receptors, caffeine promotes the release of two hormones called adrenaline and noradrenaline.

Catecholamines favor the increase of body metabolism , heart rate , blood pressure and number of breaths (thus increasing blood oxygenation )


increased gastric acid synthesis, increased diuresis ;

if applied to the skin using specific cosmetics (creams, gels and patches), it is useful in the treatment of localized fat deposits.


Caffeine, sport and doping

If taken within the maximum permitted levels, caffeine has a positive effect on the performance of most athletes. Even fairly moderate doses (200-400 mg) ingested one hour before competition improve alertness, concentration and endurance . Given the great individual variability, however, it is advisable to experiment with its use in training before taking it in competition.

An athlete tests positive for doping controls when the concentration of caffeine in his urine exceeds 0.012 mg/ml (= 12 mcg/ml). It is not easy to establish exactly what dose of intake is able to overcome this threshold . In general, it is recommended not to drink more than 6-8 cups of espresso or two or three cups of traditional coffee in the three hours preceding the competition.


Caffeine and weight loss

By virtue of their high caffeine content, tea and coffee are often recommended to promote weight loss (in association with a correct diet). Several studies have confirmed this property, which finds a logical explanation in its stimulating effect on the basal metabolic rate . In particular, 500 mg of caffeine (the equivalent of 5 or 6 coffees) increase the basal metabolic rate by 10-15%. Translated into simpler and more immediate terms, a similar level of intake allows you to consume 100-500 calories more per day (in relation to body size and above all to the muscle mass of the subject).

Caffeine is a characteristic ingredient of cosmetics to treat cellulite and localized fat deposits; applied to the skin, it promotes the mobilization of triglycerides from the subcutaneous adipose tissue mediated by lipolytic lipase.

OTHER USEFUL INFORMATION: chewing 1-2 coffee beans helps purify the breath after a large meal. Coffee does not favor digestion , on the contrary, if taken with a lot of sugar or even worse with cream or alcohol , it slows it down. However, the stimulating effects of caffeine can give the feeling of apparently better digestion.


Negative effects of caffeine

Coffee reduces the absorption and bioavailability of some substances:

riboflavin or vitamin B2

calcium (reduce consumption in the presence of osteoporosis and bone fractures )



A caffeine poisoning caused by the massive intake of this substance (over 500-1000 mg in relation to individual sensitivity) causes unrestrained excitement, nervousness, insomnia and tachycardia

Caffeine should therefore be taken in moderation in case of:

esophagitis and gastroesophageal reflux (in addition to increasing the harmful power of gastric juices, caffeine relaxes the esophageal sphincter , a kind of valve that prevents the gastric contents from rising into the esophagus )

stomach ulcer



tachycardia, arrhythmias and heart problems in general


Prolonged use of caffeine tends to dampen the previously seen beneficial effects and, if taken in high doses, accentuates the collateral ones (acidosis, pulmonary edema , hallucinations ).

Several studies have described the presence of a mild withdrawal syndrome .



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