By Dr Catherine Thiron.

Coffee contains a variety of substances including caffeine. A lot has been written about caffeine. What is the position today?

Caffeine is an alkaloid, or more exactly, a methylxanthine, which is found in many plants, including coffee beans, but also in tea leaves, cocoa beans, guarana seeds and kola nuts. It is found in the composition of various drugs and beverages.

Coffee beans contains 1 to 2% of caffeine, i.e. 10 to 20 g for 1 kg of coffee beans.

Metabolism and effects of caffeine

Caffeine reaches the blood circulation 30 to 45 minutes after it has been ingested. It is then distributed through body water, metabolised and then eliminated through urine. It has an average half-life of approximately 4 hours in the body (estimates vary between 2 and 10 hours). Its metabolism slows down during pregnancy and this explains why the caffeine content stays longer in pregnant women.

Caffeine is a stimulant of the nervous system, wakefulness and memorisation processes. It reduces the sensation of fatigue.

It increases physical performance and stamina during extended activities of sub-maximal intensity.

Its effects are also felt on the heart: tachycardia, slight peripheral vasodilatation and mild diuretic activity.

The lethal dose of caffeine in humans is 10g/day (or the equivalent of 130 espresso cups of Arabica).

With occasional coffee drinkers, drinking one cup is enough to create a boost of adrenalin, noradrenalin and rennin (stress hormones with cardiovascular stimulatory effects) and a consumption of more than 6 to 7 cups per day has an anxiogenic effect.

Chronic high consumption of caffeine in association with other food parameters (low consumption of calcium and vitamin D, high salt and alcohol intake) is cited as an aggravating factor of osteoporosis.

With pregnant women, there doesn't seem to be an effect on birth weight, however the booster properties of the caffeine ingested by the mother can be perceived in the foetus (longer periods of wakefulness). Caffeine does not seem to be teratogenic in humans in the doses taken in. However, it may potentiate the action of other toxic agents (alcohol, tobacco, drugs, etc.).

In other words, pregnant women are advised to consume coffee and tea in moderate amounts.

Overall, studies conducted by various teams do not demonstrate any link between coffee consumption (under 5 cups per day) and cardiovascular diseases or sudden death or arrhythmia.

There is nothing to prove that caffeine consumption is a risk factor of cancer in human beings. On the contrary, experimental studies have concluded that caffeine protects the lungs from the carcinogenic action of nitrosamines.

Likewise, consuming at least 2 cups of coffee each day is supposed to protect against colorectal cancer in humans.

Caffeic acid, a polyphenol found in coffee.

Polyphenols are micro-nutrients found in plants. Their type and content varies a lot from one species to another.

For several years now, there has been growing interest in polyphenols among nutritionists, food processing companies and consumers, mainly because of their antioxidant properties. For example, they may contribute to the prevention of a range of pathologies related to oxidant stress such as cancers, cardiovascular diseases, osteoporosis and inflammatory diseases.

One polyphenol is caffeic acid, found in coffee and in smaller quantities in many fruits and vegetables.

Several in vitro studies are currently being carried out, as well as in vivo tests on animals and volunteer human subjects to find out about how they are absorbed into the intestine, their metabolism, and of course, the effects of the different polyphenols.

The results have not yet been published.

EthiopianSidamo /span>.

This is a coffee from the high plateaux of Ethiopia.

Ethiopia is the country from where the Arabica variety originated. It used to grow wild in the forest and was gathered by picking.

Today, it is a carefully cultivated shrub that produces a mild beverage with a floral scent.

It has a very low caffeine content of less than 1%, which is one of the lowest in Arabica coffees which are already milder than Robusta coffees).

Conclusion.

Aside from pregnant women and people with heart conditions, a reasonable consumption of coffee (roughly 4 cups per day), and in particular, coffees, like the Ethiopian Sidamo with a low caffeine content, is not harmful to health.