Coffee or tea? These two drinks are certainly among our favorites, but how many of us exactly know what caffeine is? Caffeine, like nicotine, is legal, and while it's not addictive in the strictest sense, it can lead to a certain level of dependence over time. Unlike nicotine, caffeine is much more socially acceptable. However, whether you consume it occasionally or are addicted to it, knowing more about caffeine might surprise you.
Men have known about caffeine since prehistoric times. In nature, caffeine acts as a pesticide and is found in a number of plants: tea, coffee beans, guarana berries, and cocoa beans. Surprisingly, tea leaves contain the most caffeine, around 5%, compared to 1 to 2% in coffee beans.
The first known case of caffeine consumption in history dates back to 2737 BC when the Chinese Emperor Shen Nung accidentally drank water in which a few tea leaves had infused. China has remained a big tea enthusiast, with tea cultivation accounting for about 940,000 tons, or 27% of global production, in 2006. Coffee is native to Africa, and its earliest traces date back approximately 2,500 years when it was used as currency as well as a beverage.
Main sources of caffeine:
The scientific name for caffeine is 1,3,7-trimethylxanthine. We consume it in tea, coffee, soft drinks, energy drinks, and chocolate. Caffeine is an ingredient in some cold remedies, appetite suppressants, and analgesics and is effective against headaches and drowsiness.
Tea:
Green tea and black tea contain the same amount of caffeine as they come from the same plant (Camellia sinensis). However, red tea (Rooibos) comes from a different plant and does not contain caffeine. The caffeine content of a 150ml cup of tea varies between 30 to 100mg, depending on the infusion time and type. Loose tea contains more caffeine than tea bags.
Coffee:
There are two main varieties of coffee: Robusta and Arabica. Light-colored Robusta coffee beans contain more caffeine (2%) than Arabica beans (1%), especially since the roasting process removes some of the caffeine. A 150ml cup of filtered coffee contains between 100 and 150mg of caffeine, while the same amount of instant coffee provides 60 to 100mg, depending on the brand. Finally, a 150ml espresso contains approximately 90mg of caffeine.
Chocolate:
A whole 200g bar of chocolate provides around 550mg of combined methylxanthines (caffeine and other stimulants). A 30g chocolate bar contains between 20 and 60mg of caffeine, depending on the concentration of chocolate (dark or milk). This is noteworthy when assessing your daily caffeine intake or that of your children.
Energy drinks and sodas:
For those under 20, it's likely that soft drinks and energy drinks are the main source of caffeine. A 375ml cola drink contains approximately 40mg of caffeine, and an energy drink of 250ml contains 80 to 100mg of caffeine - roughly the same as an espresso.
The effects of caffeine on the body vary considerably among individuals. Standard recommendations set the limit at 600mg of caffeine per day for adults (equivalent to 4 cups of filtered coffee or 5 to 6 cups of tea). They are much lower for children, pregnant women, or those breastfeeding. The lethal dose of caffeine is 170mg/kg - for an average weight person, this equates to consuming about 10g of caffeine, or 80 to 100 cups at once – which is theoretically impossible to achieve.
The short-term effects of caffeine:
Caffeine is a central nervous system stimulant and a diuretic that acts on the body in various ways. On the cardiovascular system, caffeine causes an increase in heart rate and vasodilation. It also affects the respiratory and gastrointestinal systems. Caffeine affects respiratory functions: gas exchange is improved, muscle oxygenation is better, delaying muscle fatigue by providing more oxygen to the muscles and improving CO2 elimination.
If you have a cup of coffee before bed, you may find it difficult to fall asleep. Deep sleep and dream phases will be shorter, so you'll feel less rested upon waking. Indeed, after an hour to an hour and a half, caffeine reaches its peak concentration in the body. After three to seven hours, half of the caffeine consumed has been metabolized, moving from the blood to the urine, from which it is expelled from the body.
The stimulating effect of caffeine largely comes from its action on our membrane receptors to adenosine. Adenosine is a neuromodulator of the central nervous system that has specific receptors. When adenosine binds to its receptors, nerve activity slows down, and we become drowsy. Adenosine therefore facilitates sleep. However, caffeine is an antagonist of adenosine receptors. This means that it binds to the same receptors but without reducing neuronal activity. There are therefore fewer receptors available for adenosine, leading to neuron activation. The activation of several neuronal circuits by caffeine also causes the pituitary gland to release hormones that increase adrenaline production in the adrenal glands. As adrenaline is the fight-or-flight hormone, it increases our level of attention and gives a burst of energy to our entire body. This is an effect that coffee drinkers often seek.
The long-term effects of caffeine:
Excessive caffeine consumption (more than four or five cups of strong tea or coffee per day) causes tremors, an increase in heart rate, increased urination, nervousness, anxiety, stomach upset, and insomnia. Caffeine has a greater impact on children and the elderly. Babies whose mothers ingested too much caffeine during pregnancy may develop withdrawal symptoms at birth and suffer from hyperactivity and anxiety.
Stopping caffeine:
Caffeine is generally not considered addictive, but it can lead to dependence: the body develops a tolerance to this substance, meaning that more caffeine is needed to reproduce the same sensations. This is why caffeine consumption increases. Withdrawal symptoms occur because after a day or two without caffeine, the brain becomes hypersensitive to adenosine, causing a dramatic drop in blood pressure. The most common caffeine withdrawal symptom is headache. Other symptoms include drowsiness, irritability, and even nausea and vomiting.
The benefits of caffeine:
Caffeine is an antioxidant substance. Antioxidants can help prevent heart disease and some cancers. Coffee also contains flavonoids, which are also antioxidants. Caffeine increases alertness. It is used to improve concentration. People who work shifts or who are simply tired use caffeine as a stimulant. Caffeine has been used to help premature babies who have difficulty breathing. Apnea occurs when a newborn baby's central nervous system does not instruct the lungs to breathe. Administering tiny amounts of caffeine intravenously can stimulate a newborn's brain to initiate autonomous breathing. Taken in moderation, caffeine is harmless and can even be beneficial. Just keep an eye on your consumption to avoid suffering from insomnia.