Myths about coffee, tea and cocoa
Typically, the morning begins with a cup of hot, invigorating drink: coffee, tea or cocoa. And nothing new, because all of these drinks contain the same substances from the group of methyl xanthines - alkaloids with a psychostimulating effect.
According to the most common legend, the tonic properties of coffee were discovered by an Ethiopian shepherd who noticed that goats, having eaten dense leaves and dark red fruits of a coffee tree during the day, stopped sleeping at night. He told about this strange case to the abbot of the monastery, he decided to try on himself the action of unusual grains and was struck by the force of the drink!
In order to maintain the vigor of the monks who fell asleep during night prayers, he ordered them to drink a decoction that relieves fatigue. It happened in the 9th century, but coffee was recognized worldwide much later. Peter I brought coffee beans to Russia along with potatoes, tobacco, and other European novelties. He, according to historians, forcibly treated those close to him with a “bitter swill”.
The history of caffeine is more transparent: it was discovered and given its usual name by the German chemist Ferdinand Runge in 1819, and in 1828 the French Pelletier and Cavant managed to get the substance in its pure form.
Four years later, the Germans Veler, Pfaff and Liebig found out the chemical formula. German Emil Fischer was able to reproduce caffeine in the laboratory, who, incidentally, owes this work to his 1902 Nobel Prize in Chemistry.
Tangle of contradictions
However, this is where the clarity ends, and the real dark forest begins. The fact is that so far there is no final and well-established idea of either the mechanism of action of caffeine, or its effect on the body! The data on the doses and effects that medical college students studied twenty years ago as the generally accepted properties of caffeine are now completely obsolete.
The number of studies of coffee in general and caffeine in particular is growing: if in 1970 less than a hundred articles on this topic were published, then in 2013 - 800, and in 2014 more than a thousand are expected. This is due not only to the fact that some special hopes are assigned to caffeine, but also to the fact that coffee is an extremely popular food product. Not surprisingly, its manufacturers and sellers are extremely interested in a positive image.
Coffee companies sponsored a huge amount of research, published mainly in not-most-quoted magazines, sometimes there is not even a practice of reviewing materials by several independent experts. Basically, small groups (30–100 people) are involved in such works, information is collected using questionnaires, and there are many questions regarding the design of studies. But they win the mass.
Suffice it to say that the results of the first truly independent and large-scale study of the impact of coffee on human health were published only in May 2012. On any information about the negative impact of coffee on health, a dozen rebuttals will be found. Readers will not delve into the nuances, understand the sources of financing and methodological errors of researchers, so it is very, very difficult to find truly reliable information in this stream. But you can.
Drink coffee on health
Let's start with the most important thing - the mechanism of action. Caffeine by its very nature resembles the neurotransmitter adenosine - in both cases, the basis of the compound is the purine base adenine, one of the components of DNA. This means that caffeine can bind to the same receptors as adenosine, successfully competing with it. To date, four subtypes of adenosine receptors are known: A1, A2A, A2B, and A3, but most effects are realized through A1. Adenosine has an inhibitory effect on the central nervous system, it works as a kind of protector for injuries or stresses, preventing the brain from overheating.
Caffeine weakens the effect of sleeping pills and narcotic painkillers.
Caffeine also binds to this subtype of receptors, and it was possible to establish a specific mechanism only relatively recently - at the end of 2012. German researchers from the Institute of Neurophysiology and Medicine used one of the latest advances in imaging diagnostics - positron emission tomography (PET). The study involved 15 male volunteers. For 36 hours, they refrained from drinking coffee, after which they underwent PET with the fluorine-18 isotope (F-18-CPFPX), which does not bind tightly to the A1 receptors. The participants were then given caffeine in the form of short intravenous injections, gradually increasing the volume administered. Caffeine bound to A1 receptors, displacing F-18-CPFPX. After this, the PET was repeated. The results showed that at a caffeine concentration of 13 mg / l (equivalent to 4–5 standard portions of espresso), 50% of A1-adenosine receptors are occupied. Thus, caffeine does not have a direct excitatory effect on the central nervous system, but only temporarily prevents the binding of adenosine to its receptors and the development of the inhibitory effect of this neurotransmitter.
The status of caffeine as a drug is doubtful, although scientists agree that addiction to coffee still occurs. But, as emphasized in all manuals, the addictive potential of caffeine is extremely low. That is, a person may well live without coffee, and no serious “breakdown” occurs against the background of refusing an invigorating drink. With intensive consumption of coffee (more than 300 mg of caffeine per day), the number of A1-adenosine receptors increases. If coffee disappears from the diet, the inhibitory effect of adenosine, which now has no one to compete with, can clearly manifest itself. But the situation quickly bounced back. Nevertheless, an overdose of caffeine is possible, with consequences up to death (theoretically). Toxicologists have calculated that a lethal amount may be a cup of espresso per 1 kg of body weight, and this dose should be drunk in a relatively short time interval (about half an hour).
Consuming coffee within reasonable limits does not harm the heart. At least at the moment there is not a single statement about the negative effect of caffeine on the "flame motor", which would not have been repeatedly refuted. Moreover, a meta-analysis of studies conducted in 2014 by Chinese scientists and including data on 228,465 participants showed that people who drink coffee have atrial fibrillation 6% less likely than those who don’t drink it.
Persistent hypertension does not occur in coffee lovers, with very rare exceptions - with prolonged use of more than 1 liter of drink per day, systolic pressure may increase by as much as 10 mm Hg. Art.
The carcinogenicity of the drink is a big question, although it is included by the International Agency for Research on Cancer (IARC) in the 3rd group of carcinogens (theoretically dangerous for humans, but the absence or lack of reliable studies does not allow us to make a final conclusion about their carcinogenicity). In the same group, by the way, are mobile phones, talcum powder and almost 500 more items. Meanwhile, it turned out that lovers of an invigorating drink are less likely to suffer from aggressive prostate and breast cancer. And many research groups today are eyeing caffeine as a versatile vehicle that facilitates the flow of anticancer drugs, for example, into the brain.
But some fears were nevertheless confirmed. For example, pregnant women are not recommended to exceed the daily dose of 200 mg of caffeine, since it negatively affects the fetus - in particular, it increases the risk of having a baby with a cleft lip and heart defects
Theobromine is the main biologically active ingredient in cocoa and chocolate and the closest relative to caffeine. In cocoa, this alkaloid can be from 2 to 10%, ten times more than caffeine. Slightly less (1? 2%) - in cola nuts, guarana berries, tea leaf. In coffee, by the way, theobromine is not at all. Theobromine was first isolated by the outstanding Russian chemist A. A. Voskresensky in 1841 from cocoa beans, and the synthetic analogue was received in 1882 by the already mentioned Nobel laureate German Emil Fischer.
Unlike coffee, where all the positive and negative effects are tied to caffeine, the positive effects of cocoa or chocolate on the body are associated with anything but not theobromine. The fact is that theobromine is a weaker adenosine antagonist than caffeine, it has almost no effect on the central nervous system. And his addictive potential tends to zero. The main action of theobromine is the relaxation of smooth muscles. It is achieved in two ways - inhibition of the enzyme phosphodiesterase (PDE) and a decrease in calcium intake through cell membranes. This effect is widely used in medicine, theobromine is a medicine used to expand the bronchi, reduce peripheral vascular resistance and reduce pressure in the pulmonary circulation. It also increases the blood flow in the coronary arteries, the contractility of the myocardium and increases the heart rate. True, this leads to an increase in the oxygen demand of the heart, so the “cores” need to be careful with products containing a large amount of cocoa.
Theobromine is more toxic than caffeine. Chocolate poisoning of people with a mutation in the gene responsible for the synthesis of the hepatic enzyme cytochrome P450 CYP3A4 is described. Horses, dogs and cats are extremely sensitive to this substance - chocolate is categorically contraindicated to them. The lethal dose of LD50 for dogs is 300 mg / kg, for cats - 200 mg / kg.
Tea (any) contains all three methylxanthines at once. But the main active ingredient here is theophylline. It was discovered in 1888 by the German biologist Albrecht Kossel, and the first synthetic method was proposed by his compatriot German Emil Fischer (yes, the same one). True, another method of synthesis, proposed in 1900 by Wilhelm Traube, has taken root in industry.
Theophylline is very similar to theobromine, and its effects are similar. The only difference is that theophylline has a diuretic effect. The rest is similar: smooth muscle relaxation, expansion of peripheral vessels and increased myocardial contractility.
As with cocoa, the main beneficial effects of tea are associated with polyphenols and other antioxidants, but not with theophylline. Which, by the way, is also a medicine. And this must be taken into account when trying to drink any medicine with tea. So, the effect of the diuretic furosemide will increase, and the “cardiac” beta-blockers will work much worse. In the instructions for theophylline, the section "Drug Interaction" occupies a whole page.
But with respect to all three of these methylxanthines, it is better to be guided by the golden rule: "The main thing is without fanaticism . "
Coffee or tea?
The Swedish king Gustav III was an ardent opponent of coffee and tea, since he considered them unhealthy. To prove this, he conducted an original scientific study, replacing twin criminals with a life sentence with the condition that the first would drink three cups of coffee, and the second three cups of tea a day.
A doctor was assigned to each prisoner.
First, the first doctor died, then the second, then Gustav himself was killed in 1792, and both prisoners lived to a very old age.
At least, it is known that the twin, “sentenced” to tea, died at the age of 83, and the story is completely silent about the second participant in the experiment.
The most dangerous combination is coffee and alcohol. Caffeine penetrates well through the blood-brain barrier and pulls ethanol along with it, accelerating intoxication.
But at the same time, the “anti-inhibitory” effect of caffeine for some time balances the depressive effect of alcohol, as a result of which “sober intoxication” develops: a person believes that he can still drink, although he has long exceeded his dose.
In addition, the products of alcohol metabolism significantly increase the "arrhythmic readiness" of the heart, and in this case even a small dose of caffeine can cause a malfunction.
In the USA, fatal cases were recorded after drinking alcohol-containing “energy drinks” in young people aged 20–25 years old, the cause of death was atrial fibrillation or heart attack. After that, a number of states banned such drinks.