Myths about coffee, tea and cocoa
As a rule, the morning begins with a cup of hot, invigorating drink: coffee, tea or cocoa. And nothing new, because all these drinks contain the same substances from the group of methyl-xanthines - alkaloids that have a psycho-stimulating effect.
According to the most common legend, the tonic properties of coffee were discovered by the Ethiopian shepherd who noticed that the goats, after eating the dense leaves and dark-red fruit of the coffee tree, ceased to sleep at night. He told about this strange case to the abbot of the monastery, he decided to try the unusual grains on himself and was amazed by the impact of the drink!
In order to support the vivacity of the monks who fell asleep during the night prayers, he ordered them to drink a decoction, which relieves fatigue. This happened in the IX century, but the world's recognition of coffee was received much later. In Russia coffee beans along with potatoes, tobacco and other European novelties were brought by Peter I. He, according to historians, forcibly treated him to the "bitter smell" of his associates.
The history of caffeine is more transparent: it was discovered and given the name of the German chemist named 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. And Herman Emil Fisher, who, incidentally, was also responsible for his work in the Nobel Prize in Chemistry, was able to reproduce the caffeine in the laboratory.
Tangle of contradictions
However, on this clarity ends, and a real dark forest begins. The fact is that so far there are no definitive and established ideas about the mechanism of caffeine action, nor its effect on the body! The data on the doses and effects that medical college students taught 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 there were fewer than 100 articles on this topic, then in 2013 - 800, and in 2014, they are expected to more than a thousand. This is due not only to the fact that caffeine has some special hopes, but also because coffee is an extremely popular food product. Not surprisingly, its producers and sellers are extremely interested in a positive image.
Coffee companies sponsored a huge number of studies published mainly in the most not cited journals, sometimes there is not even practice of peer review of materials by several independent experts. In general, small groups (30-100 people) are involved in such works, information is collected using questionnaires, and there are many questions to the design of research. But they win by mass.
Suffice it to say that the results of the first truly independent and large-scale study of the influence of coffee on human health were published only in May 2012. For any information about the negative effect of coffee on health, there will be a dozen denials. Readers will not delve into the nuances, understand the sources of funding and methodological mistakes of researchers, so finding truly reliable information in this flow is very, very difficult. But you can.
Drink coffee for health
Let's start with the most important - the mechanism of action. Caffeine by its nature is very similar to the neurotransmitter adenosine - in both cases, the compound is based on the purine base adenine, one of the constituents 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 a deterrent effect on the central nervous system, it works as a kind of defender in injuries or stresses, preventing "overheating" of the brain.
Caffeine weakens the effect of sleeping pills and narcotic analgesics.
Caffeine is also associated with this receptor subtype, and a specific mechanism was established only relatively recently - at the end of 2012. German researchers from the Institute of Neurophysiology and Medicine used one of the latest achievements in visualization diagnostics - positron emission tomography (PET). The study involved 15 male volunteers. For 36 hours, they refrained from consuming coffee, after which they conducted a PET with a fluorine-18 isotope (F-18-CPFPX), which binds weakly to the A1 receptors. Then the participants were given caffeine in the form of short intravenous injections, gradually increasing the volume administered. Caffeine contacted A1 receptors, displacing F-18-CPFPX. After this, repeated PET. The results showed that at a concentration of caffeine 13 mg / l (equivalent to 4? 5 standard portions of espresso), 50% of the A1-adenosine receptors are employed. Thus, caffeine does not have a direct stimulating 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 questionable, although scientists agree that addiction to coffee still occurs. But, as emphasized in all the guides, the addictive potential of caffeine is extremely low. That is, a person can quite live without coffee, and no serious "breaking" against the backdrop of refusing an invigorating drink does not arise. With intensive consumption of coffee (more than 300 mg of caffeine per day), the number of A1-adenosine receptors increases. If the coffee disappears from the diet for a while, the braking effect of adenosine, which now has no one to compete with, can clearly manifest itself. But the situation quickly returns to normal. Nevertheless, an overdose of caffeine is possible, with consequences up to a lethal outcome (theoretically). Toxicologists have calculated that a lethal amount can be an espresso cup per 1 kg of body weight, which should be drunk in a relatively short time interval (about half an hour).
Consumption of 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 "fiery motor," which would not have been repeatedly refuted. Moreover, a meta-analysis of research conducted in 2014 by Chinese scientists and including data on 228,465 participants showed that people who drink coffee ciliary arrhythmia develops 6% less frequently than those who do not drink it.
Persistent hypertension does not occur in coffeemakers, with very few exceptions - with prolonged use of more than 1 liter of drink per day, it is possible to increase systolic pressure by "whole" 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 group 3 of carcinogens (theoretically dangerous for humans, but the absence or lack of reliable studies does not allow conclusive conclusion about their carcinogenicity). In the same group, by the way, there are mobile phones, talcum and almost 500 more names. 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 look at caffeine as a universal vehicle that facilitates the receipt of antitumor drugs, for example, in the brain.
But some fears were 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, increases the risk of having a baby with a "hare lip" and heart defects
Theobromine is the main biologically active ingredient in cocoa and chocolate and the closest relative of caffeine. In the cocoa of this alkaloid can be from 2 to 10%, tens of times more than caffeine. Slightly less (1? 2%) - in cola nuts, guarana berries, tea leaf. In coffee, by the way, the 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 obtained in 1882 by the already mentioned Nobel laureate Hermann Emil Fisher.
Unlike coffee, where all the positive and negative effects are tied to caffeine, the positive effect of cocoa or chocolate on the body is associated with anything, but not with theobromine. The fact is that theobromine is a weaker adenosine antagonist than caffeine, it has almost no effect on the central nervous system. And the addictive potential of it tends to zero. The main effect of theobromine is the relaxation of smooth muscles. It is achieved by 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 medicament used to dilate the bronchi, reduce peripheral vascular resistance, and reduce pressure in the small circulation. It also increases blood flow in the coronary arteries, myocardial contractility and heart rate increases. True, this leads to an increase in the need of the heart in oxygen, so that the "cores" need to be careful with products containing large amounts of cocoa.
Theobromine is more toxic than caffeine. Chocolate poisoning of people with a mutation in a gene responsible for the synthesis of the hepatic enzyme cytochrome P450 CYP3A4 is described. Extremely sensitive to this substance are horses, dogs and cats - they are categorically contraindicated in chocolate. 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 substance here is theophylline. It was opened in 1888 by the German biologist Albrecht Kossel, and the first method of synthetic reception was proposed by his compatriot Hermann Emil Fisher (yes, the same one). True, the industry adopted another method of synthesis, proposed in 1900 by Wilhelm Traube.
Theophylline is very similar to theobromine, and it causes similar effects. The only difference is that theophylline has a diuretic effect. The rest is similar: a relaxation of a smooth musculature, expansion of peripheric vessels and strengthening of contractile capacity of a myocardium.
As in the case of cocoa, the main positive effects of tea are associated with polyphenols and other antioxidants, but not with theophylline. Which, by the way, is also a medicinal product. And this must be taken into account when trying to drink any medicine with tea. So, the effect of diuretic furosemide will increase, and "cardiac" beta-blockers will work much worse. In the instructions to theophylline, the section "Drug Interactions" takes a whole page.
But with respect to all the three listed methylxanthines, it is better to follow the golden rule: "The main thing is without fanaticism . "
Coffee or tea?
Swedish King Gustav III was an ardent opponent of coffee and tea, because he considered them harmful to health. To prove this, he conducted an original scientific study, replacing the twin criminals with execution for life imprisonment on the condition that the first one 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 doctor, then in 1792 Gustav himself was killed, 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 years, and the second participant in the experiment, the story is completely silent.
The most dangerous combination is coffee and alcohol. Caffeine penetrates well through the blood-brain barrier and "pulls" behind itself ethanol, accelerating intoxication.
But at the same time, the "anti-braking" effect of caffeine balances the depressive effect of alcohol for a while, resulting in "sober intoxication": a person believes that he can drink more, 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 provoke a malfunction.
In the US, lethal cases have been reported after consuming alcohol-containing "energetics" in young people 20-25 years, the cause of death was atrial fibrillation or a heart attack. After that, a number of states banned such drinks.