Myths about coffee, tea and cocoa
As a rule, 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, which have a psychostimulating effect.
According to the most common legend, the tonic properties of coffee were discovered by an Ethiopian shepherd, who noticed that goats, after eating dense leaves and dark red fruits of the coffee tree, had stopped sleeping at night. He told about this strange case to the abbot of the monastery, he decided to try the effect of unusual grains on himself and was struck by the force of the impact of the drink!
In order to maintain the vigor of the monks who fell asleep during night prayers, he commanded them to drink broth, relieving fatigue. It happened in the IX century, however, the world recognition of coffee received much later. Peter the Great brought coffee beans to Russia along with potatoes, tobacco, and other European novelties. According to historians, he was forcibly treated to “bitter” drinks by those close to him.
The history of caffeine is more transparent: the German chemist Ferdinand Runge opened it and gave us the familiar name in 1819, and in 1828 the French Pelletier and Cavant managed to get the substance in its pure form.
Four years later, the Germans Wöhler, Pfaff and Liebigh figured out the chemical formula. And reproduce caffeine in the laboratory could Herman Emil Fischer, who, incidentally, his Nobel Prize in Chemistry in 1902, is obliged including this work.
Tangle of contradictions
However, this clarity ends, and the real dark forest begins. The fact is that while there are no definitive and well-established ideas about the mechanism of action of caffeine, or about its effect on the body! Data on the doses and effects that medical students of the higher educational institutions were taught about twenty years ago as the generally accepted properties of caffeine are completely outdated nowadays.
The number of studies of coffee in general and of 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 placed on caffeine, but also to the fact that coffee is an extremely popular food product. It is not surprising that its producers and sellers are extremely interested in a positive image.
Coffee companies sponsored a huge amount of research, published mainly in not the most cited journals, sometimes there is not even practicing the review of materials by several independent experts. Mostly small groups (30–100 people) are involved in such works, information is collected using questionnaires, and there are many questions about the design of the research. But they win mass.
Suffice it to say that the results of the first truly independent and large-scale study of the effects of coffee on human health were published only in May 2012. On any information about the negative impact of coffee on health will find a dozen denials. Readers will not delve into the nuances, understand the sources of funding and methodological errors of researchers, therefore, to find truly reliable information in this thread is very, very difficult. But you can.
Drink coffee for health
Let's start with the most important thing - 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 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 of the 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 is also associated with this receptor subtype, 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 consuming coffee, after which they underwent PET with the fluorine-18 isotope (F-18-CPFPX), which does not firmly bind to the A1 receptors. The participants were then given caffeine in the form of short intravenous injections, gradually increasing the injected volume. Caffeine contacted A1 receptors, displacing F-18-CPFPX. After this, PET was repeated. The results showed that at a caffeine concentration of 13 mg / l (equivalent to 4–5 standard espresso portions), 50% percent of the 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 questionable, although scientists agree that the addiction to coffee still happens. But, as emphasized in all manuals, the addictive potential of caffeine is extremely low. That is, a person may well live without coffee, and there is no serious “breaking up” against the background of the refusal of the invigorating drink. 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, the inhibitory effect of adenosine, which now has no one to compete with, can be pronounced for some time. But the situation quickly returns to normal. Nevertheless, caffeine overdose is possible, with consequences up to a lethal outcome (theoretically). Toxicologists have calculated that a cup of espresso per 1 kg of body weight can be a lethal amount, and this dose 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 has not 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 often than those who do not drink it.
Persistent hypertension does not occur in coffee lovers, with very few exceptions - with prolonged use of more than 1 liter of drink per day, an increase in systolic pressure on “whole” 10 mm Hg is possible. 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 research does not allow to finally conclude that they are carcinogenic). In the same group, by the way, there are mobile phones, talc and almost 500 more items. Meanwhile, it turned out that lovers of invigorating drink less often suffer from aggressive prostate and breast cancer. And many research groups today are eyeing caffeine as a universal vehicle that facilitates the flow of anticancer drugs, for example, to the brain.
But some concerns were confirmed. For example, pregnant women are not recommended to exceed the daily dose of 200 mg of caffeine, as 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 leaves. In coffee, by the way, there is no teobromine at all. Theobromine was first isolated from the cocoa bean by the prominent Russian chemist A. A. Voskresensky in 1841, and in 1882 the already mentioned Nobel Prize winner Hermann Emil Fisher received a synthetic analogue.
Unlike coffee, where all 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 his addictive potential tends to zero. The main effect of theobromine is relaxation of smooth muscles. It is achieved in two ways - by inhibiting the enzyme phosphodiesterase (PDE) and reducing calcium intake through cell membranes. This effect is widely used in medicine, theobromine is a drug used to expand the bronchi, reduce peripheral vascular resistance and reduce pressure in the pulmonary circulation. It also increases blood flow in the coronary arteries, the contractility of the myocardium and increases heart rate. True, this leads to an increase in the heart's need for 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 the gene responsible for the synthesis of the cytochrome P450 CYP3A4 hepatic enzyme has been described. Horses, dogs and cats are extremely sensitive to this substance - chocolate is absolutely contraindicated for 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 method of synthetic production was proposed by his compatriot Hermann Emil Fischer (yes, that same one). However, another method of synthesis, proposed in 1900 by Wilhelm Traube, took root in industry.
Theophylline is very similar to theobromine, and the effects it causes are similar. The only difference is that theophylline has a diuretic effect. The rest is similar: relaxation of smooth muscles, expansion of peripheral vessels and increased contractility of the 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 drug. And this must be taken into account when trying to drink any medicine with tea. Thus, the effect of diuretic furosemide will increase, and the "heart" beta-blockers will work significantly worse. The instructions for theophylline section "Drug Interactions" takes a whole page.
But with respect to all three listed methylxanthines, it is better to follow 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, because he considered them harmful to health. To prove this, he conducted an original scientific study, replacing the twin criminals with a penalty for life imprisonment with the condition that the first one would drink three cups of coffee, and the second three cups of tea a day.
Each prisoner was assigned a doctor.
First the first doctor died, then the second, then in 1792 Gustav himself was killed, and both prisoners lived to a great old age.
At least, it is known that the twin, “sentenced” to tea, died at the age of 83 years, and history 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 behind it, accelerating intoxication.
But at the same time, the “anti-brake” effect of caffeine balances the depressive effect of alcohol for some time, as a result of which a “sober intoxication” develops: 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 failure.
In the United States, fatal cases have been reported after drinking alcohol-containing "energy drinks" in young people aged 20–25, the cause of death was atrial fibrillation or heart attack. After that, a number of states have banned such drinks.