Coffee is a black, caffeinated hot beverage made from roasted and ground coffee beans, the seeds from the fruit of the coffee plant, and hot water. Coffee bushes are grown on plantations in tropical and subtropical zones. The most significant bean varieties are Coffea arabica and Coffea robusta. Only the berry-like coffee cherries, which contain the coffee beans, are picked from the coffee bushes. The beans are separated from the pulp, resulting in green coffee beans. During the roasting process, a number of roasting, bittering and coloring substances are released, which give the coffee its typical aromatic smell and taste. Different types of coffee
- Bean coffee
- Extract coffee – powdered, instant or soluble coffee that dissolves in hot water; same ingredients as brewed coffee, but lacks the aroma and fragrance typical of coffee
- Special coffee – certain ingredients are removed from the coffee for better digestibility for the stomach, gall bladder and liver; decaffeinated coffee is suitable for heart and circulation sensitive people because of the caffeine withdrawal; Schonkaffees contain no irritants and bitter substances – optionally no caffeine – more and are easy on the stomach
- Coffee from coffee substitutes – contains roasted plants and plant parts with coffee-like taste, such as barley or malt coffee and coffee from the chicory root.
Ingredients of coffee
In addition to water-soluble polysaccharides (multiple sugars), the stimulant coffee contains hundreds of unknown substances, including essential oils that give the stimulant the smell of coffee. The minerals and acids – mainly consisting of chlorogenic acid (ester of caffeic acid with quinic acid) – are largely transferred to the infusion when the coffee is filtered or brewed. The interaction of the aroma-bearing constituents, of which 2-furfurylthiol, 4-vinylguaiacol, acetaldehyde, alkylpyrazines, furanones, methylpropanol, 2-methylbutanal/3-methylbutanal and propanol are the typical components, is responsible for the versatile smell and taste of coffee. Average content of constituents of coffee (variety “Arabica”).
| Ingredients | Roasted coffee (%) | Green coffee (in %) |
| Polysaccharides (multiple sugars) | 35,0 | 46,0 |
| Fat | 17,0 | 16,0 |
| Proteins (egg white) | 7,5 | 11,0 |
| Ash | 4,5 | 4,2 |
| Lignin (insoluble dietary fiber) | 3,0 | 3,0 |
| Chlorogenic acid | 2,5 | 6,5 |
| Caffeine | 1,3 | 1,2 |
| Trigonelline (nicotinic acid-N-methylbetaine). | 1,0 | 1,0 |
| Sucrose (disaccharide/dual sugar; table sugar) | 0 | 8,0 |
Note: The data refer to the dry mass. The contained caffeine is of particular importance, as it is responsible for the invigorating as well as stimulating effect.
Caffeine
The alkaloid caffeine is a natural substance that quickly shows its effect in the human body. It is a colorless and tasteless powder used in the manufacture of medicines for its pharmacological effects. Half to three quarters of an hour after drinking a cup of coffee, the highest concentration of caffeine is reached in the blood. This high level, which is equally detectable in all regions of the body, persists for up to two hours. After that, the liver begins to remove and break down the caffeine. As a stimulating substance, it stimulates heart activity, accelerates respiration and the entire metabolism, promotes blood flow by dilating the blood vessels and has a stimulating effect on the vascular nerves in the brain. The half-life of caffeine is given as four to six hours on average. Coffee contains about 50-150 mg of caffeine per cup (150 ml), about twice as much as a cup of black tea (30-60 mg of caffeine). Filtered bean coffee and soluble coffee in particular have the highest caffeine content. A daily consumption of 400 mg of caffeine is classified by the EFSA (European Food Safety Authority) as safe for adults. The upper limit for pregnant women and nursing mothers is 200 mg of caffeine per day.For children and adolescents, an intake of 3 mg caffeine per kg body weight/day is considered safe. In this age group, caffeine is mainly ingested through the consumption of energy drinks. Overview of the caffeine content of various stimulants.
| Luxury food | Caffeine content [mg] |
| Coffee (150 ml) | 50-150 |
| Espresso (50 ml) | 50-150 |
| Black tea (150 ml) | 30-60 |
| Green tea (150 ml) | 40-70 |
| Cola drink (330 ml) | up to 60 |
| Energy drink (250 ml) | 80 |
| Milk chocolate (100 g) | 20 |
| Semi-sweet chocolate (100 g) | 75 |
However, excess caffeine is harmful to health. The lethal dose in adults is about 11 grams. To reach this level, at least 150 cups of coffee would have to be consumed or pure caffeine consumed.
Acids
Coffee contains more than 80 different acids. Their share in green coffee makes up between 4-12%. The acids influence the taste of the coffee. The chlorogenic acid (fruit acid) and caffeic acid (3,4-dihydroxycinnamic acid) should be emphasized. Both belong to the group of secondary plant compounds.Chlorogenic acid is the characteristic acid of coffee. Its content in green coffee is the highest. Chlorogenic acid is an antioxidant (protects the body from oxidative stress). Other positive effects of chlorogenic acid are: slowed absorption of glucose into the blood after a meal and lowering blood pressure in healthy people.Caffeic acid belongs to the phenolic acids (phenolic carboxylic acids). These also have an antioxidant effect and can inactivate numerous carcinogenic (cancer-causing) substances, especially nitrosamines. This reduces the risk of developing gastric carcinoma (stomach cancer). However, there are also studies showing a carcinogenic (cancer-promoting) effect of caffeic acid.Chlorogenic acid and caffeic acid are not only found in coffee, but in many other plants. Other acids found in coffee include linoleic acid, palmitic acid, acetic acid, citric acid, malic acid and oxalic acid. During the roasting process, the acids are broken down to a large extent. The slower and gentler the coffee beans are roasted, the lower the acid content.
Effects on the body
Influence on physical and mental performance
If coffee is not consumed in excessive quantities – no more than three or four cups a day – it has a positive effect on the human organism in the form of increased mental performance and improved stamina and mood without any health risk. One study also showed that caffeine consumption (at least 200 mg) improves long-term memory. Athletes use caffeine to improve their performance during training or competition. Caffeine has a mild to moderate performance-enhancing effect on strength and aerobic activities (processes that can only occur in the presence of oxygen), i.e., endurance training – caffeine does not increase anaerobic endurance (processes that occur in the absence of oxygen) as much. In the studies considered, athletes consumed 3-6 mg of caffeine per kg of body weight as a powder or in capsule form one hour before training. For a 70 kg athlete, this corresponds to the caffeine content of two to four cups of coffee (200 mg caffeine). However, the test subjects were almost exclusively young men. In high quantities, however, coffee consumption can lead to unpleasant symptoms such as impaired concentration, drowsiness, insomnia, nervousness, tension, restlessness, facial flushing, gastrointestinal disorders, muscle twitching, rapid heartbeat and cardiac arrhythmia due to the irritants and acids it contains. A stressful everyday life, habit and lack of time cause quite a few people to regularly consume the caffeinated beverage due to its stimulating effect. However, many people are unaware that coffee increases the risk of many diseases. Even two cups of coffee a day can increase the amount of inflammatory messengers in the blood of very sensitive people and thus promote heart disease. If our metabolism is disturbed by excessive amounts of caffeinated coffee, the absorption of vital substances as well as the maintenance of the vital substance content in the body can no longer be guaranteed.Increased coffee consumption often causes a lack of appetite in the body. This also contributes to the deficient supply of vital substances to the body. The human organism is considerably weakened, resulting in fatigue, headaches, absent-mindedness and poor performance. In order to get out of this performance low again, quite a few people reach for coffee. This causes however the opposite and aggravates the symptoms. If people consume particularly high amounts of caffeinated coffee during the day, the nervous system is strained, resulting in nervous tension and depression on the one hand and poor, restless sleep with difficulty falling asleep, frequent awakenings – sleep disturbances – and shortened sleep duration on the other. As a nitrogen-containing compound, caffeine is able to block the hormone N-acetyltransferase, which is responsible for the production of the sleep hormone melatonin. Melatonin synthesis is thus inhibited. If a cup of caffeinated coffee is consumed before bedtime, those affected show only low concentrations of melatonin in their blood during the night – in contrast to drinking decaffeinated coffee. As a result, the sleep rhythm is permanently disturbed.The physical as well as mental performance necessary for the day is severely impaired in this case.
Vegetative nervous system
Since caffeine stimulates the autonomic nervous system – especially the sympathetic nervous system – there is an increased release and formation of the stress hormones adrenaline and noradrenaline. An increased concentration of these hormones in the blood can trigger high blood pressure (hypertension), an accelerated pulse (tachycardia) and migraine attacks. During the migraine state, the blood vessels in the head constrict and then dilate again. This is followed by headaches, nausea, and sensitivity to light or noise [6.2]. In the case of sudden caffeine withdrawal, for example when switching to decaffeinated coffee, migraine-like symptoms may manifest as withdrawal symptoms, but also drowsiness, low mood, headache, fatigue, poor concentration, and growing cravings for coffee [6.2].
Coffee consumption and disease
Coffee and other caffeinated beverages in higher quantities should not be consumed under any circumstances when suffering from diseases.If a person suffers from gallstones, coffee – even decaffeinated – can cause spasmodic, violent contractions of the gallbladder, which increases the pain caused by gallstones irritating the inner wall and can lead to inflammation [11.2. ].Caffeinated beverages should also be avoided especially by people with sensitive stomachs, sleep disorders, cardiac arrhythmias, as well as with hyperthyroidism. Excessive coffee consumption leads to the following adverse health effects:
- Poor concentration and performance
- Sleep disturbance (insomnia)
- Headache (cephalgia)
- Nervousness, nervous tension
- Restlessness
- Fatigue
- Mood swings, depression
- Gastrointestinal disorders, heartburn, gastric ulcer (Ulcus ventriculi), diarrhea, biliary colic, constipation.
- Muscle twitching, cramps
- Heart palpitations and arrhythmias, coronary artery disease (CAD).
- Elevated serum cholesterol levels as well as triglyceride levels [6.1., 39]
- Increased homocysteine serum levels and resulting circulatory disorders, atherosclerosis – increased risk of heart attack (myocardial infarction) and stroke (apoplexy) – memory impairment, premature aging.
- Increased risk of hypertension, myocardial infarction as well as apoplexy.
- Migraine attacks
- Hypoglycemia (low blood sugar)
- Sterility
Effects on the stomach
In some people, heavy coffee consumption causes stomach problems because the stimulant, regardless of caffeine content, stimulates the formation of acid in the stomach. This increases peristalsis (motility) of the gastrointestinal (GI) tract and contraction of the gallbladder.Stomach-sensitive people react as a result of high coffee consumption with heartburn, stomach cramps, biliary colic, diarrhea (diarrhea), or even ventriculi ulcer (stomach ulcer). High amounts of caffeine damage the stomach wall by breaking down the protective layer of mucosal cells due to chemical burns. The result is a ventricular ulcer (stomach ulcer) with subsequent pain, nausea (nausea) and possibly bleeding.The stomach irritation is mainly due to the chlorogenic acid of the coffee as well as tannins and bitter substances. The amount of chlorogenic acid can be reduced by special roasting processes. Gastric patients and people with a sensitive stomach should consider the following recommendations:
- Prefer coffee made from 100% Arabica beans – Arabica beans (Coffea arabica) contain less chlorogenic acid than Robusta beans (Coffea canephora).
- Buy coffee directly from a roaster and value a slow and gentle roasting.
- Espresso is better tolerated by people with sensitive stomachs than filter coffee, because the short extraction time leaves a large part of the acids in the espresso powder. In addition, espresso beans are roasted stronger and thus contain fewer acids.
- Decaffeinated coffee is often better tolerated because it contains fewer irritants.
- Enjoy coffee with milk or coffee cream. The milk acts as a buffer in relation to the acids, so that the coffee becomes milder. By using low-fat or partially skimmed milk, the coffee flavor is well preserved.
- Drink a glass of water with every cup of coffee! So the overacidification of the stomach can be counteracted.
- Do not drink coffee on an empty stomach, because coffee increases the contraction of the stomach, which makes it more likely to stomach pain when empty.
- Do not leave coffee in the thermos for too long: The longer coffee is kept warm, the more acids are produced.
Hypoglycemia (low blood sugar)
Coffee, due to its caffeine content, also affects the glucose serum level by favoring its lowering (hypoglycemia). Under these circumstances, our body also experiences an increased release of adrenaline and noradrenaline. Typical symptoms resulting from increased amounts of stress hormones in the blood and a low serum glucose level are irritability, anxiety, mood swings, physical as well as mental exhaustion, and palpitations.
Fertility (fertility)
2-3 cups of coffee daily increase fertility in men and may have an aphrodisiac effect, although only slightly.However, excess coffee (more than 3-4 cups) may decrease fertility in women because caffeine decreases the rate of fertilization [11.1].
Lipid metabolism (fat metabolism)
Brewed, unfiltered coffee, in contrast to filtered coffee, contains a fat-soluble fraction present in coffee oil – diterpenes such as cafestol and kahweol – that increases cholesterol levels as well as triglyceride levels [6.1, 39]. Significantly, these negative effects were observable with coffee that also contained caffeine.
Other effects
The coffee oils in the stimulant cause an increase in serum homocysteine levels in the blood. In increased concentrations, the body’s metabolic product homocysteine accelerates the storage of fats in the vessel walls, causing blood vessels to constrict and circulatory problems to occur. The increase in cholesterol and homocysteine levels promotes the occurrence of a heart attack (myocardial infarction) or stroke (apoplexy), especially in patients at risk or with heart disease. Women who drink a lot of coffee have an increased risk of fracture (risk of bone fractures). The opposite is true for men.
Protection against numerous diseases
Tumor diseases
Regular coffee consumption reduces the risk of developing liver cancer by more than half. Women who drink 1-3 cups of coffee daily have a lower risk of developing endometrial cancer (cancer of the uterus). The same is true for mammary carcinoma (breast cancer). In men, moderate regular coffee consumption reduces the risk of prostate cancer (prostate cancer). It is possible that daily coffee consumption of four cups or more improves the prognosis of stage III (advanced) colon cancer (colorectal cancer) and reduces the risk of recurrence. However, these observations were made as part of a study conducted for other reasons. Studies specifically investigating the effects of coffee consumption on existing colon carcinoma (colorectal cancer) have yet to be conducted. Coffee drinkers are less likely to develop tumors in the oral cavity.Other preventive effects
It has been observed that a daily coffee consumption of two or more cups reduces the mortality of non-viral liver cirrhosis. Researchers attribute this protective (protective) effect to the bioactive compounds contained in coffee. The risk of developing cirrhosis can also be reduced by half by drinking two cups of coffee a day. Similar findings have been observed for alcohol-related cirrhosis. Coffee consumption (more than 6-7 cups daily) reduces the risk of developing type 2 diabetes mellitus by about 50%. In another study, people who drank more than 11 cups of coffee a day had a 67% lower risk of developing type II diabetes mellitus compared to non-coffee drinkers. The ingredients of coffee responsible for this preventive effect have not yet been fully clarified. Presumably, caffeine and theophylline in particular, as well as caffeic and chlorogenic acid, trigonelline and nicotinic acid, and coffee antioxidants, have an effect on glucose and insulin metabolism and thus reduce the risk of type 2 diabetes. While caffeine and theophylline increase insulin production by stimulating pancreatic cells (cells of the pancreas), chlorogenic, caffeic, and nicotinic acids, as well as trigonelline, prevent hyperglycemia (high blood glucose) and hyperinsulinemia (a condition in which blood concentrations of the hormone insulin are elevated above normal levels) by inhibiting glucose-forming enzymes of the small intestine, among other factors. Moderate coffee consumption (1-3 cups of coffee per day) reduces the risk of apoplexy (stroke). High caffeine consumption (600 mg of caffeine, equivalent to about 15 cups of espresso) reduces the risk of tinnitus (ringing in the ears) by about 15%. Coffee drinkers are less likely to suffer from gout and nephrolithiasis (kidney stones). Coffee consumption can reduce the risk of developing the neurodegenerative disease Parkinson’s disease. This is due to a SNP (SNiP) in the gene GRIN2A. SNP (SNiP) stands for “single nucleotide polymorphism” and means that there is a variation of a single base pair in a DNA strand. SNPs provide information about the genetic basis of diseases. A group of researchers found that the presence of the SNP rs4998386, in the allele constellation CT or TT, in the gene GRIN2A in combination with drinking coffee reduces the risk of developing Parkinson’s disease (no data on percentages). Regular high coffee consumption is associated with a reduced risk of death. In the European long-term study EPIC (European prospective investigation into cancer and nutrition), men who drank a lot of coffee (> 580 ml/day) had a 12% lower mortality risk (risk of dying) during the period studied (16.4 years) than people who did not drink coffee. For women, this figure was 7%. This is attributed to a reduced risk of lethal gastrointestinal diseases. Women also experienced fewer deaths from cardiovascular and cerebrovascular diseases. Furthermore, frequent coffee drinkers had better liver values (alkaline phosphatase (AP), alanine aminotransferase (ALT, GPT), aspartate aminotransferase (AST, GOT), gamma-glutamyltransferase). Women also had lower levels of lipoprotein (a), C-reactive protein (CRP) and HbA1c.That coffee consumption alone is responsible for these associations cannot be conclusively stated. However, the researchers conclude that moderate coffee consumption, that is, 3 cups per day, is not harmful to health but is more likely to have beneficial effects.
Coffee consumption and micronutrients (vital substances)
Vitamin C, calcium and magnesium
Coffee has a diuretic effect. It stimulates the function of the kidneys via the stronger blood circulation and thus forms more urine. More water, vitamins and minerals are excreted from the body. Excessive caffeine intake thus increases the excretion of vitamin C, calcium and magnesium with the urine.Since the minerals calcium and magnesium are responsible for building bones, the structure and stability of the bones are strongly negatively affected in the case of an undersupply. The risk of osteoporosis increases [6.3]. Furthermore, muscle cramps and disturbances in heart function occur with magnesium and calcium deficiency.If there are high amounts of calcium in the urine, the likelihood that kidney stones may form increases. Such stones – consisting of calcium and oxalate – cause severe pain in the lower back or in the ureter, where they cause irritation due to their hard substance [6.4. ].If too much of the antioxidant vitamin C is flushed out of the body, resulting in deficiencies, there is only insufficient protection against the free radicals that damage the organism. In addition, the risk of tumor and heart diseases increases.If the loss of water due to coffee consumption is not counteracted with sufficient fluid intake, constipation is the result.
Vitamin B6
In particular, vitamin B6 status is also affected, because regular coffee drinking can cause vitamin B6 deficiency in our body. Because this vitamin is responsible for many organs, or rather areas, in the body, several disorders in the organism can occur at once when deficiencies arise. Injuries occur in the area of the face – painful cracks at the corners of the mouth and on the lips – as well as in the area of the oral cavity – aching tongue, inflamed throat. Furthermore, insomnia, increased irritability, nervousness, sensitivity disorders and depression are often the result of low vitamin B6 levels [13.1]. If our largest organ, the skin, is insufficiently supplied with vitamin B6, inflammations appear especially around the nose, mouth, ears and genitals in the form of reddened, scaly, itchy as well as painful patches.
Iron
The tannins in coffee inhibit iron absorption and impair the availability of dietary iron. If people drink coffee frequently, iron deficiencies can develop in the body, causing anemia, rapid fatigue, high susceptibility to infection, and inflammation [13.2]. Excessive coffee consumption – vital substance deficiency.
| Vital substance | Deficiency symptoms |
| Vitamin C |
Decreased oxidation protection increases the risk for
|
| Vitamin B6 |
|
| Calcium |
|
| Magnesium |
Increased risk of
|
| Iron |
|
