Everything you wanted to know about coffee: the benefits and harms of the popular drink

It is still unclear whether coffee brings more benefits or, on the contrary, harm.

The beneficial properties of coffee

1. Coffee is invigorating

This is perhaps the most well-known property of coffee. This is explained by the fact that caffeine is a psychostimulant. When we drink coffee, the caffeine enters the bloodstream and with it enters the brain, where it blocks the neurotransmitter adenosine.

Adenosine is involved in energy transfer, inhibits alertness, and stimulates sleep. The concentration of adenosine in the body increases with each hour of wakefulness, causing drowsiness. When adenosine is blocked, the concentration of other neurotransmitters, such as norepinephrine and dopamine, increases. This is what gives the invigorating effect.

Many studies confirm that coffee improves memory, mood, reaction speed, attention, and cognitive function. So coffee invigorates us and makes us smarter.

2. Coffee enhances the body’s performance

When caffeine stimulates the nervous system, it sends signals to other parts of the body. Fat cells get the signal to break down fat deposits. Those who have recently started drinking coffee are the most effective at burning fat. According to studies, caffeine burns up to 29% of fat in thin people and up to 10% in those who are obese. When fats enter the bloodstream and are converted to free fatty acids, the body can use them as an energy source.

In addition, caffeine increases blood levels of adrenaline, which prepares the body for intense physical activity. So before your next trip to the gym, try having a cup of black coffee.

3. Coffee relieves muscle pain after a workout

According to a study, two cups of brewed coffee after a workout relieves muscle pain. During this experiment, participants drank coffee after performing eccentric muscle exercises. After an hour, they were asked to rate the intensity of their pain on a scale of 0 to 100. It turned out that coffee with caffeine significantly reduced sensitivity to pain.

4. Coffee helps fight depression

Caffeine increases the production of dopamine, the neurotransmitter responsible for movement, memory and thinking. Dopamine is also associated with the feeling of pleasure. That’s why coffee helps fight depression.

According to a study at Harvard University, women who drink coffee have a 20% lower risk of depression. Another study found that those who drink coffee are 53% less likely to commit suicide. Participants in both studies drank four cups of coffee per day.

5. Coffee is good for liver health

Some believe that coffee can protect against cirrhosis. A study by Singaporean scientists confirmed that drinking two or more cups of coffee a day can reduce the risk of developing cirrhosis by about 66%.

Other researchers found that drinking coffee can also reduce the risk of liver cancer. And decaffeinated coffee lowers liver enzyme levels in the blood.

6. Coffee may prevent gallstone formation

Gallstones are hard lumps in the gallbladder. They occur because of an improper diet (too much cholesterol), problems with the gallbladder (it does not empty completely) and due to some diseases such as cirrhosis.

Caffeine helps prevent gallstones. This was confirmed by a study in which scientists followed coffee consumption and gallstone formation in 46,000 men for 10 years. Another study involving women had the same results.

7. Coffee may reduce the risk of developing diabetes type 2

An analysis of 18 studies with 457,922 participants confirmed that each cup of coffee reduced the risk of diabetes by approximately 7%.

Coffee consumption affects sex hormone binding globulin (hGHB). This protein controls the activity of the sex hormones testosterone and estrogen, which play a role in the development of type 2 diabetes.

The authors of the study observed that there was an inverse relationship between coffee consumption and the risk of diabetes. By increasing plasma levels of hGH, coffee appears to prevent the development of diabetes.

8. Coffee reduces the risk of Alzheimer’s disease

Alzheimer’s disease appears after age 65. It is the most common neurodegenerative disease in the world. Patients gradually lose their memory, thinking skills and ability to perform the simplest tasks.

There is no cure for the disease yet. However, there are many preventive measures. These include a healthy diet, regular physical and mental exercise, and the consumption of coffee. Many studies confirm that coffee reduces the risk of developing Alzheimer’s disease by up to 65%.

9. Coffee reduces the risk of Parkinson’s disease

The second most common neurodegenerative disease is Parkinson’s disease. It develops when dopamine-producing neurons in the brain die off. Coffee consumption reduces the risk by about 30-60%. A possible reason is the positive effect of caffeine on the neurotransmitters responsible for dopamine production.

In addition, coffee may also be beneficial for those already suffering from Parkinson’s disease. According to scientists at McGill University, caffeine helps such patients control their movements.

10. Coffee protects against heart failure

Moderate coffee consumption protects against heart failure, according to research. The key word is “moderate.” It usually refers to two cups a day.

11. Coffee is the best source of antioxidants

Coffee, both with and without caffeine, contains about the same amount of antioxidants. And it’s more than in fruits and vegetables combined (in the typical Western diet). Antioxidants are substances that prevent oxidation and fight free radicals in the body. For example, they reduce the risk of oral cancer. Decaffeinated coffee also has a protective effect, but tea has none at all.

12. Coffee protects against retinal damage

One of the strongest antioxidants is chlorogenic acid. Researchers at Cornell University found that this ingredient in coffee prevents retinal cell death caused by hypoxia (oxygen deprivation) or oxidative stress (cell damage due to oxidation). The effect of chlorogenic acid was also tested on mice with damaged optic nerve. The results were the same.

13. Coffee reduces risk of colon cancer

Researchers followed 489,706 participants and found that those who drank four to five cups of coffee had a 15% lower risk of colon cancer.

14. Coffee lowers risk of skin cancer

Basalioma is one of the most common forms of skin cancer. Although not usually fatal, it causes irreversible physical skin blemishes.

A study conducted by U.S. scientists proved that caffeine consumption reduces the risk of skin cancer. Women who consumed three cups of coffee a day had the lowest risk.

Another study found that coffee may help prevent melanoma.

15. Coffee protects against cavities

At the Institute of Dental Sciences in India, scientists conducted a study and collected data from all patients who consumed coffee. They took into account the frequency of consumption, the brand of coffee, the presence or absence of additives (milk, sugar), as well as the diet and other habits of patients.

They found that those who drank about three cups of black coffee a day had the least dental problems. But sweeteners, cream and milk completely deprive coffee of its antibacterial properties.

16. Coffee can strengthen DNA

DNA chains sometimes break. Double strand breaks occur if byproducts of cellular metabolism cause damage to the DNA and block its replication. This will lead to cell death if the DNA is not repaired. And if it reconstitutes itself incorrectly, some parts of the DNA can become rearranged. Such rearrangements are usually found in cancer cells.

Scientists followed healthy men, some of whom drank black coffee and some of whom drank water, for four weeks. First, the two groups had the same number of spontaneous DNA breaks. Then there was an increase in the number of breaks among those who drank only water and a decrease among those who drank coffee. The difference was 27%.

17. Coffee reduces the risk of gout

Gout is a common form of arthritis that usually occurs in men and most commonly affects the joints of the big toes. In particularly severe cases, the joints become permanently deformed.

Researchers followed 45,000 men for 12 years and took into account what drinks they consumed (coffee, decaffeinated coffee, tea). Among the participants, 757 suffered from gout.

In the end, it turned out that increased coffee consumption reduced the risk of developing gout. Decaffeinated coffee was less effective in this case, and tea had no effect at all.

18. Coffee is rich in nutrients

Coffee contains more than just caffeine and antioxidants. Most of the nutrients rich in coffee beans remain in the drink and are absorbed by the body.

One cup of coffee contains:

  • Vitamin B2: 11% of the recommended daily allowance.
  • Vitamin B5: 6% of the recommended daily allowance.
  • Manganese and potassium: 3% of the recommended daily allowance.
  • Vitamin B3 and magnesium: 2% of the recommended daily allowance.

This amount may not seem like much, but it’s only one cup, and many people drink 3 to 4 cups a day.

Coffee beans are also rich in fiber, a healthy dietary fiber. Researchers tested different ways to make coffee (espresso, filtered, instant). The results confirmed that brewed coffee has more soluble dietary fiber than any other drink. What coffee does not have much in the way of calories (if you drink it without milk and sugar).

Harmful Properties of Coffee

Despite all its benefits, coffee is not the healthiest drink in the world. It raises blood pressure, is bad for pregnant women and is addictive. In addition, scientists have found 18 other harmful properties of coffee.

1. Coffee can lead to insomnia

Coffee gives us energy, but the same property of coffee is harmful when we try to sleep. The invigorating effect of caffeine starts to be felt 15 minutes after consumption, but it lasts much longer. It takes about six hours for the stimulating effect to wear off halfway.

If you want to get a good night’s sleep, try not to drink coffee in the afternoon. Or at least two to three hours before you go to sleep.

2. Coffee affects the effect of medicines

If you are taking any medication, be sure to ask your doctor if you can drink them with coffee. The drink may enhance, weaken or even change the effects of the pills.

For example, researchers have studied the behavior of alendronic acid (an osteoporosis treatment) when taken with water and other drinks. It turned out that black coffee and orange juice weakened the absorption of the drug by 60%. And the effect of thyroid drugs is reduced by 55% if they are taken with coffee.

In addition, the situation can be reversed. Drugs can increase the effect of coffee: you will feel a caffeine euphoria for a longer time. So be sure to consult your doctor.

3. Coffee can aggravate acid reflux

One of the symptoms of acid reflux is heartburn. This unpleasant sensation occurs when the lower esophageal sphincter (which separates the esophagus and stomach) does not close in time. Gastric juice then enters the esophagus.

Coffee is extremely acidic. If it gets into an acidic environment (gastric juice), it will cause the esophageal sphincter muscles to relax. This can cause or exacerbate heartburn. Decaffeinated coffee is also a threat. According to some studies, such coffee increases the level of acidity in the stomach by stimulating the production of the stomach hormone gastrin. And this causes the release of gastric juice.

If heartburn bothers you twice a week or more often, you should give up coffee. You should also be careful with tea, citrus juices, milkshakes and alcohol if you have heartburn.

4. Coffee can cause indigestion

A cup of coffee on an empty stomach stimulates the production of hydrochloric acid, and this can lead to serious digestive problems. Hydrochloric acid is normally produced in the stomach when food enters it, and is used to digest proteins and fats.

If too much of it is produced in one meal (eating too much fat or drinking too much coffee on an empty stomach), not enough is produced the next time and then the food is not fully digested. This can lead to bloating and stomach discomfort, and in severe cases, irritable bowel syndrome and even colon cancer. So try to avoid drinking coffee on an empty stomach.

5. Coffee can work as a laxative

Coffee stimulates the contraction of the intestinal muscles. This would seem to be a good thing, because coffee can help with constipation. But this property of coffee can also cause a number of problems, such as emptying the stomach. Then the entire contents of the stomach go into the small intestine before the food is completely broken down and digested. The nutrients from such food simply will not have time to be absorbed, and this can lead to inflammation of the intestines.

6. Coffee contains carcinogenic substances

When coffee beans are roasted at high temperatures, acrylamides can form in them. These substances are considered carcinogenic and genotoxic.

Although dangerous amounts of acrylamides are found in a variety of foods, coffee is a major source of these substances. The darker the roasted coffee beans, the more acrylamides they contain.

7. Coffee impedes platelet function

Platelets are blood cells produced in the bone marrow. They help stop bleeding by clogging a damaged vessel.

In 2008, researchers studied the effects of coffee and caffeine on platelets. Study participants consumed coffee or caffeine capsules and water. Those who drank coffee had a decreased ability of platelets to stick together. And those who received only caffeine had no change in platelet properties.

It turns out that decaffeinated coffee won’t solve this problem. And it can have serious consequences for those who suffer from anemia or other blood clotting disorders.

8. Coffee may reduce the likelihood of pregnancy

According to researchers at the University of Nevada Reno, fallopian tube activity is reduced in those who regularly consume caffeine. These tubes are used to transport eggs from the ovaries to the uterus. A study conducted on mice found similar problems in those rodents given caffeine.

9. Coffee increases cholesterol levels

Cholesterol is a fatty substance that is essential for the production of hormones and other important substances for the body. But if too much of it is secreted, it is deposited in the arteries. And this leads to various problems with the heart and blood pressure.

Coffee contains a substance that increases cholesterol, cafestol. According to one study, five cups of French-press coffee contains 30 mg of cafestol. Drinking five cups of coffee a day for four weeks would raise blood cholesterol levels by 6 to 8 percent.

The paper filters used in the coffee brewing process can help protect you from cafestol. They will trap most of the cafestol.

10. Coffee can cause osteoporosis

Osteoporosis is a bone disease in which bones lose their density and become bee honeycomb-like. It is especially dangerous for the elderly.

Calcium is essential for bone health, and caffeine reduces its absorption. With every cup we drink, we lose about 4-6 mg of calcium. According to scientists, caffeine leads to an accelerated loss of bone mineral density among older women.

11. Coffee makes us crave sweets

Caffeine increases cravings for fruit juices, carbonated and other sugary drinks (which are addictive in themselves). This was confirmed by a randomized controlled trial conducted by Australian scientists.

Participants in the study were divided into two groups: one group drank caffeinated beverages for several days, the other did not. The researchers then analyzed the participants’ diets. It turned out that participants in the first group drank 419 ml of sugary drinks per day, while participants in the second group drank only 273 ml.

12. Coffee reduces iron absorption

Iron is necessary for the production of hemoglobin. This protein, which is part of blood cells, carries oxygen from the lungs to other parts of the body. Even if your diet is rich in iron or you take supplements, your body will have less iron absorption if you drink coffee. Just 150-250 ml of coffee will reduce iron absorption by 35%.

13. Coffee can cause mastopathy

In this disease the mammary glands have lumps that increase in size and pain during menstruation. The cause of the disease is related to hormones. According to one clinical study, women who consume 30 to 250 mg of caffeine per day have a 1.5-fold increased risk of mastopathy.

14. Coffee irritates the gastrointestinal tract

For those who suffer from gastritis, ulcers or intestinal problems, doctors recommend avoiding coffee altogether. It is quite possible that it has caused the occurrence of these diseases.

One of the causes of ulcers is the bacterium Helicobacter pylori. Coffee because of its acidity corrodes the mucous membrane of the stomach, and this creates a favorable environment for bacteria. Of course, a strong immune system can protect against it, but not always.

Coffee can cause serious damage to the small intestine as well. You can get cramps, colic, constipation, or diarrhea.

15. Coffee increases anxiety and stress

Coffee stimulates the production of adrenaline, noradrenaline and cortisol. These hormones turn on the body’s “hit or run” response. It seems like a good thing, because we will feel awake and full of energy. Only this energy is produced too much, so we start to fidget and get nervous.

This is because caffeine blocks the production of gamma-aminobutyric acid (GABA). This neurotransmitter is involved in central nervous system inhibition. It relieves us of anxious thoughts. When GABA is not released, we experience stress.

16. Coffee may increase risk of miscarriage

Researchers from the National Institutes of Health and Ohio State University analyzed observational data on 500 couples. Researchers looked at the relationship between the presence of chemicals in the environment, the parents’ lifestyle and their fertility.

They found that the risk of miscarriage was higher if both partners drank more than two cups of any caffeinated beverage a day in the weeks before conception. Also, the risk of miscarriage was increased if women drank coffee in the first seven weeks of pregnancy.

17. Coffee increases blood pressure

You may have high blood pressure for years, but you may not be aware of it. But even if you don’t notice symptoms, your blood vessels and heart are still damaged, and this can lead to serious consequences (stroke or heart attack).

Italian researchers analyzed data from more than 1,200 patients between the ages of 18 and 45 with first-degree hypertension. Those who drink a lot of coffee are at risk for high blood pressure (the risk increases fourfold). Those who drink moderate amounts of coffee have a threefold increased risk.

18. Coffee can cause incontinence

Researchers at the University of Alabama found that coffee has a relaxing effect on the bladder. Daily intake of more than 200 mg of caffeine leads to urinary incontinence.


Coffee can be good for your health, but it can also be bad for you, especially if you drink too much of it. That’s why scientists recommend moderate amounts of coffee – no more than 400 mg of caffeine per day. That’s about 3-4 cups of ground coffee (or 5 cups of instant coffee). However, if you have high blood pressure, bladder or stomach problems, it’s best to avoid coffee altogether.