Most people don’t think of coffee — and the caffeine that packs its punch — as a drug, but it is, and it is possibly the most widely consumed drug in the world. In the United States, up to 90% of people in all age groups consume at least some caffeine daily, and about 50% drinking coffee every day, according to the American Migraine Foundation.
To the delight of regular coffee drinkers, the popular morning brew boasts plenty of health benefits.
Regular coffee consumption is associated with a higher metabolic rate, lower risks of Type 2 diabetes, Parkinson’s disease, coronary heart disease in women, various nervous system diseases, and suicide, according to the American Heart Association. In at least one study, caffeine was linked to a reduced risk of Alzheimer’s disease.
Of course, coffee is not for everyone, and most of these benefits should only be expected under certain conditions. For example, coffee’s health benefits are offset by added sugar and cream. Similarly, it can also be highly addictive and dangerous when consumed in excess.
Four cups of coffee, or up to about 400 milligrams of caffeine, are considered safe for most healthy adults, according to the Mayo Clinic. More than that may be considered too much. And decaf does not mean the item contains no caffeine. Decaf coffees and teas have less caffeine than the regular versions, but they still contain some caffeine, according to the U.S. Food and Drug Administration.
24/7 Tempo reviewed the long list of outcomes associated with excess coffee consumption from publications in medical journals like the Lancet, policy research organizations like the American Heart Association and American Migraine Foundation, and government sources like the Centers for Disease Control and Prevention (CDC).
Multiple studies have linked caffeine to mood and emotional problems such as anxiety and depression. Feeling restless, anxious, and/or irritated are not uncommon among people who may have had one or two extra cups of coffee. One study even suggests that people who consumed more than 1,000 milligrams of caffeine in one day showed virtually the same symptoms as people suffering from anxiety disorder.
You can’t sleep
Being a stimulant, caffeine may temporarily make people feel more alert, which is why most people drink caffeinated beverages such as coffee, tea, sodas, and energy drinks. But caffeine has that effect because it blocks sleep-inducing chemicals in the brain and increases adrenaline production, according to the National Sleep Foundation. Consuming six or more cups a day, which is considered excessive, may prevent some people from falling asleep — and the damage to the body when you do not get enough sleep can be serious.
You get stomach aches
Stomach aches are usually associated with spoiled food, but in some cases the culprit could be that cup of jo. Some research by European universities suggests that caffeine may stimulate molecular mechanisms that lead to the production of stomach acid in stomach cells, causing stomach aches. The authors of the research say dark-roasted coffees may be a better choice because they contain a compound that reduces acid production.
You also get headaches
It is relatively common to try and treat headaches with a strong cup of coffee. Caffeine is even used as a key ingredient in headache medications. However, because of the addictive properties of caffeine, headaches can also be caused by cutting back coffee consumption.
Your cholesterol is high
The culprit in coffee that affects cholesterol levels is not caffeine, but cafestol, a molecule found in coffee beans. Cafestol elevates cholesterol by blocking a receptor that is important to its regulation, according to researchers from Baylor College of Medicine. In fact, cafestol is “the most potent dietary cholesterol-elevating agent known,” according to Dr. David Moore, co-author of the study. Other research suggests that drinking five cups of French press coffee per day, each containing 30 milligrams of cafestol, for four weeks would raise cholesterol level by up to 8%.
You have temporary vision problems
Caffeine has been known to increase pressure in the eyes for a short period of time. Coffee in moderation is fine, according to the Glaucoma Research Foundation. But it is probably a good idea not to overdrink it, especially if you’re at high risk of glaucoma. Some research suggests that drinking five or more cups of caffeinated coffee a day may increase the risk of developing glaucoma, the organization notes. Additionally, caffeine may cause a spike in blood sugar levels, which may translate to blurred vision.
Your blood pressure is high
Caffeine can cause a temporary spike in blood pressure, and medical professionals are not sure why. One theory is that it blocks the production of a hormone that plays a role in the widening of the arteries. Another hypothesis has to do with caffeine’s effects on the adrenal glands. These glands release adrenaline, a hormone that causes a rise in blood pressure.
You have stained teeth
Drinking large amounts of coffee every day can lead to discolored, yellow, or stained teeth. It is so common, the side effect even has a name — coffee stains. Coffee — as well as tea and soda — gets trapped in the microscopic ridges of the enamel, the outer protective layer of the tooth, forming stains.
You’re very tired when you don’t drink coffee
Most people drink coffee as a pick-me-up drink. Chronic and excessive caffeine intake, however, may deplete energy levels after the drink’s effects wears off, according to a study of the effects of energy drinks, in which the major stimulant ingredient is caffeine. Researchers found excessive daytime sleepiness to be common the day after energy drink consumption. Caffeine triggers the sympathetic nervous system (fight or flight response), which is OK in the short-term. When it is activated repeatedly over a time, the body gets no chance to rest, leading to fatigue.
You start to hear things
Five cups of coffee a day or more in people who also feel high levels of stress may cause them to hear things, according to a study conducted by Melbourne’s La Trobe University. The study was initially researching why people who were never diagnosed with schizophrenia were showing symptoms of the condition.
You become lazy
A nine-month long study of 40 male rats conducted by researchers at the University of British Columbia, Canada, suggests that coffee may result in workers getting lazier. Researchers say the findings may apply to humans as well, especially people who use stimulants to stay alert for a long period of time, such as long-distance truck drivers.
You feel jumpy
People drink coffee to boost their alertness. Caffeine increases adrenaline levels, and when taken in high enough amounts — and these amounts vary from one person to another — jittery sensations are not uncommon, and people may feel jumpy, according to the FDA. Getting jitters and tremors as a result of excessive coffee consumption even has a name — caffeinism.
You get muscle spasms
Studies conducted so far do not establish a definitive link between caffeine and muscle cramps, but some research shows a possible connection. Stimulants can cause any muscle in the body to twitch, and coffee is a stimulant. Caffeine triggers the nervous system, which controls the contraction of skeletal muscle through nerve cells. Consumed in high amounts, caffeine can cause involuntary spasms of muscle fibres across the body, according to research out of Radboud University Nijmegen Medical Centre in the Netherlands.
You have diarrhea
Digestive issues, more specifically diarrhea, are possible side effects of drinking too much coffee. Coffee, and other beverages that have caffeine, may have a laxative effect in some people, if you drink more than three cups a day.
You have iron deficiency
Coffee — or the caffeine in it — has been shown to interfere with the body’s absorption of iron. Skipping tea and coffee drinks with meals is a common advice for anemic people. Hemoglobin, a protein in red blood cells that carries oxygen throughout the body, contains iron. Iron deficiency means less oxygen gets to the body’s cells, resulting in fatigue, weakness, and pale skin.
You gain weight around the waist
A study at the University of Western Australia in laboratory mice that aimed to show how coffee intake is beneficial to cardiovascular function ended up demonstrating that excessive caffeine consumption — the equivalent of five or six cups of coffee per day — may be linked to metabolic syndrome, which is a combination of high blood pressure, high blood sugar, excess belly fat, and high cholesterol levels. More specifically, the polyphenols, which are chemicals naturally found in plants, in the coffee made the mice retain fat in the cells. The authors do say that it is still OK to drink coffee in moderate amounts.
You develop insulin resistance
Doctors are not sure exactly why, but research has shown that excessive coffee drinking, which means high consumption of caffeine, may lower insulin sensitivity, which can lead to excessively high blood sugar level because the body cells don’t absorb as much glucose. (This can also be a sign you might have diabetes.) This is also why coffee may be a problem for diabetics as caffeine makes it harder to control blood sugar levels. (Insulin is the hormone that helps the body turn sugar into energy.)
Drinking too much coffee can cause nausea, according to the FDA. Caffeine increases the production of stomach acid, which may lead to nausea, in addition to stomach pain and acid reflux. Those who try to reduce or stop caffeine consumption may also feel nausea. Caffeine is a mental stimulant, a drug that can be addictive when consumed excessively over a long period of time, and nausea is not an uncommon symptom of withdrawal from caffeine, according to WebMD. The body struggles with the sudden change of not getting the amount of caffeine it is accustomed to.
You feel like fainting
Drinking too much coffee every day can sometimes cause hypokalaemia, a low level of potassium in your bloodstream, according to research conducted in Shinohara Hospital, Japan. Potassium is an electrolyte that carries signals to the nerves and muscles in the body. Common symptoms of low potassium levels are weakness and fatigue.
You sweat too much
While hyperhidrosis, or excessive sweating, is not a very common sign of drinking too much coffee, it is possible among people who have higher sensitivity to caffeine. After all, caffeine is a stimulant. It triggers the nervous system and speeds up thermogenesis, the process of producing heat. The internal body temperature exceeds its set point, causing people to sweat.
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