Caffeine is a bitter, white crystalline xanthine alkaloid that is a stimulant to the central nervous system and one of the most consumed psychoactive drugs in the world. Caffeine stimulates the central nervous system by blocking adenosine receptors.
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There are many benefits to caffeine consumption. Caffeinated drinks are widely popular because they increase alertness, boost energy, and improve mental function. Different sources estimate average per-capita consumption of caffeine ranges from 111 to 549 milligrams daily, with an average level of about 300 milligrams per day in Western Europe.
Caffeine was first isolated by the German chemist Friedlieb Ferdinand Runge in 1819. He was researching coffee as a medicine when he discovered the substance. The first caffeine pills were invented in the 1960s and sold as micro tablets that dissolve under the tongue. In 2003, 14,000 tons of caffeine were consumed around the world.
More than 80% of people in North America consume caffeinated drinks every day, and 90% of people worldwide consume caffeine in some form on a daily basis. Caffeine is sometimes added to cold remedies even though there is no evidence to support its effectiveness in treating flu symptoms: however, it does appear to reduce the cold duration by about 24 hours. It is also available in some over-the-counter cold and flu remedies.
Caffeine is a mild diuretic, meaning it promotes urination. It increases the amount of urine produced by the body but does not have any known affect on blood pressure or volume. Some people experience headaches when they consume caffeine, but most can tolerate moderate to high doses of caffeine (300 milligrams daily), according to the Mayo Clinic. The American Psychiatric Association states that 200 milligrams of caffeine are an "approximate level below which only a few individuals experience adverse effects."
Caffeine may help increase energy, improve mood and performance, and enhance physical endurance during tasks requiring sustained attention and high decision-making skills.
However, some users report that the consumption of caffeine makes it difficult to sleep. Caffeine may also be a factor in some cases of sleeping disorders such as insomnia and hypersomnia.
Caffeine can cause signs of dependence and withdrawal symptoms when taken continually. It should be consumed only for a limited period and under medical supervision.
Caffeine has been used to treat several conditions, including insomnia, Parkinson's disease, anxiety disorders, depression, attention deficit hyperactivity disorder (ADHD), hypertension, headaches, menstrual cramps, and osteoporosis. The effects on these conditions are usually short-lived.
Many people consume caffeine to improve performance and minimize fatigue. A placebo-controlled double-blind trial involving 156 students found that caffeine gave a slight but detectable increase in the number of problems solved at a math examination, although it was not statistically significant. The single hypothesis contrasts the idea that these effects are due to increased performance in the relevant task, with another hypothesis that they are due to increased focus and concentration.
Caffeine can cause insomnia when consumed for long periods of time. The stimulation of the brain is not sufficient to account for this effect, and other biological factors must be involved.
Caffeine can cause headaches, including migraine headaches when taken in large doses or used for prolonged periods of time (over about 4 weeks). Some caution should be taken when taking caffeine in large quantities, particularly for those who suffer from headaches in the first place. The exact mechanism is not clear but may involve cortisol and adrenaline. In larger doses, caffeine can cause restlessness, anxiety, and panic attacks. Caffeine overdose symptoms are nausea, vomiting, muscle tremors and cramps in the hands or feet, irregular heartbeat, high blood pressure, or seizures.
Many people use caffeine as a stimulant to improve the performance of tasks requiring sustained attention and complex reasoning skills. There is some evidence to suggest that caffeine can improve performance on simple tasks such as reaction time and vigilance but research has not been done with either normal or clinically deficient populations.
Some studies indicate that caffeine can improve short-term memory and recall when used in moderate doses (200–600 mg). It also reduces the rate at which information is forgotten, making it more difficult to forget a message. However, since it does not increase the ability to learn new information it should be used only when necessary.
Caffeine use can improve athletic endurance, depending on dosage and the length of time one has been regularly using the drug. It may help athletes remain alert when feeling fatigued and recover from injuries more quickly. However, it is not an ergogenic aid (a substance that enhances physical performance) and does not increase maximum oxygen uptake or improve time to exhaustion during maximal exercise. It also has the potential to cause harm to the athlete.
To be effective as a performance enhancer, caffeine must be consumed several hours before the event, due to the half-life of caffeine in the body (see below). It has been shown that significant amounts of caffeine—168 mg—can enhance exercise performance in elite rowers, but had no effect on amateur rowers.
Even in research studies that show improved performance, there are risks associated with using caffeine as a stimulant. Caffeine may have the ability to over-stimulate the central nervous system, resulting in nervousness, restlessness, loss of focus, and attention span among other symptoms.
The most common adverse effects of caffeine are heart palpitations (tachycardia), anxiety, upset stomach, nausea, and quick connection to high blood pressure. In high doses, it can cause vomiting, sweating, seizures, and even death.
Some people use caffeine as a diuretic; however, this practice may be dangerous in some cases. Large doses of caffeine may increase blood pressure, which can lead to strokes and heart attacks. Though most people do not experience side effects from caffeine, some individuals have experienced more serious consequences from its use when they consumed too much. Though no deaths have been directly linked to caffeine overdose, several fatal cases of cardiac arrest are known to occur due to the consumption of excessive amounts of the drug.
A person's tolerance level for caffeine can vary considerably. If a person consumes large amounts daily (twice what is considered "low," 400 mg or less) over a long period (2–3 months) then this amount would be equal to about two cups of coffee per day. If the same person is consuming low amounts (less than 200 mg per day) for a shorter period (2–3 days) they would be considered "slow" on caffeine tolerance, and a blood test would reveal their levels similar to someone drinking coffee several times per day—that is, 400 mg per day.
Caffeine is found in over 500 plant species. The most popular sources of the drug are coffee beans, tea leaves, and kola nuts. Caffeine can be extracted from coffee beans to get a good cup of joe. In the United States, roughly 90 percent of the annual caffeine production comes from kola nuts processed in Africa and Asia.
Caffeine is a stimulant drug, often consumed to increase alertness. It is found in coffee, tea, hot chocolate, and energy drinks. It can also be purchased as a pharmaceutical drug for use in chest rubs and inhalers.
The main effects of caffeine are increased activity and feelings of well-being. Other effects may include nervousness, insomnia, headaches, irregular heart rhythm, or breathing problems (in susceptible people).
The amount of caffeine needed to produce desired effects varies from person to person. The desirable pharmacological effects may vary from one individual to another. What causes some individuals to consume large quantities on a daily basis can cause addiction in others when consumed in smaller amounts over shorter periods of time.
During the breakdown of caffeine, l-theanine is formed. This compound has been shown to have a variety of physiological effects in both humans and animals which may underlie its reported benefits. The effect on sleep-wakefulness is described below.
Caffeine affects the brain principally by blocking adenosine receptors, thereby increasing alertness and attention. It also increases focus and mental energy and may slow down reaction time in some cases. Caffeine does not generally affect heart rate or blood pressure but does increase the blood supply to muscles. It also affects the brain areas associated with emotions, causing feelings of alertness and well-being.
Caffeine has no effect on memory or basic cognitive processes. Some researchers believe that caffeine can help improve performance on tasks requiring sustained attention and complex reasoning skills, including simple tasks such as reaction time and vigilance, as well as more complex ones such as short-term memory and recall. There is some evidence to support this claim; however, research has not been done with clinically deficient populations to date.
The majority of research studies have been single-dose studies with a few multiple-dose studies (in which the two doses differ). Caffeine may increase blood pressure in some individuals. If an individual has high blood pressure, the effects on blood pressure may be amplified in these people.
Caffeine can also cause insomnia or a general difficulty sleeping by stimulating the brain and nervous system. That said, it can also help the user fall asleep when taken later in the day.
Many consumers of caffeine have experienced withdrawal symptoms when they stop consuming caffeine after prolonged daily consumption. Caffeine withdrawal symptoms may include headache, fatigue, depressed mood, and difficulty concentrating. These symptoms usually start within 12-24 hours after ceasing caffeine intake and about half of individuals experience nausea as well. Although withdrawal headaches are often related to caffeine intake, withdrawal from caffeine has not been definitively established.
Caffeine in Pregnancy
There is no definitive evidence that moderate caffeine intake during pregnancy harms the fetus. However, some studies have shown that regular consumption of caffeine during pregnancy can cause withdrawal symptoms in the infant (e.g., jitteriness, irritability, and restlessness).
Studies have shown that children of mothers who consume caffeine may be more likely to have behavioral problems, including attention deficit hyperactivity disorder and autism spectrum disorders. The reason for this correlation does not appear to be related to caffeine, but rather an effect of low birth weight or other maternal factors also associated with higher rates of these disorders. Regardless of the mechanism for this association, it remains a significant concern as it can significantly impact an individual's health as an adult.
Sources of Caffeine
The most common sources of caffeine are coffee, tea, soft drinks, energy drinks, chocolate, and pain relievers. Foods that naturally contain caffeine include chocolate, cocoa beans, kola nuts, guarana berries, and yerba mate. Caffeine is also added as an ingredient to processed foods such as ice cream and some brands of cola.
Caffeine levels in commercially available products may vary due to the manufacturing process or other factors. If a person has been diagnosed with a cardiac condition that makes them especially sensitive to caffeine they should check any product labels for amounts before consuming them. Caffeine can also be found in the following foods:
Coffee beans and some teas, including green tea, guarana, and mate, contain caffeine. Other sources include yerba mate, cacao nibs, chocolate, cocoa powder, coffee substitutes (dietary supplements), or energy drinks. The amount of caffeine in a cup of coffee depends on many factors: how strong the coffee is, how much sugar or cream is added, and how the coffee is brewed.
Benefits of Caffeine
Caffeine may have several benefits including the following:
Energy: Caffeine is the most popular stimulant in the world and it has long been used as an energy source. It stimulates the central nervous system, which can increase alertness, focus, and endurance. In some cases, people take caffeine to help reduce fatigue or prevent night sleepiness caused by some sleeping pills or by staying up late at night.
Caffeine may be able to improve exercise performance due to its stimulatory effects. It may also slow the rate at which caffeine is removed by the body during exercise, which will prolong the effects of the caffeine.
Increased Alertness: Caffeine can help improve alertness and alertness may be especially helpful during stressful times. It can even improve performance in those who are extremely fatigued, and to some extent, fatigue can make it difficult to perform at a high level.
Heart health: Caffeine can have a positive effect on people with high blood pressure or heart failure. Some studies suggest that it may reduce blood pressure in some individuals with hypertension (high blood pressure), especially if they are already on medication for their condition.
Improves reaction time and wakefulness: caffeine has been shown to improve mood, alertness, and performance in both the young and elderly. It can enhance memory, but it is not clear whether it improves learning.
Increases energy expenditure: Caffeine can increase energy expenditure by 3-11% when compared to placebo.
Natural Painkiller: However, caffeine is not a natural painkiller as coffee may make you think. A study from 2002 shows that the effects of caffeine are similar to that of the nonsteroidal anti-inflammatory drugs (NSAIDs). NSAIDs are commonly used to treat arthritis and it was found that both caffeine and some NSAIDs work similarly to reduce swelling, pain, and inflammation.
Caffeine may be able to reduce the symptoms of menopause. Most of the research on this subject suggests that caffeine has no effect on menopausal symptoms; however, a few studies indicate that it may improve hot flashes or night sweats.
Caffeine may help reduce the risk of cardiovascular disease due to its ability to favorably affect blood pressure.
The elderly tend to have low levels of blood pressure and they have often been prescribed medications for this condition. Caffeine can help improve blood pressure in this population due to its effects on blood vessel tone (vasodilation).
Aerobic Exercise: Caffeine can increase energy levels, performance, and endurance during aerobic exercise.
Heart Health: Caffeine can improve the health of people with high blood pressure and heart failure.
Muscle Pain: A systematic review of many studies and case reports concluded that caffeine improves muscle pain due to various causes including injury, tension soreness, and fibromyalgia. These results show that caffeine is more effective than a placebo for reducing muscle pain.
Insomnia: Although most people think that coffee is a very important factor in insomnia, research does not indicate that coffee drinking increases insomnia or sleep disturbance.
Furthermore, some research has shown that caffeine can improve insomnia or the ability to fall asleep. Caffeine seems to be more effective for improving sleep quality in those who are tired or sleepy at night as well as those with difficulty falling asleep.
Pain: Caffeine can reduce pain associated with headaches. Recent studies show that caffeine is even more effective than aspirin to relieve migraine pain and the effects of caffeine were evident within 15 minutes of taking the medicine and lasted for about 4 hours.
A 2009 study suggested that caffeine has a role in treating pain and that it may be useful for treating chronic pain, although more research is needed.
Allergies: Caffeine can reduce the symptoms of allergic rhinitis (nasal allergies).
Caffeine may help reduce the symptoms of asthma due to its effects on blood flow to the airways.
In high doses or as people who are sensitive, it can cause an irregular heartbeat. This is more likely in those with low levels of magnesium and potassium in their body or who have heart abnormalities. In most cases, people being treated for anxiety or depression use caffeine safely without any adverse side effects.
Caffeine Side Effects
In therapeutic doses, caffeine stimulates the central nervous system and can have a positive effect on learning, memory, concentration, and reaction time. However, caffeine can also negatively impact these functions in high doses or when taken regularly over an extended period of time.
Caffeine consumption during pregnancy may lead to miscarriage or stillbirth.
Insomnia: Excessive caffeine intake may cause difficulty sleeping and even insomnia in some users.
Tolerance: The human body tends to build up a tolerance to high doses of caffeine which is often seen as one of the leading causes behind caffeine withdrawal symptoms during cessation attempts.
Caffeine is also effective when taken before exercise because it increases alertness and endurance.
Although caffeine overdose is unlikely to cause death, it can lead to serious adverse health effects. The most common adverse effects of caffeine intake include the following:
Nausea, vomiting, diarrhea, increased heart rate, anxiety, irritability, tremors, palpitations (dizziness), headaches, edema (swelling), tachycardia (fast heartbeat), and restlessness.
Stomach pain or jitters: Some people experience a temporary stomach upset after consuming caffeinated products or a sudden spike in blood caffeine levels due to irregular dosing.
Caffeine has been reported to have negative effects on the fetus. In humans, caffeine may cause severe withdrawal symptoms in the newborn baby, including decreased heart rate and breathing movements.
Caffeine can also have an effect on lactation; it is unknown whether it can harm a developing baby.
In rare cases, people suffering from extreme allergies to caffeine may experience severe allergic reactions after consuming products containing caffeine. These reactions are usually very serious and may even be life-threatening. Some of the symptoms include difficulty breathing or swallowing, wheezing or shortness of breath, rapid heartbeat or irregular heartbeat, vomiting or diarrhea (unhealthy), dizziness, or blurred vision.
If an individual suffers from a cardiac condition (e.g, high blood pressure or heart failure) they should check the product labels and perhaps limit or avoid caffeine intake. Additionally, the amount of caffeine a person consumes may be too high for their specific situation.
Some individuals react negatively to caffeine as part of withdrawal symptoms from other prescription drugs, over-the-counter medications (e.g., asthma drugs), or illicit substances (e.g., cocaine). It is not necessarily considered safe to discontinue these medications abruptly without medical supervision; the withdrawal symptoms can be serious and potentially life-threatening if not treated correctly.
Caffeine overdose is extremely unlikely to cause death, but it may lead to serious adverse health effects.
Symptoms of caffeine overdose include the following:
Diarrhea, dehydration, stomach pain or upset, nausea or vomiting, fast heartbeat (tachycardia), increased blood pressure (hypertension), muscle tremors, and anxiety. Some people experience a combination of these symptoms when they consume too much caffeine.
A lethal dosage of caffeine in humans has not been identified. Moderate overdoses are unlikely to cause death; however, they can lead to serious adverse health effects. Symptoms of moderate overdose include confusion, agitation, headache, tachycardia (fast heart rate), and vomiting.
A moderate overdose can also lead to dehydration, slow heartbeat, muscle tremors, unsteadiness, palpitations (feeling like you are going to pass out), and insomnia. Some people experience a combination of these symptoms after consuming too much caffeine.
If an individual consumes too much caffeine and experiences any adverse effects they should contact their doctor or emergency services immediately. An overdose may also require emergency or medical attention in serious cases.