Caffeine

Caffeine is a central nervous system stimulant and the active ingredient in coffee. For most healthy people, it is not harmful to consume up to 400mg of caffeine a day.

Uses

Caffeine occurs naturally in coffee, tea, cocoa, chocolate, guarana, and many other plants, foods and drinks. Caffeine can also be taken as a supplement and may be added to other food or drinks, especially energy drinks.

Caffeine is typically used for:

• increased mental alertness
• migraines and headaches, including in over-the-counter and perscription drugs
• improved athletic performance
• to improve short-term memory
• obesity/weight loss
• less commonly, for asthma or gallbladder disease

Energy drinks

Drinks marketed as energy drinks or sometimes sports drinks typically contain a number of different stimulants, including:

• high or very high doses of caffeine
• high or very high amounts of simple sugars
• taurine
• guarana extract
• methionine
• ginseng
• other amino acids or natural stimulants

Energy drink brands include such as Spike Shooter, Pimp Juice, Red Bull, and Cocaine.

Caffeine powder

The FDA has issued a warning against the use of caffeine powder, which can provide 1200mg of caffine per 0.15 tablespoons of pure caffeine, this is three times the suggested safe daily limit and a level high enough to cause toxic effects, including seizures.

Evidence

Perscription drugs

Caffeine is FDA-approved for:

• migraine and tension-type headaches, when combined pain relief drugs
• Preventing headaches after surgery (for people who regularly consume caffeine)
• Caffeine citrate is approved for pauses in breathing that may be followed by low heart rate and low oxygen levels in newborns.

ME/CFS

Many people with ME/CFS use caffeine to improve mental alertness or concentration or to reduce fatigue in the short term, but the 2014 International Association for Chronic Fatigue Syndrome/Myalgic Encephalomyelitis primer cautions against excessive usage due to the risk of tachycardia and agitation. Consuming caffeine in the afternoon or evening is also advised against for ME/CFS patients due to the likelihood of it causing or contributing to insomnia. Adolescents and children with ME/CFS are advised to limit the use of caffeine for concentration/attention to times when it is particularly important, such as for exams, and to be aware of the caffeine found in energy drinks.

Risks and side effects

For most adults, a limit of 400mg of caffeine daily is likely to be safe, although this may not necessarily be safe long term. Just four cups of brewed coffee, ten cans of cola or two typical energy shot drinks provide the maximum recommended amount of 400mg of caffeine. Caffeine sensitivity varies greatly between people so some people will experience harmful effects at much lower doses.

High doses

Large doses of caffeine can cause serious adverse reactions, including even fatalities resulting from excessive consumption, especially in the form of "energy" drinks or caffeine powder.

Caffeine is mildly addictive, but other substances found in energy drinks are more addictive. Caffeine withdrawal is not considered dangerous.

Excessive caffeine intake causes:

• Restlessness and shakiness, sometimes called "jitters"
• Insomnia, especially if drunk/taken in the afternoon
• Headaches
• Dizziness
• Fast heart rate or racing heart
• Dehydration from increased urination
• Nervousness
• Irritability
• Anxiety
• Dependency, meaning that higher amounts of it are needed to get the same results
• Upset stomach or heartburn
• Reduced calcium absorption
• Increased blood pressure
• Muscle tremors

Interactions

Caffeine may interact with certain perscription drugs or other supplements, particularly:

• Ephedrine, which is used in decongestants
• Theophylline, a medication used to open up bronchial airways.
• Echinacea, a herbal supplement sometimes used to prevent colds or other infections

Costs and availability

Very widely available and inexpensive.

Notable studies

• 2015, Brain-derived neurotrophic factor concentration may not be depressed in chronic fatigue syndrome - (Abstract)

See also

• Guarana extract
• Taurine

Learn more

• Caffeine - MedlinePlus
• Caffine - WebMD
• Caffeine - Mayo Clinic
• Spilling the Beans: How Much Caffeine is Too Much? - FDA

central nervous system (CNS) - One of the two parts of the human nervous system, the other part being the peripheral nervous system. The central nervous system consists of the brain and spinal cord, while the peripheral nervous system consists of nerves that travel from the central nervous system into the various organs and tissues of the body.

(HR) - the number of times the heart beats within a certain time period, usually a minute

heart rate (HR) - the number of times the heart beats within a certain time period, usually a minute

See myalgic encephalomyelitis.

See chronic fatigue syndrome.

adverse reaction Any unintended or unwanted response to a treatment, whether in a clinical trial or licensed treatment. May be minor or serious.

adverse reaction Any unintended or unwanted response to a treatment, whether in a clinical trial or licensed treatment. May be minor or serious.

myalgic encephalomyelitis (M.E.) - A disease often marked by neurological symptoms, but fatigue is sometimes a symptom as well. Some diagnostic criteria distinguish it from chronic fatigue syndrome, while other diagnostic criteria consider it to be a synonym for chronic fatigue syndrome. A defining characteristic of ME is post-exertional malaise (PEM), or post-exertional neuroimmune exhaustion (PENE), which is a notable exacerbation of symptoms brought on by small exertions. PEM can last for days or weeks. Symptoms can include cognitive impairments, muscle pain (myalgia), trouble remaining upright (orthostatic intolerance), sleep abnormalities, and gastro-intestinal impairments, among others. An estimated 25% of those suffering from ME are housebound or bedbound. The World Health Organization (WHO) classifies ME as a neurological disease.