Caffeine Effects, Health Benefits, Uses and Side Effects

Caffeine is the most widely used psychoactive substance in the world, consumed in the form of coffee and tea for its energy and alertness-enhancing effects.

Caffeine is a bitter xanthine alkaloid compound found naturally in some foods, most notably coffee beans. It stimulates the CNS (central nervous system), increases physical and mental activity, boosts energy metabolism and increases the amount of fluids you excrete through urine.

It is consumed electively in coffee, teas, energy drinks and supplements, mainly for increasing alertness and combating fatigue or drowsiness. [1]

Research also demonstrates that caffeine supplements have ergogenic or athletic performance enhancing benefits, can promote weight loss and may support skin, eye, and brain health.

Moderate coffee consumption has also been linked to a longer life expectancy, according to epidemiological studies. Increasing caffeine intake (within a safe dosage range) was demonstrated to significantly lower the risk of mortality.

How does caffeine work inside the body and what are the purported benefits of this natural supplement? This article will examine the effects of caffeine, how to use it safely, potential side effects and warnings about drug interactions.

Caffeine

Energy Supplement

Energy

Fitness

Alertness

How It Works:

• Boosts energy and concentration
• Increases alertness & fights fatigue
• Supports weight loss & metabolism

Dosage:

Between 50 - 200 mg per day

Safety:

Rated Likely Safe

Top Caffeine Products* ❯

View User Ratings* ❯

Caffeine Supplement Uses

According to Natural Medicines Comprehensive Database (NMCD), caffeine has been the subject of much clinical research.

It is rated as Effective by the NCMD for treating migraine, postoperative and tension headaches, and is Likely Effective for enhancing mental alertness. [2]

Further, NMCD rates caffeine supplements as Possibly Effective for a variety of health conditions, including:

• Hypotension (low blood pressure);
• Improving athletic performance;
• Gallbladder disease;
• Parkinson’s disease;
• Neonatal apnea;
• Weight loss;

NMCD states that caffeine is also Possibly Effective for asthma, diabetes, improving memory and alleviating pain. [2]

The use of caffeine has been research for other conditions including cancer pain, age-related cognitive decline, depression, OCD (obsessive compulsive disorder), hepatitis, cirrhosis, stroke and muscle soreness.

According to NMCD, there is not enough reliable evidence to rate the efficacy caffeine in these conditions. [4]

How does Caffeine work Inside the Body?

Caffeine is a methylxanthine compound that has been shown to increase stimulation of the central nervous system.

It has an excitatory effect at high dosages, causing heightened stimulation of neuroreceptors in the brain.

It works by binding to adenosine receptors in the brain, blocking this brain chemical from exerting its normal inhibitory effect on the nervous system.

Adenosine is a neurotransmitter that has a depressant effect, which means it slows down nerve cell activity by regulating the transmission of certain signals.

It is important to have a balance between excitatory and inhibitory signals in the brain and body for proper neurological and physiological functions to occur.

Adenosine is involved in the regulation of sleep and causes blood vessels to dilate, preventing over-excitation of the nervous system.

While this is an important function in the body, sometimes tipping the balance in favor of excitatory brain chemicals can have short-term benefits for focus and alertness.

Consuming coffee, tea or Red Bull works because the caffeine in these beverages gets in the way of adenosine receptors so that they cannot respond normally to the effects of adenosine.

The result is increased nerve cell signalling, constriction of blood vessels and heightened cellular metabolism. We experience this as feeling more energetic, improved cognition and improved physical performance.

Caffeine Research Effects

The University of Maryland Medical Center (UMM) reports that caffeine is not stored in the body, and rapidly crosses the BBB (blood brain barrier) to enter the brain. [1]

The half-life of caffeine is roughly 6 hours. It is 100% bioavailable after ingestion, and is converted inside the liver into theobromine, theophylline and paraxanthine. [4]

Caffeine is known to excite the CNS, as well as the heart and other muscles. It may also stimulate the pressor centers that help to modulate arterial blood pressure. [2]

Caffeine is believed to block adenosine receptors, and thereby upregulate the release of brain chemicals called neurotransmitters.

One of these brain chemicals is called dopamine, the “feel good” neurotransmitter that allows us to experience pleasure and reward. [2]

Some researchers have proposed that caffeine can also decrease serotonin, acetylcholine, adrenaline and GABA (gamma-aminobutyric acid) signaling inside the brain. [2] [4]

Although caffeine may increase mental alertness, it does not neutralize the effects of alcohol. UMM states that it is not true that having a cup of strong coffee helps to sober up after drinking. [1]

According to Drugs.com, methylxanthines are a unique class of pharmaceuticals that act as bronchodilators, and are used mainly for treating asthma. [3]

Bronchodilators relax smooth muscle and endothelium to help constricted airways dilate and function more efficiently. [2]

Like all methylxanthines, caffeine is believed to induce bronchodilation by inhibiting an enzyme called phosphodiesterase. This enzyme is known to break down a secondary messenger called cyclic AMP (adenosine monophosphate). [2]

By relaxing airways, caffeine decreases resistance and stimulates more efficient, less laborious respiration. [2]

Caffeine is often used in conjunction with analgesic (pain relieving) medicines. NMCD states that caffeine can decrease the time it takes for an analgesic to work – and increase its efficacy by as much as 40%. [2]

Further, caffeine might posses its own analgesic effects. Although these are believed not to be very potent. [4]

Caffeine is a natural diuretic. Diuretics increase the production of urine in the kidneys (diuresis) – and increase the frequency of urination. It is estimated that each milligram of caffeine ingested will cause a 1.17 mL loss of body fluids. [2]

Caffeine’s diuretic activities might help people who suffer with edema; a condition of excessive body fluids that causes swelling and discomfort. [2]

Because caffeine acts to reduce body fluids, some people think it might cause dehydration. However, one study showed that consumption of caffeinated beverages during exercise did not alter hydration status. [2]

Another study showed that routine consumption of caffeinated beverages does not significantly affect fluid status. [2]

Caffeine Mechanisms of Action

According to NMCD, some other mechanisms of caffeine action include: [2][4]

• May increase cortisol and ACTH (adrenocorticotropic hormone);
• Seems to elevate blood pressure during psychological stress;
• May contribute to insulin resistance in obese people;
• May protect dopaminergic nerves inside the brain;
• Possibly alters cardiovascular stress reactivity;
• May impair after-meal glucose metabolism;
• May cause a slight decrease in heart rate;

Caffeine may also decrease extracellular potassium, and increase intramuscular calcium concentration. It may help to prevent cardiovascular disease by inhibiting platelet aggregation, and slowing down the formation of thromboxane during blood clotting.

Caffeine may also decrease testosterone levels – and increase an estrogen ester called estrone. Caffeine may also increase levels of a protein that binds to sex hormones called globulin. [2]

Because of its apparent hormonal effects, caffeine has been researched for its effects on conditions including breast cancer, fibrocystic disease, osteoporosis, endometriosis and other conditions affected by hormone imbalance. [2]

Caffeine Health Benefits

There has been a large amount of clinical research conducted on caffeine. However, its effects on the CNS and body are not well enough understood yet to determine if caffeine can be beneficial in most conditions it has been tested in. Research continues in many areas of health.

Headache:

As stated above, NMCD rates caffeine as Effective for migraine, postoperative and tension headache.

The FDA has approved caffeine as a product suitable for combinatory use with analgesics for treating migraine headache.

Multiple studies have shown that oral use of caffeine – taken with sumatriptan, aspirin and/or acetaminophen – effectively treats migraine headache. Some evidence suggests that caffeine works better with acetaminophen and aspirin than with sumatriptan. [2]

Caffeine is used orally and intravenously for treating postoperative headache. Caffeine is also FDA-approved for preventing postoperative headache in those who consume caffeinated foods and beverages routinely. [2][4]

Oral use of caffeine combined with analgesics is also effective for treating common tension headaches. A 100 mg dose of caffeine, taken by itself, is more effective than an inert placebo, but less effective than caffeine plus an analgesic, for treating tension headache. [2]

The FDA has also approved caffeine for use with analgesics for improving pain associated with tension headache. [2][4]

Caffeine for Mental Alertness:

NMCD rates caffeine as Likely Effective for improving mental alertness. The effects of caffeine seem to be more intense in those who do not consume caffeinated products regularly, due to a tolerance forming. [2]

According to various studies, people who consume caffeinated products throughout the day seem to be less prone to decreased alertness and cognitive capacity than those who do not consume them. [2]

NMCD notes ten different studies that have shown that oral administration of caffeine improves processing speed and alertness in those deprived of sleep for long periods. However, caffeine does not seem to improve mental accuracy or performance markers. [2]

One study suggests that caffeine decreased cognitive impairment commonly associated with an antihistamine medication called chlorpheniramine (Ahist, Chlor-Trimeton). [2]

Using caffeine along with certain other dietary supplements might have synergistic benefits for improving mental alertness and performance. Some of these include taurine, L-theanine and glucose. However, not enough research has been conducted to validate this claim. [2]

Overall, caffeine is considered a powerful stimulant, and a nootropic. Some people include caffeine as part of their routine nootropic stacks because it is purported to enhance cognition, alertness, focus, attention and concentration. [2][4]

Caffeine and Athletic performance:

Does caffeine improve athletic performance? Many athletes claim that it does help them to feel more energetic, and to get mentally “pumped up” for workouts or competitions.

Concerning the clinical evidence, caffeine has been shown to affect several factors associated with athletic performance. Some of these include: [2, 4]

• Decreasing self-perceived levels of physical exertion;
• Increasing cellular thermogenesis (heat production);
• Increasing REE (resting energy expenditure);
• Increasing nonoxidative fatty acid turnover;
• Improve anaerobic exercise performance;
• Increasing lipid oxidation (metabolism);
• Increasing time to oxygen deficit;
• Increasing time to exhaustion;

NMCD cites at least 6 different studies that suggest that pre-workout caffeine doses between 2 and 10 mg/kg of bodyweight improve physical endurance by at least 14%, and increase muscle strength by 7%. [2]

Caffeine is also commonly used with ephedra to stimulate weight loss. Although ephedra has been used in traditional medicine for thousands of years, its sales in the US were banned by the FDA in 2004.

However, some studies do not show any benefits of caffeine in athletics. Currently, this stimulant is rated Possibly Effective for enhancing athletic performance. [2]

Caffeine and Diabetes:

NMCD states that total caffeine consumption is linked with a lower risk for developing type 2 diabetes mellitus. The effect seems to be dose-dependent, meaning more caffeine intake probably decreases the risk to a greater degree. [2]

One study suggested that 200 mg caffeine intake daily decreases the incidence of type 2 diabetes by 14%. [2]

Harvard Medical School compared North American men taking in 417 mg of caffeine daily to men taking in less than 37 mg/day. Researchers associated the higher intake level with a 20% less chance for developing diabetes. [2]

In the same study, North American women consuming 258 mg/day of caffeine seemed to have a 10% less chance for developing type 2 diabetes. Women consuming 530 mg/day were thought to have a 30% less risk. [2]

While caffeine seems to help reduce the risk of developing type 2 diabetes, it does not seem as helpful for treating existing diabetes.

NMCD states that a few small studies suggest that caffeine can actually reduce sensitivity to insulin in those with prediabetes, type 2 diabetes or gestational diabetes. [2]

Research on caffeine and type 1 diabetes mellitus has been conflicting. In one study, twice-daily 250 mg caffeine doses over 2 weeks seemed to decrease elevated blood glucose levels overnight in type 1 diabetics.

However, other studies have not duplicated these effects. More research is needed to determine any efficacies of caffeine for preventing or treating diabetes of any type.

Caffeine for Other Conditions:

NMCD states that there are several other conditions that caffeine is Possibly Effective for. These are: Parkinson’s disease, weight loss, asthma, hypotension (low blood pressure), pain, poor memory, neonatal apnea and postdural puncture headache. [2]

The FDA has not approved caffeine as a drug for the treatment of any of these medical conditions.

Caffeine Food Sources and Supplements

Coffee beans are the most common dietary source for caffeine. However, this alkaloid is also found in the fruits, seeds and/or leaves of more than sixty other plants. Some of these include kola nuts, cocoa beans and tea leaves. [1]

Caffeine is also added to various processed foods; including energy drinks, snacks, candies, chewing gum, cola and chocolates. [1]

This phytochemical is also added to products including over-the-counter diet pills, cold medicines and pain relievers. [1]

Various dietary supplements marketed for improving athletic performance and/or weight loss also include caffeine as one ingredient. [1]

Caffeine Dosage

According to Mayo Clinic, caffeine seems to generally safe for healthy individuals in doses equal to or less than 400 mg daily. That amount is roughly what is found in 4 cups of black coffee, or 10 cans of cola. [5]

However, NMCD states that doses more than 250 – 300 mg/day can cause tachycardia and insomnia. [2]

NMCD states that chronic use of caffeine, especially in large doses, can cause psychological dependence, tolerance, habituation and other adverse effects. [2]

NMCD states that caffeine is Likely Unsafe in very high doses. The estimated fatal dose of caffeine is between 10 and 14 grams. This would equate to roughly 175 mg/kg of bodyweight in the average human. [2]

Serious toxicity can also occur with lower oral doses. Variables including tobacco smoking, prior heavy use of caffeine and age can increase the chances for adverse caffeine effects. [2][4]

Caffeine Side Effects

Most people experience no adverse side effects after consuming between 2 and 4 cups of coffee.

However, in sensitive people, or in those who use certain medications, side effects are possible. Some of the most common include: [1, 2, 4, 5]

• Difficulty falling asleep and/or staying asleep;
• Headache and/or dizziness;
• Abnormal heart rhythm;
• Jitteriness, shaking;
• Rapid heart rate;

NMCD states that caffeine is Possibly Safe for pregnant and nursing women, at least in amounts commonly found in foods and beverages. Women who are pregnant and/or nursing should be cautious with caffeine, and self-monitor for any adverse effects. [2]

UMM states that children should avoid caffeine whenever possible, and that adolescents should be limited to 100 mg daily. [1]

Caffeine Interactions

NMCD reports dozens of possible interactions between caffeine and certain herbs, drugs, lab tests, health conditions and other foods.

Some supplements that caffeine may interact negatively with include red clover, melatonin, magnesium, kudzu, ephedra, echinacea, danshen, creatine, calcium and bitter orange. [2]

Caffeine may also interact with antiplatelet/anticoagulant herbs including angelica, clove, garlic, ginger, ginseng and turmeric. [2]

Caffeine may also interact with various types of pharmaceuticals and other drugs. Some of these include antiplatelets, anticoagulants, antidiabetics, diuretics, estrogens, nicotine, alcohol, stimulant drugs – and various others. [2]

Some of the lab assays that caffeine can affect results on include tests that measure bleeding times, catecholamine, creatine, lactate, glucose, urinary calcium and pharmacological stress. There are others as well. [2][4]

Some health conditions that this supplement may affect include diabetes, hypertension, diarrhea, epilepsy, cardiac conditions, glaucoma, osteoporosis, schizophrenia, and others. [2][4]

If you have any health condition, or use any type of prescription drugs, then it is best to discuss caffeine intake with a doctor who understands your health.

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